diff --git a/src/aa-path-symex/locs.h b/src/aa-path-symex/locs.h
index 9d5f45730fc..75e0ae29f7e 100644
--- a/src/aa-path-symex/locs.h
+++ b/src/aa-path-symex/locs.h
@@ -104,12 +104,4 @@ class target_to_loc_mapt
   mapt map;
 };
 
-#define forall_locs(it, locs) \
-  for(locst::loc_vectort::const_iterator it=(locs).loc_vector.begin(); \
-      it!=(locs).loc_vector.end(); it++)
-
-#define Forall_locs(it, locs) \
-  for(exprt::operandst::iterator it=(expr).loc_vector.begin(); \
-      it!=(locs).loc_vector.end(); it++)
-
 #endif // CPROVER_AA_PATH_SYMEX_LOCS_H
diff --git a/src/aa-path-symex/path_symex.cpp b/src/aa-path-symex/path_symex.cpp
index 6ea307ca058..83e56461136 100644
--- a/src/aa-path-symex/path_symex.cpp
+++ b/src/aa-path-symex/path_symex.cpp
@@ -10,7 +10,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/arith_tools.h>
 #include <util/simplify_expr.h>
 #include <util/byte_operators.h>
-#include <util/i2string.h>
 #include <util/pointer_offset_size.h>
 #include <util/expr_util.h>
 #include <util/base_type.h>
@@ -319,7 +318,7 @@ void path_symext::symex_malloc(
 
       symbolt size_symbol;
 
-      size_symbol.base_name="dynamic_object_size"+i2string(dynamic_count);
+      size_symbol.base_name="dynamic_object_size"+std::to_string(dynamic_count);
       size_symbol.name="symex::"+id2string(size_symbol.base_name);
       size_symbol.is_lvalue=true;
       size_symbol.type=tmp_size.type();
@@ -338,7 +337,7 @@ void path_symext::symex_malloc(
   // value
   symbolt value_symbol;
 
-  value_symbol.base_name="dynamic_object"+i2string(state.var_map.dynamic_count);
+  value_symbol.base_name="dynamic_object"+std::to_string(state.var_map.dynamic_count);
   value_symbol.name="symex_dynamic::"+id2string(value_symbol.base_name);
   value_symbol.is_lvalue=true;
   value_symbol.type=object_type;
diff --git a/src/aa-path-symex/path_symex_state.cpp b/src/aa-path-symex/path_symex_state.cpp
index 08397535741..c0d316ced05 100644
--- a/src/aa-path-symex/path_symex_state.cpp
+++ b/src/aa-path-symex/path_symex_state.cpp
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/arith_tools.h>
 #include <util/expr_util.h>
 #include <util/decision_procedure.h>
-#include <util/i2string.h>
 
 #include <ansi-c/c_types.h>
 
@@ -328,7 +327,7 @@ exprt path_symex_statet::instantiate_rec(
 
     if(statement==ID_nondet)
     {
-      irep_idt id="symex::nondet"+i2string(var_map.nondet_count);
+      irep_idt id="symex::nondet"+std::to_string(var_map.nondet_count);
       var_map.nondet_count++;
       return symbol_exprt(id, src.type());
     }
diff --git a/src/aa-path-symex/var_map.cpp b/src/aa-path-symex/var_map.cpp
index a487db47bfd..941a8645a6f 100644
--- a/src/aa-path-symex/var_map.cpp
+++ b/src/aa-path-symex/var_map.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <util/symbol.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/prefix.h>
 
 #include "var_map.h"
@@ -115,5 +114,5 @@ Function: var_mapt::var_infot::ssa_identifier
 irep_idt var_mapt::var_infot::ssa_identifier() const
 {
   return id2string(full_identifier)+
-         "#"+i2string(ssa_counter);
+         "#"+std::to_string(ssa_counter);
 }
diff --git a/src/analyses/ai.h b/src/analyses/ai.h
index af93bef3a8e..41838836da3 100644
--- a/src/analyses/ai.h
+++ b/src/analyses/ai.h
@@ -280,7 +280,7 @@ class ait:public ai_baset
   }
 
 protected:
-  typedef hash_map_cont<locationt, domainT, const_target_hash> state_mapt;
+  typedef std::unordered_map<locationt, domainT, const_target_hash> state_mapt;
   state_mapt state_map;
 
   // this one creates states, if need be
diff --git a/src/analyses/dirty.h b/src/analyses/dirty.h
index e1d5b6aa64e..61ab0b0cb40 100644
--- a/src/analyses/dirty.h
+++ b/src/analyses/dirty.h
@@ -11,13 +11,15 @@ Date: March 2013
 #ifndef CPROVER_ANALYSES_DIRTY_H
 #define CPROVER_ANALYSES_DIRTY_H
 
+#include <unordered_set>
+
 #include <util/std_expr.h>
 #include <goto-programs/goto_functions.h>
 
 class dirtyt
 {
 public:
-  typedef hash_set_cont<irep_idt, irep_id_hash> id_sett;
+  typedef std::unordered_set<irep_idt, irep_id_hash> id_sett;
   typedef goto_functionst::goto_functiont goto_functiont;
 
   explicit dirtyt(const goto_functiont &goto_function)
diff --git a/src/analyses/flow_insensitive_analysis.cpp b/src/analyses/flow_insensitive_analysis.cpp
index e4782b76e73..77333faf4e8 100644
--- a/src/analyses/flow_insensitive_analysis.cpp
+++ b/src/analyses/flow_insensitive_analysis.cpp
@@ -309,7 +309,7 @@ bool flow_insensitive_analysis_baset::visit(
 
 //  {
 //    static unsigned state_cntr=0;
-//    std::string s("pastate"); s += i2string(state_cntr);
+//    std::string s("pastate"); s += std::to_string(state_cntr);
 //    std::ofstream f(s.c_str());
 //    goto_program.output_instruction(ns, "", f, l);
 //    f << std::endl;
diff --git a/src/analyses/flow_insensitive_analysis.h b/src/analyses/flow_insensitive_analysis.h
index 00c8ad4f798..3c64f5a0f63 100644
--- a/src/analyses/flow_insensitive_analysis.h
+++ b/src/analyses/flow_insensitive_analysis.h
@@ -13,6 +13,7 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <queue>
 #include <map>
 #include <iosfwd>
+#include <unordered_set>
 
 #include <goto-programs/goto_functions.h>
 
@@ -44,7 +45,7 @@ class flow_insensitive_abstract_domain_baset
   {
   }
 
-  typedef hash_set_cont<exprt, irep_hash> expr_sett;
+  typedef std::unordered_set<exprt, irep_hash> expr_sett;
 
   virtual void get_reference_set(
     const namespacet &ns,
diff --git a/src/analyses/goto_rw.h b/src/analyses/goto_rw.h
index 8aa1aa33f57..f4b289e9491 100644
--- a/src/analyses/goto_rw.h
+++ b/src/analyses/goto_rw.h
@@ -84,7 +84,7 @@ class rw_range_sett
   #ifdef USE_DSTRING
   typedef std::map<irep_idt, range_domain_baset*> objectst;
   #else
-  typedef hash_map_cont<irep_idt, range_domain_baset*, string_hash> objectst;
+  typedef std::unordered_map<irep_idt, range_domain_baset*, string_hash> objectst;
   #endif
 
   virtual ~rw_range_sett();
diff --git a/src/analyses/interval_domain.h b/src/analyses/interval_domain.h
index 9dd73b992f9..7f1059b63b2 100644
--- a/src/analyses/interval_domain.h
+++ b/src/analyses/interval_domain.h
@@ -11,9 +11,9 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <util/ieee_float.h>
 #include <util/mp_arith.h>
-#include <util/interval_template.h>
 
 #include "ai.h"
+#include "interval_template.h"
 
 typedef interval_template<mp_integer> integer_intervalt;
 typedef interval_template<ieee_floatt> ieee_float_intervalt;
diff --git a/src/util/interval_template.h b/src/analyses/interval_template.h
similarity index 98%
rename from src/util/interval_template.h
rename to src/analyses/interval_template.h
index 068edb83e5c..97ccf7a10d7 100644
--- a/src/util/interval_template.h
+++ b/src/analyses/interval_template.h
@@ -10,9 +10,9 @@ Author: Daniel Kroening, kroening@kroening.com
 #define CPROVER_UTIL_INTERVAL_TEMPLATE_H
 
 #include <algorithm>
-#include <ostream>
+#include <iosfwd>
 
-#include "threeval.h"
+#include <util/threeval.h>
 
 template<class T> class interval_template
 {
diff --git a/src/analyses/invariant_propagation.cpp b/src/analyses/invariant_propagation.cpp
index 56e285247e0..d73ad724eee 100644
--- a/src/analyses/invariant_propagation.cpp
+++ b/src/analyses/invariant_propagation.cpp
@@ -78,7 +78,7 @@ void invariant_propagationt::add_objects(
   goto_program.get_decl_identifiers(locals);
 
   // cache the list for the locals to speed things up
-  typedef hash_map_cont<irep_idt, object_listt, irep_id_hash> object_cachet;
+  typedef std::unordered_map<irep_idt, object_listt, irep_id_hash> object_cachet;
   object_cachet object_cache;
 
   for(goto_programt::instructionst::const_iterator
@@ -226,7 +226,7 @@ void invariant_propagationt::add_objects(
     const goto_programt &goto_program=f_it->second.body;
 
     // cache the list for the locals to speed things up
-    typedef hash_map_cont<irep_idt, object_listt, irep_id_hash> object_cachet;
+    typedef std::unordered_map<irep_idt, object_listt, irep_id_hash> object_cachet;
     object_cachet object_cache;
 
     for(goto_programt::instructionst::const_iterator
diff --git a/src/analyses/invariant_set.h b/src/analyses/invariant_set.h
index b24d0c75ab8..fc9ad07d59f 100644
--- a/src/analyses/invariant_set.h
+++ b/src/analyses/invariant_set.h
@@ -14,10 +14,11 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/union_find.h>
 #include <util/threeval.h>
 #include <util/mp_arith.h>
-#include <util/interval_template.h>
 
 #include <pointer-analysis/value_sets.h>
 
+#include "interval_template.h"
+
 class inv_object_storet
 {
 public:
diff --git a/src/analyses/reaching_definitions.h b/src/analyses/reaching_definitions.h
index 7b29b9e03db..90c91df8c5e 100644
--- a/src/analyses/reaching_definitions.h
+++ b/src/analyses/reaching_definitions.h
@@ -47,7 +47,7 @@ class sparse_bitvector_analysist
 protected:
   typedef typename std::map<V, std::size_t> inner_mapt;
   std::vector<typename inner_mapt::const_iterator> values;
-  hash_map_cont<irep_idt, inner_mapt, irep_id_hash> value_map;
+  std::unordered_map<irep_idt, inner_mapt, irep_id_hash> value_map;
 };
 
 struct reaching_definitiont
@@ -135,14 +135,14 @@ class rd_range_domaint:public ai_domain_baset
   #ifdef USE_DSTRING
   typedef std::map<irep_idt, values_innert> valuest;
   #else
-  typedef hash_map_cont<irep_idt, values_innert, irep_id_hash> valuest;
+  typedef std::unordered_map<irep_idt, values_innert, irep_id_hash> valuest;
   #endif
   valuest values;
 
   #ifdef USE_DSTRING
   typedef std::map<irep_idt, ranges_at_loct> export_cachet;
   #else
-  typedef hash_map_cont<irep_idt, ranges_at_loct, irep_id_hash>
+  typedef std::unordered_map<irep_idt, ranges_at_loct, irep_id_hash>
     export_cachet;
   #endif
   mutable export_cachet export_cache;
diff --git a/src/analyses/static_analysis.h b/src/analyses/static_analysis.h
index f25387d08f7..3e49425bbeb 100644
--- a/src/analyses/static_analysis.h
+++ b/src/analyses/static_analysis.h
@@ -15,6 +15,7 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <map>
 #include <iosfwd>
+#include <unordered_set>
 
 #include <goto-programs/goto_functions.h>
 
@@ -60,7 +61,7 @@ class domain_baset
   {
   }
 
-  typedef hash_set_cont<exprt, irep_hash> expr_sett;
+  typedef std::unordered_set<exprt, irep_hash> expr_sett;
 
   // will go away
   virtual void get_reference_set(
diff --git a/src/ansi-c/Makefile b/src/ansi-c/Makefile
index 5d6381c6b00..bed65d0d7b6 100644
--- a/src/ansi-c/Makefile
+++ b/src/ansi-c/Makefile
@@ -14,7 +14,7 @@ SRC = c_typecast.cpp ansi_c_y.tab.cpp ansi_c_lex.yy.cpp ansi_c_parser.cpp \
       literals/convert_float_literal.cpp \
       literals/convert_character_literal.cpp \
       literals/convert_integer_literal.cpp \
-      literals/convert_string_literal.cpp
+      literals/convert_string_literal.cpp c_misc.cpp
 
 INCLUDES= -I ..
 
diff --git a/src/ansi-c/ansi_c_entry_point.cpp b/src/ansi-c/ansi_c_entry_point.cpp
index 1acfb7d4459..de3b4bc675c 100644
--- a/src/ansi-c/ansi_c_entry_point.cpp
+++ b/src/ansi-c/ansi_c_entry_point.cpp
@@ -17,7 +17,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/config.h>
 #include <util/cprover_prefix.h>
 #include <util/prefix.h>
-#include <util/i2string.h>
 
 #include <ansi-c/c_types.h>
 #include <ansi-c/string_constant.h>
@@ -52,7 +51,7 @@ exprt::operandst build_function_environment(
   for(const auto & p : parameters)
   {
     irep_idt base_name=p.get_base_name();
-    if(base_name.empty()) base_name="argument#"+i2string(i);
+    if(base_name.empty()) base_name="argument#"+std::to_string(i);
     irep_idt identifier=id2string(goto_functionst::entry_point())+
       "::"+id2string(base_name);
 
diff --git a/src/ansi-c/ansi_c_internal_additions.cpp b/src/ansi-c/ansi_c_internal_additions.cpp
index ca4cf92f637..b41c436d0da 100644
--- a/src/ansi-c/ansi_c_internal_additions.cpp
+++ b/src/ansi-c/ansi_c_internal_additions.cpp
@@ -6,7 +6,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/config.h>
 
 #include "ansi_c_internal_additions.h"
@@ -94,7 +93,7 @@ static std::string architecture_string(int value, const char *s)
 {
   return std::string("const int __CPROVER_architecture_")+
          std::string(s)+
-         "="+i2string(value)+";\n";
+         "="+std::to_string(value)+";\n";
 }
 
 /*******************************************************************\
@@ -193,7 +192,7 @@ void ansi_c_internal_additions(std::string &code)
     "double __CPROVER_inf(void);\n"
     "float __CPROVER_inff(void);\n"
     "long double __CPROVER_infl(void);\n"
-    "int __CPROVER_thread_local __CPROVER_rounding_mode="+i2string(config.ansi_c.rounding_mode)+";\n"
+    "int __CPROVER_thread_local __CPROVER_rounding_mode="+std::to_string(config.ansi_c.rounding_mode)+";\n"
 
     // absolute value
     "int __CPROVER_abs(int x);\n"
diff --git a/src/ansi-c/ansi_c_parser.h b/src/ansi-c/ansi_c_parser.h
index 7e078abd7e5..2b35b56f34a 100644
--- a/src/ansi-c/ansi_c_parser.h
+++ b/src/ansi-c/ansi_c_parser.h
@@ -13,9 +13,7 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <util/parser.h>
 #include <util/expr.h>
-#include <util/hash_cont.h>
 #include <util/string_hash.h>
-#include <util/i2string.h>
 #include <util/mp_arith.h>
 #include <util/config.h>
 
diff --git a/src/ansi-c/ansi_c_scope.h b/src/ansi-c/ansi_c_scope.h
index c23f5eb2363..3e1d81e09f8 100644
--- a/src/ansi-c/ansi_c_scope.h
+++ b/src/ansi-c/ansi_c_scope.h
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_ANSI_C_ANSI_C_SCOPE_H
 #define CPROVER_ANSI_C_ANSI_C_SCOPE_H
 
-#include <util/hash_cont.h>
 #include <util/irep.h>
 
 typedef enum { ANSI_C_UNKNOWN, ANSI_C_SYMBOL, ANSI_C_TYPEDEF,
@@ -31,7 +30,7 @@ class ansi_c_scopet
 public:
   // This maps "scope names" (tag-X, label-X, X) to
   // ansi_c_identifiert.
-  typedef hash_map_cont<irep_idt, ansi_c_identifiert, irep_id_hash> name_mapt;
+  typedef std::unordered_map<irep_idt, ansi_c_identifiert, irep_id_hash> name_mapt;
   name_mapt name_map;
 
   std::string prefix;
diff --git a/src/util/c_misc.cpp b/src/ansi-c/c_misc.cpp
similarity index 94%
rename from src/util/c_misc.cpp
rename to src/ansi-c/c_misc.cpp
index 01fc2347dce..80d63e75717 100644
--- a/src/util/c_misc.cpp
+++ b/src/ansi-c/c_misc.cpp
@@ -28,7 +28,7 @@ Function: MetaChar
 
 \*******************************************************************/
 
-void MetaChar(std::string &out, char c, bool inString)
+static void MetaChar(std::string &out, char c, bool inString)
 {
   switch(c)
   {
@@ -101,6 +101,7 @@ void MetaChar(std::string &out, char c, bool inString)
   }
 }
 
+#if 0
 /*******************************************************************\
 
 Function: MetaChar
@@ -113,12 +114,13 @@ Function: MetaChar
 
 \*******************************************************************/
 
-std::string MetaChar(char c)
+static std::string MetaChar(char c)
 {
   std::string result;
   MetaChar(result, c, false);
   return result;
 }
+#endif
 
 /*******************************************************************\
 
diff --git a/src/util/c_misc.h b/src/ansi-c/c_misc.h
similarity index 92%
rename from src/util/c_misc.h
rename to src/ansi-c/c_misc.h
index b40f186db1f..a315a1efab2 100644
--- a/src/util/c_misc.h
+++ b/src/ansi-c/c_misc.h
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <string>
 
-std::string MetaChar(char c);
 std::string MetaString(const std::string &in);
 
 #endif // CPROVER_UTIL_C_MISC_H
diff --git a/src/ansi-c/c_preprocess.cpp b/src/ansi-c/c_preprocess.cpp
index 4f383e99828..00b82f1414d 100644
--- a/src/ansi-c/c_preprocess.cpp
+++ b/src/ansi-c/c_preprocess.cpp
@@ -22,7 +22,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <fstream>
 
 #include <util/config.h>
-#include <util/i2string.h>
 #include <util/message.h>
 #include <util/tempfile.h>
 #include <util/unicode.h>
@@ -769,7 +768,7 @@ bool c_preprocess_gcc_clang(
 
   command +=" -E -undef -D__CPROVER__";
 
-  command+=" -D__WORDSIZE="+i2string(config.ansi_c.pointer_width);
+  command+=" -D__WORDSIZE="+std::to_string(config.ansi_c.pointer_width);
 
   command+=" -D__DBL_MIN_EXP__=\"(-1021)\"";
   command+=" -D__FLT_MIN__=1.17549435e-38F";
@@ -1087,9 +1086,9 @@ bool c_preprocess_arm(
 
   command="armcc -E -D__CPROVER__";
 
-//  command+=" -D__sizeof_int="+i2string(config.ansi_c.int_width/8);
-//  command+=" -D__sizeof_long="+i2string(config.ansi_c.long_int_width/8);
-//  command+=" -D__sizeof_ptr="+i2string(config.ansi_c.pointer_width/8);
+//  command+=" -D__sizeof_int="+std::to_string(config.ansi_c.int_width/8);
+//  command+=" -D__sizeof_long="+std::to_string(config.ansi_c.long_int_width/8);
+//  command+=" -D__sizeof_ptr="+std::to_string(config.ansi_c.pointer_width/8);
   //command+=" -D__EDG_VERSION__=308";
   //command+=" -D__EDG__";
 //  command+=" -D__CC_ARM=1";
@@ -1104,7 +1103,7 @@ bool c_preprocess_arm(
 
   if(config.ansi_c.os!=configt::ansi_ct::ost::OS_WIN)
   {
-    command+=" -D__WORDSIZE="+i2string(config.ansi_c.pointer_width);
+    command+=" -D__WORDSIZE="+std::to_string(config.ansi_c.pointer_width);
 
     if(config.ansi_c.int_width==16)
       command+=GCC_DEFINES_16;
diff --git a/src/ansi-c/c_typecheck_base.cpp b/src/ansi-c/c_typecheck_base.cpp
index be7c58cc197..8d81099916e 100644
--- a/src/ansi-c/c_typecheck_base.cpp
+++ b/src/ansi-c/c_typecheck_base.cpp
@@ -10,7 +10,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/prefix.h>
 #include <util/config.h>
 #include <util/std_types.h>
-#include <util/i2string.h>
 
 #include "c_typecheck_base.h"
 #include "expr2c.h"
@@ -655,7 +654,7 @@ void c_typecheck_baset::typecheck_function_body(symbolt &symbol)
     // may be anonymous
     if(p_it->get_base_name()==irep_idt())
     {
-      irep_idt base_name="#anon"+i2string(anon_counter++);
+      irep_idt base_name="#anon"+std::to_string(anon_counter++);
       p_it->set_base_name(base_name);
     }
 
diff --git a/src/ansi-c/c_typecheck_base.h b/src/ansi-c/c_typecheck_base.h
index 9d79fe18429..6e3a566fd21 100644
--- a/src/ansi-c/c_typecheck_base.h
+++ b/src/ansi-c/c_typecheck_base.h
@@ -60,7 +60,7 @@ class c_typecheck_baset:
   const irep_idt mode;
   irep_idt current_symbol_id;
 
-  typedef hash_map_cont<irep_idt, typet, irep_id_hash> id_type_mapt;
+  typedef std::unordered_map<irep_idt, typet, irep_id_hash> id_type_mapt;
   id_type_mapt parameter_map;
 
   // overload to use language specific syntax
@@ -253,7 +253,7 @@ class c_typecheck_baset:
            src.id()==ID_c_bit_field;
   }
 
-  typedef hash_map_cont<irep_idt, irep_idt, irep_id_hash> asm_label_mapt;
+  typedef std::unordered_map<irep_idt, irep_idt, irep_id_hash> asm_label_mapt;
   asm_label_mapt asm_label_map;
 
   void apply_asm_label(const irep_idt &asm_label, symbolt &symbol);
diff --git a/src/ansi-c/c_typecheck_expr.cpp b/src/ansi-c/c_typecheck_expr.cpp
index 94a861e7a7d..1748d5eba40 100644
--- a/src/ansi-c/c_typecheck_expr.cpp
+++ b/src/ansi-c/c_typecheck_expr.cpp
@@ -17,7 +17,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/simplify_expr.h>
 #include <util/base_type.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/pointer_offset_size.h>
 #include <util/pointer_predicates.h>
 
diff --git a/src/ansi-c/c_typecheck_type.cpp b/src/ansi-c/c_typecheck_type.cpp
index 3002bd5c7d5..dcfb2ea5ccf 100644
--- a/src/ansi-c/c_typecheck_type.cpp
+++ b/src/ansi-c/c_typecheck_type.cpp
@@ -6,11 +6,12 @@ Author: Daniel Kroening, kroening@kroening.com
 
 \*******************************************************************/
 
+#include <unordered_set>
+
 #include <util/config.h>
 #include <util/simplify_expr.h>
 #include <util/arith_tools.h>
 #include <util/std_types.h>
-#include <util/i2string.h>
 #include <util/expr_util.h>
 #include <util/pointer_offset_size.h>
 
@@ -566,7 +567,7 @@ void c_typecheck_baset::typecheck_array_type(array_typet &type)
 
       do
       {
-        suffix="$array_size"+i2string(count);
+        suffix="$array_size"+std::to_string(count);
         temp_identifier=id2string(base_symbol.name)+suffix;
         count++;
       }
@@ -909,14 +910,14 @@ void c_typecheck_baset::typecheck_compound_body(
   {
     if(it->get_name()!=irep_idt()) continue;
 
-    it->set_name("$anon"+i2string(anon_member_counter++));
+    it->set_name("$anon"+std::to_string(anon_member_counter++));
     it->set_anonymous(true);
   }
 
   // scan for duplicate members
 
   {
-    hash_set_cont<irep_idt, irep_id_hash> members;
+    std::unordered_set<irep_idt, irep_id_hash> members;
 
     for(struct_union_typet::componentst::iterator
         it=components.begin();
diff --git a/src/ansi-c/expr2c.cpp b/src/ansi-c/expr2c.cpp
index 78ced9c86a3..8c69d099364 100644
--- a/src/ansi-c/expr2c.cpp
+++ b/src/ansi-c/expr2c.cpp
@@ -20,21 +20,22 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <set>
 
 #include <util/arith_tools.h>
-#include <util/c_misc.h>
 #include <util/config.h>
 #include <util/std_types.h>
 #include <util/std_code.h>
-#include <util/i2string.h>
 #include <util/ieee_float.h>
 #include <util/fixedbv.h>
 #include <util/prefix.h>
 #include <util/lispirep.h>
 #include <util/lispexpr.h>
+#include <util/namespace.h>
 #include <util/symbol.h>
 #include <util/suffix.h>
 #include <util/find_symbols.h>
 #include <util/pointer_offset_size.h>
 
+#include "c_misc.h"
+#include "c_qualifiers.h"
 #include "expr2c.h"
 #include "c_types.h"
 #include "expr2c_class.h"
@@ -288,11 +289,11 @@ std::string expr2ct::convert_rec(
         return q+"long double"+d;
     }
     const std::size_t fraction_bits=to_fixedbv_type(src).get_fraction_bits();
-    return q+"__CPROVER_fixedbv["+i2string(width)+"]["+i2string(fraction_bits)+"]"+d;
+    return q+"__CPROVER_fixedbv["+std::to_string(width)+"]["+std::to_string(fraction_bits)+"]"+d;
   }
   else if(src.id()==ID_c_bit_field)
   {
-    std::string width=i2string(to_c_bit_field_type(src).get_width());
+    std::string width=std::to_string(to_c_bit_field_type(src).get_width());
     return q+convert(src.subtype())+d+" : "+width;
   }
   else if(src.id()==ID_signedbv ||
@@ -1894,7 +1895,7 @@ std::string expr2ct::convert_symbol(
     dest=src.op0().get_string(ID_identifier);
   else
   {
-    hash_map_cont<irep_idt, irep_idt, irep_id_hash>::const_iterator
+    std::unordered_map<irep_idt, irep_idt, irep_id_hash>::const_iterator
       entry=shorthands.find(id);
     // we might be called from conversion of a type
     if(entry==shorthands.end())
diff --git a/src/ansi-c/expr2c_class.h b/src/ansi-c/expr2c_class.h
index 4048cf0f9ae..836837e7846 100644
--- a/src/ansi-c/expr2c_class.h
+++ b/src/ansi-c/expr2c_class.h
@@ -10,13 +10,14 @@ Author: Daniel Kroening, kroening@kroening.com
 #define CPROVER_ANSI_C_EXPR2C_CLASS_H
 
 #include <string>
+#include <unordered_map>
+#include <unordered_set>
 
-#include <util/expr.h>
 #include <util/std_code.h>
 #include <util/std_expr.h>
-#include <util/namespace.h>
 
-#include "c_qualifiers.h"
+class c_qualifierst;
+class namespacet;
 
 class expr2ct
 {
@@ -39,10 +40,10 @@ class expr2ct
 
   static std::string indent_str(unsigned indent);
 
-  hash_map_cont<irep_idt,
-                hash_set_cont<irep_idt, irep_id_hash>,
+  std::unordered_map<irep_idt,
+                std::unordered_set<irep_idt, irep_id_hash>,
                 irep_id_hash> ns_collision;
-  hash_map_cont<irep_idt, irep_idt, irep_id_hash> shorthands;
+  std::unordered_map<irep_idt, irep_idt, irep_id_hash> shorthands;
 
   unsigned sizeof_nesting;
 
diff --git a/src/ansi-c/literals/convert_character_literal.cpp b/src/ansi-c/literals/convert_character_literal.cpp
index 51e7b9b6fdc..f76af2eefa6 100644
--- a/src/ansi-c/literals/convert_character_literal.cpp
+++ b/src/ansi-c/literals/convert_character_literal.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <cassert>
 
 #include <util/arith_tools.h>
-#include <util/i2string.h>
 #include <util/std_expr.h>
 
 #include "../c_types.h"
@@ -71,7 +70,7 @@ exprt convert_character_literal(
       result=from_integer(x, type);
     }
     else
-      throw "wide literals with "+i2string(value.size())+
+      throw "wide literals with "+std::to_string(value.size())+
             " characters are not supported";
   }
   else
@@ -104,7 +103,7 @@ exprt convert_character_literal(
       result=from_integer(x, signed_int_type());
     }
     else
-      throw "literals with "+i2string(value.size())+
+      throw "literals with "+std::to_string(value.size())+
             " characters are not supported";
   }
 
diff --git a/src/ansi-c/literals/convert_float_literal.cpp b/src/ansi-c/literals/convert_float_literal.cpp
index c7a66c60f04..a7e256bf869 100644
--- a/src/ansi-c/literals/convert_float_literal.cpp
+++ b/src/ansi-c/literals/convert_float_literal.cpp
@@ -91,7 +91,7 @@ exprt convert_float_literal(const std::string &src)
     if(integer_bits==irep_idt())
       fraction_bits=width/2; // default
     else
-      fraction_bits=width-safe_string2int(id2string(integer_bits));
+      fraction_bits=width-std::stoi(id2string(integer_bits));
 
     mp_integer factor=mp_integer(1)<<fraction_bits;
     mp_integer value=significand*factor;
diff --git a/src/ansi-c/literals/convert_integer_literal.cpp b/src/ansi-c/literals/convert_integer_literal.cpp
index 10d149c8291..81fa0da5ac3 100644
--- a/src/ansi-c/literals/convert_integer_literal.cpp
+++ b/src/ansi-c/literals/convert_integer_literal.cpp
@@ -51,7 +51,7 @@ exprt convert_integer_literal(const std::string &src)
       // and "10i" (imaginary) for GCC.
       // If it's followed by a number, we do MS mode.
       if((i+1)<src.size() && isdigit(src[i+1]))
-        width_suffix=unsafe_c_str2int(src.c_str()+i+1);
+        width_suffix=unsafe_string2int(src.substr(i+1));
       else
         is_imaginary=true;
     }
diff --git a/src/ansi-c/padding.cpp b/src/ansi-c/padding.cpp
index 2326c297670..e02f2983973 100644
--- a/src/ansi-c/padding.cpp
+++ b/src/ansi-c/padding.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <algorithm>
 
 #include <util/config.h>
-#include <util/i2string.h>
 #include <util/pointer_offset_size.h>
 #include <util/simplify_expr.h>
 #include <util/arith_tools.h>
@@ -160,7 +159,7 @@ void add_padding(struct_typet &type, const namespacet &ns)
 
           struct_typet::componentt component;
           component.type()=padding_type;
-          component.set_name("$bit_field_pad"+i2string(padding_counter++));
+          component.set_name("$bit_field_pad"+std::to_string(padding_counter++));
           component.set_is_padding(true);
 
           it=components.insert(it, component);
@@ -181,7 +180,7 @@ void add_padding(struct_typet &type, const namespacet &ns)
 
       struct_typet::componentt component;
       component.type()=padding_type;
-      component.set_name("$bit_field_pad"+i2string(padding_counter++));
+      component.set_name("$bit_field_pad"+std::to_string(padding_counter++));
       component.set_is_padding(true);
 
       components.push_back(component);
@@ -256,7 +255,7 @@ void add_padding(struct_typet &type, const namespacet &ns)
 
         struct_typet::componentt component;
         component.type()=padding_type;
-        component.set_name("$pad"+i2string(padding_counter++));
+        component.set_name("$pad"+std::to_string(padding_counter++));
         component.set_is_padding(true);
 
         it=components.insert(it, component);
@@ -314,7 +313,7 @@ void add_padding(struct_typet &type, const namespacet &ns)
       // we insert after any final 'flexible member'
       struct_typet::componentt component;
       component.type()=padding_type;
-      component.set_name("$pad"+i2string(padding_counter++));
+      component.set_name("$pad"+std::to_string(padding_counter++));
       component.set_is_padding(true);
 
       components.push_back(component);
diff --git a/src/ansi-c/parser.y b/src/ansi-c/parser.y
index f23bff63918..c4335525180 100644
--- a/src/ansi-c/parser.y
+++ b/src/ansi-c/parser.y
@@ -2206,7 +2206,7 @@ compound_scope:
         /* nothing */
         {
           unsigned prefix=++PARSER.current_scope().compound_counter;
-          PARSER.new_scope(i2string(prefix)+"::");
+          PARSER.new_scope(std::to_string(prefix)+"::");
         }
         ;
 
@@ -2302,7 +2302,7 @@ iteration_statement:
             if(PARSER.for_has_scope)
             {
               unsigned prefix=++PARSER.current_scope().compound_counter;
-              PARSER.new_scope(i2string(prefix)+"::");
+              PARSER.new_scope(std::to_string(prefix)+"::");
             }
           }
           '(' declaration_or_expression_statement
diff --git a/src/ansi-c/parser_static.inc b/src/ansi-c/parser_static.inc
index 7e0936727a4..08a81c93e0d 100644
--- a/src/ansi-c/parser_static.inc
+++ b/src/ansi-c/parser_static.inc
@@ -2,7 +2,6 @@
 #include <util/std_types.h>
 #include <util/std_expr.h>
 #include <util/expr_util.h>
-#include <util/i2string.h>
 #include <util/string2int.h>
 
 #include "c_types.h"
diff --git a/src/ansi-c/type2name.cpp b/src/ansi-c/type2name.cpp
index f34ee45d29f..8087f6a6845 100644
--- a/src/ansi-c/type2name.cpp
+++ b/src/ansi-c/type2name.cpp
@@ -6,7 +6,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/std_types.h>
 #include <util/arith_tools.h>
 #include <util/namespace.h>
@@ -15,7 +14,7 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 #include "type2name.h"
 
-typedef hash_map_cont<irep_idt, std::pair<size_t, bool>, irep_id_hash>
+typedef std::unordered_map<irep_idt, std::pair<size_t, bool>, irep_id_hash>
   symbol_numbert;
 
 static std::string type2name(
@@ -64,7 +63,7 @@ static std::string type2name_symbol(
   // new entry, add definition
   if(entry.second)
   {
-    result="SYM#"+i2string(entry.first->second.first);
+    result="SYM#"+std::to_string(entry.first->second.first);
     result+="={";
     result+=type2name(symbol->type, ns, symbol_number);
     result+='}';
@@ -74,7 +73,7 @@ static std::string type2name_symbol(
 #if 0
   // in recursion, print the shorthand only
   else if(entry.first->second.second)
-    result="SYM#"+i2string(entry.first->second.first);
+    result="SYM#"+std::to_string(entry.first->second.first);
   // entering recursion
   else
   {
@@ -85,7 +84,7 @@ static std::string type2name_symbol(
 #else
   // shorthand only as structs/unions are always symbols
   else
-    result="SYM#"+i2string(entry.first->second.first);
+    result="SYM#"+std::to_string(entry.first->second.first);
 #endif
 
   return result;
diff --git a/src/cbmc/all_properties.cpp b/src/cbmc/all_properties.cpp
index 290c2f14a18..9ef6cb53dfa 100644
--- a/src/cbmc/all_properties.cpp
+++ b/src/cbmc/all_properties.cpp
@@ -108,7 +108,7 @@ safety_checkert::resultt bmc_all_propertiest::operator()()
         // this is likely an unwinding assertion
         property_id=id2string(
           it->source.pc->source_location.get_function())+".unwind."+
-          i2string(it->source.pc->loop_number);
+          std::to_string(it->source.pc->loop_number);
         goal_map[property_id].description=it->comment;
       }
       else
diff --git a/src/cbmc/bmc.cpp b/src/cbmc/bmc.cpp
index ba970e659c8..c0741fb700a 100644
--- a/src/cbmc/bmc.cpp
+++ b/src/cbmc/bmc.cpp
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <memory>
 
 #include <util/string2int.h>
-#include <util/i2string.h>
 #include <util/source_location.h>
 #include <util/time_stopping.h>
 #include <util/message.h>
@@ -328,7 +327,7 @@ void bmct::show_program()
       if(!step.guard.is_true())
       {
         languages.from_expr(step.guard, string_value);
-        std::cout << std::string(i2string(count).size()+3, ' ');
+        std::cout << std::string(std::to_string(count).size()+3, ' ');
         std::cout << "guard: " << string_value << "\n";
       }
 
@@ -344,7 +343,7 @@ void bmct::show_program()
       if(!step.guard.is_true())
       {
         languages.from_expr(step.guard, string_value);
-        std::cout << std::string(i2string(count).size()+3, ' ');
+        std::cout << std::string(std::to_string(count).size()+3, ' ');
         std::cout << "guard: " << string_value << "\n";
       }
 
@@ -360,7 +359,7 @@ void bmct::show_program()
       if(!step.guard.is_true())
       {
         languages.from_expr(step.guard, string_value);
-        std::cout << std::string(i2string(count).size()+3, ' ');
+        std::cout << std::string(std::to_string(count).size()+3, ' ');
         std::cout << "guard: " << string_value << "\n";
       }
 
@@ -385,7 +384,7 @@ void bmct::show_program()
       if(!step.guard.is_true())
       {
         languages.from_expr(step.guard, string_value);
-        std::cout << std::string(i2string(count).size()+3, ' ');
+        std::cout << std::string(std::to_string(count).size()+3, ' ');
         std::cout << "guard: " << string_value << "\n";
       }
 
diff --git a/src/cbmc/bmc.h b/src/cbmc/bmc.h
index a99d859b19d..8206a7ec876 100644
--- a/src/cbmc/bmc.h
+++ b/src/cbmc/bmc.h
@@ -12,7 +12,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <list>
 #include <map>
 
-#include <util/hash_cont.h>
 #include <util/options.h>
 
 #include <solvers/prop/prop.h>
diff --git a/src/cbmc/bmc_cover.cpp b/src/cbmc/bmc_cover.cpp
index 72e45362437..df33aac8673 100644
--- a/src/cbmc/bmc_cover.cpp
+++ b/src/cbmc/bmc_cover.cpp
@@ -403,8 +403,8 @@ bool bmc_covert::operator()()
         if(goal.source_location.is_not_nil())
           result["sourceLocation"]=json(goal.source_location);
       }
-      json_result["totalGoals"]=json_numbert(i2string(goal_map.size()));
-      json_result["goalsCovered"]=json_numbert(i2string(goals_covered));
+      json_result["totalGoals"]=json_numbert(std::to_string(goal_map.size()));
+      json_result["goalsCovered"]=json_numbert(std::to_string(goals_covered));
 
       json_arrayt &tests_array=json_result["tests"].make_array();
       for(const auto & test : tests)
diff --git a/src/cbmc/cbmc_parse_options.cpp b/src/cbmc/cbmc_parse_options.cpp
index 08955180271..3514e908c04 100644
--- a/src/cbmc/cbmc_parse_options.cpp
+++ b/src/cbmc/cbmc_parse_options.cpp
@@ -17,7 +17,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/language.h>
 #include <util/unicode.h>
 #include <util/memory_info.h>
-#include <util/i2string.h>
 
 #include <ansi-c/c_preprocess.h>
 
diff --git a/src/cbmc/cbmc_solvers.h b/src/cbmc/cbmc_solvers.h
index c834b4875d0..35ded2a5c92 100644
--- a/src/cbmc/cbmc_solvers.h
+++ b/src/cbmc/cbmc_solvers.h
@@ -13,7 +13,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <map>
 #include <memory>
 
-#include <util/hash_cont.h>
 #include <util/options.h>
 
 #include <solvers/prop/prop.h>
diff --git a/src/cbmc/symex_bmc.cpp b/src/cbmc/symex_bmc.cpp
index b4ae665079e..d97e241360e 100644
--- a/src/cbmc/symex_bmc.cpp
+++ b/src/cbmc/symex_bmc.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <limits>
 
 #include <util/source_location.h>
-#include <util/i2string.h>
 
 #include "symex_bmc.h"
 
diff --git a/src/cbmc/symex_bmc.h b/src/cbmc/symex_bmc.h
index 76026b3757f..07ce88834ed 100644
--- a/src/cbmc/symex_bmc.h
+++ b/src/cbmc/symex_bmc.h
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_CBMC_SYMEX_BMC_H
 #define CPROVER_CBMC_SYMEX_BMC_H
 
-#include <util/hash_cont.h>
 #include <util/message.h>
 
 #include <goto-symex/goto_symex.h>
@@ -60,7 +59,7 @@ class symex_bmct:
   unsigned max_unwind;
   bool max_unwind_is_set;
 
-  typedef hash_map_cont<irep_idt, unsigned, irep_id_hash> loop_limitst;
+  typedef std::unordered_map<irep_idt, unsigned, irep_id_hash> loop_limitst;
   loop_limitst loop_limits;
 
   typedef std::map<unsigned, loop_limitst> thread_loop_limitst;
@@ -85,7 +84,7 @@ class symex_bmct:
 
   virtual void no_body(const irep_idt &identifier);
 
-  hash_set_cont<irep_idt, irep_id_hash> body_warnings;
+  std::unordered_set<irep_idt, irep_id_hash> body_warnings;
 };
 
 #endif // CPROVER_CBMC_SYMEX_BMC_H
diff --git a/src/cegis/control/value/float_helper.cpp b/src/cegis/control/value/float_helper.cpp
index 712f6b226dd..4f8fb9dce9c 100644
--- a/src/cegis/control/value/float_helper.cpp
+++ b/src/cegis/control/value/float_helper.cpp
@@ -2,9 +2,9 @@
 
 #include <util/fixedbv.h>
 #include <util/ieee_float.h>
+#include <util/namespace.h>
 #include <util/std_expr.h>
 #include <util/symbol_table.h>
-#include <util/namespace_utils.h>
 
 #include <cegis/control/value/control_types.h>
 
diff --git a/src/cegis/instrument/meta_variables.cpp b/src/cegis/instrument/meta_variables.cpp
index 437bafec83e..41e163d425f 100644
--- a/src/cegis/instrument/meta_variables.cpp
+++ b/src/cegis/instrument/meta_variables.cpp
@@ -1,5 +1,3 @@
-#include <util/namespace_utils.h>
-
 #include <ansi-c/c_types.h>
 
 #include <goto-programs/goto_functions.h>
diff --git a/src/cegis/invariant/constant/literals_constant_strategy.cpp b/src/cegis/invariant/constant/literals_constant_strategy.cpp
index 2259473be02..ec12572494b 100644
--- a/src/cegis/invariant/constant/literals_constant_strategy.cpp
+++ b/src/cegis/invariant/constant/literals_constant_strategy.cpp
@@ -2,7 +2,6 @@
 
 #include <util/arith_tools.h>
 #include <util/bv_arithmetic.h>
-#include <util/namespace_utils.h>
 
 #include <cegis/cegis-util/constant_width.h>
 #include <cegis/instrument/meta_variables.h>
diff --git a/src/cegis/invariant/symex/learn/replace_operators.cpp b/src/cegis/invariant/symex/learn/replace_operators.cpp
index b7c2dc2bdf0..e46db87a394 100644
--- a/src/cegis/invariant/symex/learn/replace_operators.cpp
+++ b/src/cegis/invariant/symex/learn/replace_operators.cpp
@@ -1,4 +1,4 @@
-#include <util/namespace_utils.h>
+#include <util/type_eq.h>
 
 #include <cegis/instrument/meta_variables.h>
 #include <cegis/invariant/symex/learn/replace_operators.h>
diff --git a/src/cpp/cpp_parser.h b/src/cpp/cpp_parser.h
index 6251c377f96..f2db8e6c2f7 100644
--- a/src/cpp/cpp_parser.h
+++ b/src/cpp/cpp_parser.h
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 #include <cassert>
 
-#include <util/hash_cont.h>
 #include <util/string_hash.h>
 #include <util/parser.h>
 #include <util/expr.h>
diff --git a/src/cpp/cpp_scopes.cpp b/src/cpp/cpp_scopes.cpp
index 2fa0dcc17a8..d3274b50f43 100644
--- a/src/cpp/cpp_scopes.cpp
+++ b/src/cpp/cpp_scopes.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 #include <ostream>
 
-#include <util/i2string.h>
 
 #include "cpp_scopes.h"
 
@@ -27,7 +26,7 @@ Function: cpp_scopest::new_block_scope
 cpp_scopet &cpp_scopest::new_block_scope()
 {
   unsigned prefix=++current_scope().compound_counter;
-  return new_scope(i2string(prefix), cpp_idt::BLOCK_SCOPE);
+  return new_scope(std::to_string(prefix), cpp_idt::BLOCK_SCOPE);
 }
 
 /*******************************************************************\
diff --git a/src/cpp/cpp_scopes.h b/src/cpp/cpp_scopes.h
index 8ab73a98d15..0c2e0420383 100644
--- a/src/cpp/cpp_scopes.h
+++ b/src/cpp/cpp_scopes.h
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 #include <set>
 
-#include <util/hash_cont.h>
 #include <util/symbol.h>
 #include <util/string_hash.h>
 
@@ -63,7 +62,7 @@ class cpp_scopest
   }
 
   // mapping from function/class/scope names to their cpp_idt
-  typedef hash_map_cont<irep_idt, cpp_idt *, irep_id_hash> id_mapt;
+  typedef std::unordered_map<irep_idt, cpp_idt *, irep_id_hash> id_mapt;
   id_mapt id_map;
 
   cpp_scopet *current_scope_ptr;
diff --git a/src/cpp/cpp_type2name.cpp b/src/cpp/cpp_type2name.cpp
index 95c33c778ff..ac745f89ffb 100644
--- a/src/cpp/cpp_type2name.cpp
+++ b/src/cpp/cpp_type2name.cpp
@@ -10,7 +10,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 #include <util/type.h>
 #include <util/std_types.h>
-#include <util/i2string.h>
 
 /*******************************************************************\
 
@@ -28,7 +27,7 @@ static std::string do_prefix(const std::string &s)
 {
   if(s.find(',')!=std::string::npos ||
      (s!="" && isdigit(s[0])))
-    return i2string(s.size())+"_"+s;
+    return std::to_string(s.size())+"_"+s;
 
   return s;
 }
diff --git a/src/cpp/cpp_typecheck.cpp b/src/cpp/cpp_typecheck.cpp
index 09706ac4795..951a72e758d 100644
--- a/src/cpp/cpp_typecheck.cpp
+++ b/src/cpp/cpp_typecheck.cpp
@@ -10,7 +10,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 #include <util/expr_util.h>
 #include <util/arith_tools.h>
-#include <util/i2string.h>
 #include <util/source_location.h>
 #include <util/symbol.h>
 
diff --git a/src/cpp/cpp_typecheck_code.cpp b/src/cpp/cpp_typecheck_code.cpp
index c6f97931455..50822b74788 100644
--- a/src/cpp/cpp_typecheck_code.cpp
+++ b/src/cpp/cpp_typecheck_code.cpp
@@ -6,7 +6,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/expr_util.h>
 #include <util/source_location.h>
 
diff --git a/src/cpp/cpp_typecheck_compound_type.cpp b/src/cpp/cpp_typecheck_compound_type.cpp
index 502a0ba3517..e60bd707691 100644
--- a/src/cpp/cpp_typecheck_compound_type.cpp
+++ b/src/cpp/cpp_typecheck_compound_type.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 #include <algorithm>
 
-#include <util/i2string.h>
 #include <util/arith_tools.h>
 #include <util/expr_util.h>
 #include <util/simplify_expr.h>
@@ -162,7 +161,7 @@ void cpp_typecheckt::typecheck_compound_type(
     // most of these should be named by now; see
     // cpp_declarationt::name_anon_struct_union()
 
-    base_name=std::string("#anon_")+i2string(++anon_counter);
+    base_name=std::string("#anon_")+std::to_string(++anon_counter);
     type.set(ID_C_is_anonymous, true);
     dest_scope=&cpp_scopes.current_scope();
   }
@@ -654,7 +653,7 @@ void cpp_typecheckt::typecheck_compound_declarator(
           irep_idt base_name = arg.get_base_name();
 
           if(base_name==irep_idt())
-            base_name="arg"+i2string(i);
+            base_name="arg"+std::to_string(i);
 
           symbolt arg_symb;
           arg_symb.name = id2string(func_symb.name) + "::"+ id2string(base_name);
@@ -1582,7 +1581,7 @@ void cpp_typecheckt::convert_anon_struct_union_member(
   }
 
   // produce an anonymous member
-  irep_idt base_name="#anon_member"+i2string(components.size());
+  irep_idt base_name="#anon_member"+std::to_string(components.size());
 
   irep_idt identifier=
     cpp_scopes.current_scope().prefix+
diff --git a/src/cpp/cpp_typecheck_declaration.cpp b/src/cpp/cpp_typecheck_declaration.cpp
index 1d7fec47c9f..6771d58aa6c 100644
--- a/src/cpp/cpp_typecheck_declaration.cpp
+++ b/src/cpp/cpp_typecheck_declaration.cpp
@@ -6,7 +6,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 \********************************************************************/
 
-#include <util/i2string.h>
 #include <util/expr_util.h>
 
 #include "cpp_typecheck.h"
@@ -66,7 +65,7 @@ void cpp_typecheckt::convert_anonymous_union(
   new_code.reserve_operands(declaration.declarators().size());
 
   // unnamed object
-  std::string identifier="#anon_union"+i2string(anon_counter++);
+  std::string identifier="#anon_union"+std::to_string(anon_counter++);
 
   irept name(ID_name);
   name.set(ID_identifier, identifier);
diff --git a/src/cpp/cpp_typecheck_enum_type.cpp b/src/cpp/cpp_typecheck_enum_type.cpp
index abff4131755..1813ee060d0 100644
--- a/src/cpp/cpp_typecheck_enum_type.cpp
+++ b/src/cpp/cpp_typecheck_enum_type.cpp
@@ -6,7 +6,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/arith_tools.h>
 
 #include <ansi-c/c_qualifiers.h>
diff --git a/src/cpp/cpp_typecheck_expr.cpp b/src/cpp/cpp_typecheck_expr.cpp
index d057883067d..8e98bf1a937 100644
--- a/src/cpp/cpp_typecheck_expr.cpp
+++ b/src/cpp/cpp_typecheck_expr.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 #include <cstdlib>
 
 #include <util/expr_util.h>
-#include <util/i2string.h>
 #include <util/std_types.h>
 #include <util/arith_tools.h>
 #include <util/std_expr.h>
diff --git a/src/cpp/cpp_typecheck_function.cpp b/src/cpp/cpp_typecheck_function.cpp
index 5b3b1c1c917..e0e1c5bf822 100644
--- a/src/cpp/cpp_typecheck_function.cpp
+++ b/src/cpp/cpp_typecheck_function.cpp
@@ -6,8 +6,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 \*******************************************************************/
 
-#include <util/i2string.h>
-#include <util/identifier.h>
 #include <util/expr_util.h>
 
 #include <ansi-c/c_qualifiers.h>
@@ -37,7 +35,7 @@ void cpp_typecheckt::convert_parameter(
 
   if(base_name.empty())
   {
-    base_name="#anon_arg"+i2string(anon_counter++);
+    base_name="#anon_arg"+std::to_string(anon_counter++);
     parameter.set_base_name(base_name);
   }
 
diff --git a/src/cpp/cpp_typecheck_method_bodies.cpp b/src/cpp/cpp_typecheck_method_bodies.cpp
index 5635cf5005e..86e35e9f4d4 100644
--- a/src/cpp/cpp_typecheck_method_bodies.cpp
+++ b/src/cpp/cpp_typecheck_method_bodies.cpp
@@ -6,7 +6,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 
 #include "cpp_typecheck.h"
 
diff --git a/src/cpp/cpp_typecheck_resolve.cpp b/src/cpp/cpp_typecheck_resolve.cpp
index 81867bac864..3974920870c 100644
--- a/src/cpp/cpp_typecheck_resolve.cpp
+++ b/src/cpp/cpp_typecheck_resolve.cpp
@@ -12,7 +12,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 #include <util/expr_util.h>
 #include <util/std_types.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/arith_tools.h>
 #include <util/prefix.h>
 
diff --git a/src/cpp/cpp_typecheck_template.cpp b/src/cpp/cpp_typecheck_template.cpp
index e2ef50d8fee..73997bb5aff 100644
--- a/src/cpp/cpp_typecheck_template.cpp
+++ b/src/cpp/cpp_typecheck_template.cpp
@@ -7,7 +7,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 \*******************************************************************/
 
 #include <util/expr_util.h>
-#include <util/i2string.h>
 #include <util/simplify_expr.h>
 
 #include "cpp_type2name.h"
@@ -525,9 +524,9 @@ std::string cpp_typecheckt::class_template_identifier(
     if(counter!=0) identifier+=',';
 
     if(it->id()==ID_type)
-      identifier+="Type"+i2string(counter);
+      identifier+="Type"+std::to_string(counter);
     else
-      identifier+="Non_Type"+i2string(counter);
+      identifier+="Non_Type"+std::to_string(counter);
 
     counter++;
   }
@@ -855,7 +854,7 @@ cpp_scopet &cpp_typecheckt::typecheck_template_parameters(
 
   assert(type.id()==ID_template);
 
-  std::string id_suffix="template::"+i2string(template_counter++);
+  std::string id_suffix="template::"+std::to_string(template_counter++);
 
   // produce a new scope for the template parameters
   cpp_scopet &template_scope=
@@ -894,7 +893,7 @@ cpp_scopet &cpp_typecheckt::typecheck_template_parameters(
     if(declarator.name().is_nil())
     {
       irept name(ID_name);
-      name.set(ID_identifier, "anon#"+i2string(++anon_count));
+      name.set(ID_identifier, "anon#"+std::to_string(++anon_count));
       declarator.name()=cpp_namet();
       declarator.name().get_sub().push_back(name);
     }
diff --git a/src/cpp/expr2cpp.cpp b/src/cpp/expr2cpp.cpp
index 38779ec8581..1ed05750739 100644
--- a/src/cpp/expr2cpp.cpp
+++ b/src/cpp/expr2cpp.cpp
@@ -11,11 +11,12 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 #include <util/std_types.h>
 #include <util/std_expr.h>
 #include <util/symbol.h>
-#include <util/hash_cont.h>
-#include <util/c_misc.h>
 #include <util/lispirep.h>
 #include <util/lispexpr.h>
+#include <util/namespace.h>
 
+#include <ansi-c/c_misc.h>
+#include <ansi-c/c_qualifiers.h>
 #include <ansi-c/expr2c_class.h>
 
 #include "expr2cpp.h"
@@ -51,7 +52,7 @@ class expr2cppt:public expr2ct
     const c_qualifierst &qualifiers,
     const std::string &declarator);
 
-  typedef hash_set_cont<std::string, string_hash> id_sett;
+  typedef std::unordered_set<std::string, string_hash> id_sett;
 };
 
 /*******************************************************************\
diff --git a/src/cpp/parse.cpp b/src/cpp/parse.cpp
index e0d1ee023ba..e07b21c55bf 100644
--- a/src/cpp/parse.cpp
+++ b/src/cpp/parse.cpp
@@ -5,7 +5,6 @@
 #include <util/std_code.h>
 #include <util/std_expr.h>
 #include <util/std_types.h>
-#include <util/i2string.h>
 
 #include <ansi-c/ansi_c_y.tab.h>
 
@@ -114,7 +113,7 @@ class new_scopet
   irep_idt get_anon_id()
   {
     ++anon_count;
-    return "#anon"+i2string(anon_count);
+    return "#anon"+std::to_string(anon_count);
   }
 
   std::string full_name() const
@@ -536,7 +535,7 @@ bool Parser::SyntaxError()
   {
     source_locationt source_location;
     source_location.set_file(t[0].filename);
-    source_location.set_line(i2string(t[0].line_no));
+    source_location.set_line(std::to_string(t[0].line_no));
 
     std::string message="parse error before `";
 
diff --git a/src/goto-cc/xml_binaries/xml_irep_hashing.h b/src/goto-cc/xml_binaries/xml_irep_hashing.h
index d329bfceee0..5fe4df7bb20 100644
--- a/src/goto-cc/xml_binaries/xml_irep_hashing.h
+++ b/src/goto-cc/xml_binaries/xml_irep_hashing.h
@@ -13,7 +13,6 @@ Date: July 2006
 
 #include <util/xml.h>
 #include <util/irep.h>
-#include <util/hash_cont.h>
 
 class xml_irep_convertt {
   private:
@@ -50,9 +49,9 @@ class xml_irep_convertt {
   public:
     class ireps_containert {
       public:
-        typedef hash_map_cont<unsigned long, irept, ul_hash, ul_eq> id_containert;
+        typedef std::unordered_map<unsigned long, irept, ul_hash, ul_eq> id_containert;
         id_containert id_container;
-        typedef hash_map_cont<irept, unsigned long, irep_full_hash, irep_content_eq> content_containert;
+        typedef std::unordered_map<irept, unsigned long, irep_full_hash, irep_content_eq> content_containert;
         content_containert content_container;
         typedef std::map<unsigned, unsigned> id_replace_mapt;
         id_replace_mapt id_replace_map;
diff --git a/src/goto-diff/change_impact.cpp b/src/goto-diff/change_impact.cpp
index bd53f1f3727..a8ab174ee68 100644
--- a/src/goto-diff/change_impact.cpp
+++ b/src/goto-diff/change_impact.cpp
@@ -120,7 +120,7 @@ void full_slicert::operator()(
 #ifdef DEBUG_FULL_SLICERT
         else
         {
-          std::string c="ins:"+i2string(i_it->location_number);
+          std::string c="ins:"+std::to_string(i_it->location_number);
           c+=" req by:";
           for(std::set<unsigned>::const_iterator
               req_it=cfg[e].required_by.begin();
@@ -128,7 +128,7 @@ void full_slicert::operator()(
               ++req_it)
           {
             if(req_it!=cfg[e].required_by.begin()) c+=",";
-            c+=i2string(*req_it);
+            c+=std::to_string(*req_it);
           }
           i_it->source_location.set_column(c);  // for show-goto-functions
           i_it->source_location.set_comment(c); // for dump-c
diff --git a/src/goto-diff/goto_diff_base.cpp b/src/goto-diff/goto_diff_base.cpp
index a8f1ff4f9ea..248c161b8eb 100644
--- a/src/goto-diff/goto_diff_base.cpp
+++ b/src/goto-diff/goto_diff_base.cpp
@@ -6,7 +6,6 @@ Author: Peter Schrammel
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/json_expr.h>
 
 #include "goto_diff.h"
@@ -68,7 +67,7 @@ std::ostream &goto_difft::output_functions(std::ostream &out) const
     {
       json_objectt json_result;
       json_result["totalNumberOfFunctions"]=
-        json_stringt(i2string(total_functions_count));
+        json_stringt(std::to_string(total_functions_count));
       convert_function_group
         (json_result["newFunctions"].make_array(), new_functions);
       convert_function_group(
diff --git a/src/goto-diff/goto_diff_parse_options.cpp b/src/goto-diff/goto_diff_parse_options.cpp
index 1943c7c5ced..c819d1537d0 100644
--- a/src/goto-diff/goto_diff_parse_options.cpp
+++ b/src/goto-diff/goto_diff_parse_options.cpp
@@ -15,7 +15,6 @@ Author: Peter Schrammel
 #include <util/config.h>
 #include <util/expr_util.h>
 #include <util/language.h>
-#include <util/i2string.h>
 #include <util/options.h>
 
 #include <goto-programs/goto_convert_functions.h>
diff --git a/src/goto-instrument/accelerate/accelerate.h b/src/goto-instrument/accelerate/accelerate.h
index 4f2c10be9a9..e4ed3700e87 100644
--- a/src/goto-instrument/accelerate/accelerate.h
+++ b/src/goto-instrument/accelerate/accelerate.h
@@ -2,7 +2,6 @@
 #define CPROVER_GOTO_INSTRUMENT_ACCELERATE_ACCELERATE_H
 
 #include <util/namespace.h>
-#include <util/hash_cont.h>
 #include <util/expr.h>
 
 #include <analyses/natural_loops.h>
diff --git a/src/goto-instrument/accelerate/acceleration_utils.cpp b/src/goto-instrument/accelerate/acceleration_utils.cpp
index 384ff5db56e..7d3227984a0 100644
--- a/src/goto-instrument/accelerate/acceleration_utils.cpp
+++ b/src/goto-instrument/accelerate/acceleration_utils.cpp
@@ -22,7 +22,6 @@
 #include <util/options.h>
 #include <util/std_expr.h>
 #include <util/std_code.h>
-#include <util/i2string.h>
 #include <util/find_symbols.h>
 #include <util/rename.h>
 #include <util/simplify_expr.h>
@@ -1117,7 +1116,7 @@ symbolt acceleration_utilst::fresh_symbol(std::string base, typet type)
 {
   static int num_symbols = 0;
 
-  std::string name = base + "_" + i2string(num_symbols++);
+  std::string name = base + "_" + std::to_string(num_symbols++);
   symbolt ret;
   ret.module = "scratch";
   ret.name = name;
diff --git a/src/goto-instrument/accelerate/acceleration_utils.h b/src/goto-instrument/accelerate/acceleration_utils.h
index 3275a25c687..02aba5cb387 100644
--- a/src/goto-instrument/accelerate/acceleration_utils.h
+++ b/src/goto-instrument/accelerate/acceleration_utils.h
@@ -5,7 +5,6 @@
 #include <set>
 
 #include <util/symbol_table.h>
-#include <util/hash_cont.h>
 
 #include <goto-programs/goto_program.h>
 #include <goto-programs/goto_functions.h>
@@ -18,7 +17,7 @@
 #include "accelerator.h"
 #include "cone_of_influence.h"
 
-typedef hash_map_cont<exprt, exprt, irep_hash> expr_mapt;
+typedef std::unordered_map<exprt, exprt, irep_hash> expr_mapt;
 
 class acceleration_utilst {
  public:
diff --git a/src/goto-instrument/accelerate/cone_of_influence.h b/src/goto-instrument/accelerate/cone_of_influence.h
index cc8ebd1cdde..59512c1853a 100644
--- a/src/goto-instrument/accelerate/cone_of_influence.h
+++ b/src/goto-instrument/accelerate/cone_of_influence.h
@@ -5,10 +5,9 @@
 
 #include <util/std_expr.h>
 #include <util/ref_expr_set.h>
-#include <util/hash_cont.h>
 #include <util/symbol_table.h>
 
-typedef hash_set_cont<exprt, irep_hash> expr_sett;
+typedef std::unordered_set<exprt, irep_hash> expr_sett;
 
 void cone_of_influence(goto_programt &program,
     expr_sett &targets,
@@ -34,7 +33,7 @@ class cone_of_influencet {
       expr_sett &targets);
   void gather_rvalues(const exprt &expr, expr_sett &rvals);
 
-  typedef hash_map_cont<unsigned int, expr_sett> cone_mapt;
+  typedef std::unordered_map<unsigned int, expr_sett> cone_mapt;
   cone_mapt cone_map;
 
   const goto_programt &program;
diff --git a/src/goto-instrument/accelerate/disjunctive_polynomial_acceleration.cpp b/src/goto-instrument/accelerate/disjunctive_polynomial_acceleration.cpp
index c22ae123fc7..65c8056b4a1 100644
--- a/src/goto-instrument/accelerate/disjunctive_polynomial_acceleration.cpp
+++ b/src/goto-instrument/accelerate/disjunctive_polynomial_acceleration.cpp
@@ -22,7 +22,6 @@
 #include <util/options.h>
 #include <util/std_expr.h>
 #include <util/std_code.h>
-#include <util/i2string.h>
 #include <util/find_symbols.h>
 #include <util/rename.h>
 #include <util/simplify_expr.h>
diff --git a/src/goto-instrument/accelerate/polynomial_accelerator.cpp b/src/goto-instrument/accelerate/polynomial_accelerator.cpp
index a13eb34a9c4..f8badf492ed 100644
--- a/src/goto-instrument/accelerate/polynomial_accelerator.cpp
+++ b/src/goto-instrument/accelerate/polynomial_accelerator.cpp
@@ -18,7 +18,6 @@
 #include <util/options.h>
 #include <util/std_expr.h>
 #include <util/std_code.h>
-#include <util/i2string.h>
 #include <util/find_symbols.h>
 #include <util/rename.h>
 #include <util/simplify_expr.h>
diff --git a/src/goto-instrument/accelerate/sat_path_enumerator.cpp b/src/goto-instrument/accelerate/sat_path_enumerator.cpp
index 3ce3eaf1888..a46608f2a57 100644
--- a/src/goto-instrument/accelerate/sat_path_enumerator.cpp
+++ b/src/goto-instrument/accelerate/sat_path_enumerator.cpp
@@ -22,7 +22,6 @@
 #include <util/options.h>
 #include <util/std_expr.h>
 #include <util/std_code.h>
-#include <util/i2string.h>
 #include <util/find_symbols.h>
 #include <util/rename.h>
 #include <util/simplify_expr.h>
diff --git a/src/goto-instrument/accelerate/scratch_program.cpp b/src/goto-instrument/accelerate/scratch_program.cpp
index 8798b18c0e2..87d1b8bf3b8 100644
--- a/src/goto-instrument/accelerate/scratch_program.cpp
+++ b/src/goto-instrument/accelerate/scratch_program.cpp
@@ -1,4 +1,3 @@
-#include <util/i2string.h>
 #include <util/fixedbv.h>
 #include <util/decision_procedure.h>
 
diff --git a/src/goto-instrument/call_sequences.cpp b/src/goto-instrument/call_sequences.cpp
index c39119972af..67f4dae9598 100644
--- a/src/goto-instrument/call_sequences.cpp
+++ b/src/goto-instrument/call_sequences.cpp
@@ -10,6 +10,7 @@ Date: April 2013
 
 #include <stack>
 #include <iostream>
+#include <unordered_set>
 
 #include <util/std_expr.h>
 
@@ -212,7 +213,7 @@ class check_call_sequencet
     }
   };
 
-  typedef hash_set_cont<statet, state_hash> statest;
+  typedef std::unordered_set<statet, state_hash> statest;
   statest states;
 };
 
diff --git a/src/goto-instrument/code_contracts.cpp b/src/goto-instrument/code_contracts.cpp
index d05c7bdbcf8..2e66c11bf87 100644
--- a/src/goto-instrument/code_contracts.cpp
+++ b/src/goto-instrument/code_contracts.cpp
@@ -8,7 +8,6 @@ Date: February 2016
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/cprover_prefix.h>
 #include <util/replace_symbol.h>
 
@@ -41,7 +40,7 @@ class code_contractst
 
   unsigned temporary_counter;
 
-  typedef hash_set_cont<irep_idt, irep_id_hash> id_sett;
+  typedef std::unordered_set<irep_idt, irep_id_hash> id_sett;
   id_sett summarized;
 
   void code_contracts(goto_functionst::goto_functiont &goto_function);
@@ -297,7 +296,7 @@ const symbolt &code_contractst::new_tmp_symbol(
 
   do
   {
-    new_symbol.base_name="tmp_cc$"+i2string(++temporary_counter);
+    new_symbol.base_name="tmp_cc$"+std::to_string(++temporary_counter);
     new_symbol.name=new_symbol.base_name;
   } while(symbol_table.move(new_symbol, symbol_ptr));
 
diff --git a/src/goto-instrument/count_eloc.cpp b/src/goto-instrument/count_eloc.cpp
index 5a92186fda7..2988b8637d2 100644
--- a/src/goto-instrument/count_eloc.cpp
+++ b/src/goto-instrument/count_eloc.cpp
@@ -9,15 +9,16 @@ Date: December 2012
 \*******************************************************************/
 
 #include <iostream>
+#include <unordered_set>
 
 #include <util/prefix.h>
 #include <util/file_util.h>
 
 #include "count_eloc.h"
 
-typedef hash_set_cont<irep_idt, irep_id_hash> linest;
-typedef hash_map_cont<irep_idt, linest, irep_id_hash> filest;
-typedef hash_map_cont<irep_idt, filest, irep_id_hash> working_dirst;
+typedef std::unordered_set<irep_idt, irep_id_hash> linest;
+typedef std::unordered_map<irep_idt, linest, irep_id_hash> filest;
+typedef std::unordered_map<irep_idt, filest, irep_id_hash> working_dirst;
 
 /*******************************************************************\
 
diff --git a/src/goto-instrument/cover.cpp b/src/goto-instrument/cover.cpp
index fba2f5fe4dc..5f02f91a0ee 100644
--- a/src/goto-instrument/cover.cpp
+++ b/src/goto-instrument/cover.cpp
@@ -12,7 +12,6 @@ Date: May 2016
 #include <iterator>
 
 #include <util/prefix.h>
-#include <util/i2string.h>
 #include <util/expr_util.h>
 
 #include "cover.h"
@@ -1120,7 +1119,7 @@ void instrument_cover_goals(
         unsigned block_nr=basic_blocks[i_it];
         if(blocks_done.insert(block_nr).second)
         {
-          std::string b=i2string(block_nr);
+          std::string b=std::to_string(block_nr);
           std::string id=id2string(i_it->function)+"#"+b;
           source_locationt source_location=
             basic_blocks.source_location_map[block_nr];
@@ -1165,7 +1164,7 @@ void instrument_cover_goals(
 
       if(i_it->is_goto() && !i_it->guard.is_true())
       {
-        std::string b=i2string(basic_blocks[i_it]);
+        std::string b=std::to_string(basic_blocks[i_it]);
         std::string true_comment=
           "function "+id2string(i_it->function)+" block "+b+" branch true";
         std::string false_comment=
diff --git a/src/goto-instrument/document_properties.cpp b/src/goto-instrument/document_properties.cpp
index 77e1df0a2cb..ad672236a5d 100644
--- a/src/goto-instrument/document_properties.cpp
+++ b/src/goto-instrument/document_properties.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <fstream>
 
 #include <util/string2int.h>
-#include <util/i2string.h>
 
 #include <ansi-c/expr2c.h>
 
@@ -286,7 +285,7 @@ void document_propertiest::get_code(
   for(std::list<linet>::iterator it=lines.begin();
       it!=lines.end(); it++)
   {
-    std::string line_no=i2string(it->line_number);
+    std::string line_no=std::to_string(it->line_number);
 
     std::string tmp;
 
diff --git a/src/goto-instrument/dump_c.cpp b/src/goto-instrument/dump_c.cpp
index 1d6d7cc712e..7fcd310fa31 100644
--- a/src/goto-instrument/dump_c.cpp
+++ b/src/goto-instrument/dump_c.cpp
@@ -14,7 +14,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/suffix.h>
 #include <util/find_symbols.h>
 #include <util/base_type.h>
-#include <util/i2string.h>
 #include <util/cprover_prefix.h>
 
 #include <ansi-c/ansi_c_language.h>
@@ -102,7 +101,7 @@ void dump_ct::operator()(std::ostream &os)
   forall_symbols(it, symbols_transparent.symbols)
     copied_symbol_table.add(it->second);
 
-  typedef hash_map_cont<irep_idt, unsigned, irep_id_hash> unique_tagst;
+  typedef std::unordered_map<irep_idt, unsigned, irep_id_hash> unique_tagst;
   unique_tagst unique_tags;
 
   // add tags to anonymous union/struct/enum,
@@ -148,7 +147,7 @@ void dump_ct::operator()(std::ostream &os)
           unique_entry=unique_tags.insert(std::make_pair(new_tag, 0)))
       {
         new_tag=new_tag_base+"$"+
-          i2string(unique_entry.first->second);
+          std::to_string(unique_entry.first->second);
         ++(unique_entry.first->second);
       }
 
diff --git a/src/goto-instrument/dump_c_class.h b/src/goto-instrument/dump_c_class.h
index a84841ca9b9..6bb7b79638e 100644
--- a/src/goto-instrument/dump_c_class.h
+++ b/src/goto-instrument/dump_c_class.h
@@ -46,16 +46,16 @@ class dump_ct
   const namespacet ns;
   languaget *language;
 
-  typedef hash_set_cont<irep_idt, irep_id_hash> convertedt;
+  typedef std::unordered_set<irep_idt, irep_id_hash> convertedt;
   convertedt converted_compound, converted_global, converted_enum;
 
   std::set<std::string> system_headers;
 
-  typedef hash_map_cont<irep_idt, std::string, irep_id_hash>
+  typedef std::unordered_map<irep_idt, std::string, irep_id_hash>
     system_library_mapt;
   system_library_mapt system_library_map;
 
-  typedef hash_map_cont<irep_idt, irep_idt, irep_id_hash>
+  typedef std::unordered_map<irep_idt, irep_idt, irep_id_hash>
     declared_enum_constants_mapt;
   declared_enum_constants_mapt declared_enum_constants;
 
@@ -102,7 +102,7 @@ class dump_ct
     const typet &type,
     std::ostream &os);
 
-  typedef hash_map_cont<irep_idt, code_declt, irep_id_hash>
+  typedef std::unordered_map<irep_idt, code_declt, irep_id_hash>
           local_static_declst;
 
   void convert_global_variable(
diff --git a/src/goto-instrument/full_slicer.cpp b/src/goto-instrument/full_slicer.cpp
index ede5bfb2676..04f4b97a1ea 100644
--- a/src/goto-instrument/full_slicer.cpp
+++ b/src/goto-instrument/full_slicer.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/find_symbols.h>
 #include <util/cprover_prefix.h>
 #ifdef DEBUG_FULL_SLICERT
-#include <util/i2string.h>
 #endif
 
 #include <goto-programs/remove_skip.h>
@@ -409,7 +408,7 @@ void full_slicert::operator()(
 #ifdef DEBUG_FULL_SLICERT
         else
         {
-          std::string c="ins:"+i2string(i_it->location_number);
+          std::string c="ins:"+std::to_string(i_it->location_number);
           c+=" req by:";
           for(std::set<unsigned>::const_iterator
               req_it=cfg[e].required_by.begin();
@@ -417,7 +416,7 @@ void full_slicert::operator()(
               ++req_it)
           {
             if(req_it!=cfg[e].required_by.begin()) c+=",";
-            c+=i2string(*req_it);
+            c+=std::to_string(*req_it);
           }
           i_it->source_location.set_column(c);  // for show-goto-functions
           i_it->source_location.set_comment(c); // for dump-c
diff --git a/src/goto-instrument/full_slicer_class.h b/src/goto-instrument/full_slicer_class.h
index 5ba76686d3f..bc743a7830d 100644
--- a/src/goto-instrument/full_slicer_class.h
+++ b/src/goto-instrument/full_slicer_class.h
@@ -67,7 +67,7 @@ class full_slicert
   typedef std::vector<cfgt::entryt> dep_node_to_cfgt;
   typedef std::stack<cfgt::entryt> queuet;
   typedef std::list<cfgt::entryt> jumpst;
-  typedef hash_map_cont<irep_idt, queuet, irep_id_hash> decl_deadt;
+  typedef std::unordered_map<irep_idt, queuet, irep_id_hash> decl_deadt;
 
   void fixedpoint(
     goto_functionst &goto_functions,
diff --git a/src/goto-instrument/goto_instrument_parse_options.cpp b/src/goto-instrument/goto_instrument_parse_options.cpp
index 23d681c5644..37b223e3535 100644
--- a/src/goto-instrument/goto_instrument_parse_options.cpp
+++ b/src/goto-instrument/goto_instrument_parse_options.cpp
@@ -158,7 +158,7 @@ int goto_instrument_parse_optionst::doit()
         int k=-1;
 
         if(unwind)
-          k=safe_string2int (cmdline.get_value("unwind"));
+          k=std::stoi(cmdline.get_value("unwind"));
 
         unwind_sett unwind_set;
 
diff --git a/src/goto-instrument/goto_program2code.cpp b/src/goto-instrument/goto_program2code.cpp
index edcc18a3792..e1698675af4 100644
--- a/src/goto-instrument/goto_program2code.cpp
+++ b/src/goto-instrument/goto_program2code.cpp
@@ -14,7 +14,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/find_symbols.h>
 #include <util/arith_tools.h>
 #include <util/type_eq.h>
-#include <util/i2string.h>
 
 #include "goto_program2code.h"
 
@@ -2306,10 +2305,10 @@ void goto_program2codet::cleanup_expr(exprt &expr, bool no_typecast)
         {
           unsigned count;
           for(count=0;
-              symbol_table.symbols.find("nondet_"+i2string(count))!=
+              symbol_table.symbols.find("nondet_"+std::to_string(count))!=
               symbol_table.symbols.end();
               count++);
-          base_name="nondet_"+i2string(count);
+          base_name="nondet_"+std::to_string(count);
         }
 
         code_typet code_type;
diff --git a/src/goto-instrument/goto_program2code.h b/src/goto-instrument/goto_program2code.h
index 02346e388ef..7d04c4accd4 100644
--- a/src/goto-instrument/goto_program2code.h
+++ b/src/goto-instrument/goto_program2code.h
@@ -16,9 +16,9 @@ Author: Daniel Kroening, kroening@kroening.com
 class goto_program2codet
 {
   typedef std::list<irep_idt> id_listt;
-  typedef hash_set_cont<irep_idt,irep_id_hash> id_sett;
+  typedef std::unordered_set<irep_idt,irep_id_hash> id_sett;
   typedef std::map<goto_programt::const_targett, goto_programt::const_targett> loopt;
-  typedef hash_map_cont<irep_idt, unsigned, irep_id_hash> dead_mapt;
+  typedef std::unordered_map<irep_idt, unsigned, irep_id_hash> dead_mapt;
   typedef std::list<std::pair<goto_programt::const_targett, bool> >
     loop_last_stackt;
 
@@ -78,7 +78,7 @@ class goto_program2codet
   id_listt &local_static;
   id_listt &type_names;
   std::set<std::string> &system_headers;
-  hash_set_cont<exprt, irep_hash> va_list_expr;
+  std::unordered_set<exprt, irep_hash> va_list_expr;
 
   natural_loopst loops;
   loopt loop_map;
diff --git a/src/goto-instrument/mmio.cpp b/src/goto-instrument/mmio.cpp
index 78ab7648cd2..098e8378e18 100644
--- a/src/goto-instrument/mmio.cpp
+++ b/src/goto-instrument/mmio.cpp
@@ -14,7 +14,6 @@ Date: September 2011
 #include <goto-programs/goto_functions.h>
 
 #if 0
-#include <util/hash_cont.h>
 #include <util/std_expr.h>
 #include <util/expr_util.h>
 #include <util/guard.h>
diff --git a/src/goto-instrument/race_check.cpp b/src/goto-instrument/race_check.cpp
index 6c15573ec27..3ca605b55c6 100644
--- a/src/goto-instrument/race_check.cpp
+++ b/src/goto-instrument/race_check.cpp
@@ -8,7 +8,6 @@ Date: February 2006
 
 \*******************************************************************/
 
-#include <util/hash_cont.h>
 #include <util/std_expr.h>
 #include <util/guard.h>
 #include <util/symbol_table.h>
diff --git a/src/goto-instrument/reachability_slicer.cpp b/src/goto-instrument/reachability_slicer.cpp
index 9f30f74b2d2..c502c2a33ae 100644
--- a/src/goto-instrument/reachability_slicer.cpp
+++ b/src/goto-instrument/reachability_slicer.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <stack>
 
-#include <util/i2string.h>
 
 #include <goto-programs/remove_skip.h>
 #include <goto-programs/remove_unreachable.h>
diff --git a/src/goto-instrument/rw_set.h b/src/goto-instrument/rw_set.h
index 129607487a0..4719ca6ed3d 100644
--- a/src/goto-instrument/rw_set.h
+++ b/src/goto-instrument/rw_set.h
@@ -15,7 +15,6 @@ Date: February 2006
 #include <vector>
 #include <set>
 
-#include <util/hash_cont.h>
 #include <util/guard.h>
 #include <util/std_code.h>
 #include <util/namespace.h>
@@ -51,7 +50,7 @@ class rw_set_baset
     }
   };
 
-  typedef hash_map_cont<irep_idt, entryt, irep_id_hash> entriest;
+  typedef std::unordered_map<irep_idt, entryt, irep_id_hash> entriest;
   entriest r_entries, w_entries;
 
   void swap(rw_set_baset &other)
diff --git a/src/goto-instrument/show_locations.cpp b/src/goto-instrument/show_locations.cpp
index 35ec08d9766..6527a29d437 100644
--- a/src/goto-instrument/show_locations.cpp
+++ b/src/goto-instrument/show_locations.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <iostream>
 
 #include <util/xml.h>
-#include <util/i2string.h>
 #include <util/xml_irep.h>
 
 #include <langapi/language_util.h>
@@ -46,7 +45,7 @@ void show_locations(
       {
         xmlt xml("program_location");
         xml.new_element("function").data=id2string(function_id);
-        xml.new_element("id").data=i2string(it->location_number);
+        xml.new_element("id").data=std::to_string(it->location_number);
 
         xmlt &l=xml.new_element();
         l.name="location";
diff --git a/src/goto-instrument/stack_depth.cpp b/src/goto-instrument/stack_depth.cpp
index d281f72210f..36f0d486773 100644
--- a/src/goto-instrument/stack_depth.cpp
+++ b/src/goto-instrument/stack_depth.cpp
@@ -13,7 +13,6 @@ Date: November 2011
 #include <util/std_types.h>
 #include <util/arith_tools.h>
 #include <util/cprover_prefix.h>
-#include <util/i2string.h>
 
 #include <goto-programs/goto_functions.h>
 
@@ -80,7 +79,7 @@ void stack_depth(
   assert_ins->source_location=first->source_location;
   assert_ins->function=first->function;
 
-  assert_ins->source_location.set_comment("Stack depth exceeds "+i2string(i_depth));
+  assert_ins->source_location.set_comment("Stack depth exceeds "+std::to_string(i_depth));
   assert_ins->source_location.set_property_class("stack-depth");
 
   goto_programt::targett plus_ins=goto_program.insert_before(first);
diff --git a/src/goto-instrument/unwind.cpp b/src/goto-instrument/unwind.cpp
index 6d33bbe3a11..54fd4ec399f 100644
--- a/src/goto-instrument/unwind.cpp
+++ b/src/goto-instrument/unwind.cpp
@@ -472,9 +472,9 @@ jsont goto_unwindt::unwind_logt::output_log_json() const
     goto_programt::const_targett target=it->first;
     unsigned location_number=it->second;
 
-    object["original_location_number"]=json_numbert(i2string(
+    object["original_location_number"]=json_numbert(std::to_string(
       location_number));
-    object["new_location_number"]=json_numbert(i2string(
+    object["new_location_number"]=json_numbert(std::to_string(
       target->location_number));
   }
 
diff --git a/src/goto-instrument/unwind.h b/src/goto-instrument/unwind.h
index ec7613e99c1..ccd83bac589 100644
--- a/src/goto-instrument/unwind.h
+++ b/src/goto-instrument/unwind.h
@@ -10,7 +10,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_GOTO_INSTRUMENT_UNWIND_H
 #define CPROVER_GOTO_INSTRUMENT_UNWIND_H
 
-#include <util/i2string.h>
 #include <util/json.h>
 #include <util/json_expr.h>
 #include <goto-programs/goto_program.h>
diff --git a/src/goto-instrument/wmm/event_graph.cpp b/src/goto-instrument/wmm/event_graph.cpp
index 79ed0b6a13f..f1d63cd33cd 100644
--- a/src/goto-instrument/wmm/event_graph.cpp
+++ b/src/goto-instrument/wmm/event_graph.cpp
@@ -10,7 +10,6 @@ Date: 2012
 
 #include "event_graph.h"
 
-#include <util/i2string.h>
 #include <util/message.h>
 
 #include <fstream>
@@ -1121,7 +1120,7 @@ std::string event_grapht::critical_cyclet::print() const
 {
   std::string cycle = "Cycle: ";
   for(const_iterator it=begin(); it!=end(); ++it)
-    cycle += i2string(egraph[*it].id) + "; ";
+    cycle += std::to_string(egraph[*it].id) + "; ";
   return cycle + " End of cycle.";
 }
 
@@ -1230,7 +1229,7 @@ std::string event_grapht::critical_cyclet::print_output() const
     const abstract_eventt& it_evt=egraph[*it];
     cycle += id2string(it_evt.variable) + " (";
     cycle += it_evt.source_location.as_string();
-    cycle += " thread " + i2string(it_evt.thread) + ") ";
+    cycle += " thread " + std::to_string(it_evt.thread) + ") ";
   }
   return cycle;
 }
@@ -1261,15 +1260,15 @@ std::string event_grapht::critical_cyclet::print_detail(
       + " (" + it_evt.source_location.as_string()  + ")";
     if(map_var2id.find(var_name)!=map_var2id.end())
     {
-      cycle += "t" + i2string(it_evt.thread) + " (";
+      cycle += "t" + std::to_string(it_evt.thread) + " (";
       cycle += map_var2id[var_name] + ") ";
     }
     else
     {
-      const std::string new_id = "var@" + i2string(map_var2id.size());
+      const std::string new_id = "var@" + std::to_string(map_var2id.size());
       map_var2id[var_name] = new_id;
       map_id2var[new_id] = var_name;
-      cycle += "t" + i2string(it_evt.thread) + " (";
+      cycle += "t" + std::to_string(it_evt.thread) + " (";
       cycle += new_id + ") ";
     }
   }
diff --git a/src/goto-instrument/wmm/goto2graph.cpp b/src/goto-instrument/wmm/goto2graph.cpp
index 59e7f97f903..c157f07c1ac 100644
--- a/src/goto-instrument/wmm/goto2graph.cpp
+++ b/src/goto-instrument/wmm/goto2graph.cpp
@@ -20,7 +20,6 @@ Date: 2012
 #include <util/cprover_prefix.h>
 #include <util/options.h>
 #include <util/message.h>
-#include <util/i2string.h>
 #include <util/std_expr.h>
 
 #include "../rw_set.h"
@@ -1770,7 +1769,7 @@ void instrumentert::print_outputs(memory_modelt model, bool hide_internals)
     for(unsigned i=0; i<num_sccs; i++)
     {
       std::ofstream local_dot;
-      std::string name = "scc_" + i2string(i) + ".dot";
+      std::string name = "scc_" + std::to_string(i) + ".dot";
       local_dot.open(name.c_str());
 
       local_dot << "digraph G {" << std::endl;
diff --git a/src/goto-instrument/wmm/instrumenter_strategies.cpp b/src/goto-instrument/wmm/instrumenter_strategies.cpp
index f2e98d5d8f0..f5880d73623 100644
--- a/src/goto-instrument/wmm/instrumenter_strategies.cpp
+++ b/src/goto-instrument/wmm/instrumenter_strategies.cpp
@@ -11,7 +11,6 @@ Date: 2012
 #include <string>
 #include <fstream>
 
-#include <util/i2string.h>
 
 #include "goto2graph.h"
 
@@ -327,7 +326,7 @@ void inline instrumentert::instrument_minimum_interference_inserter(
     ++e_i)
   {
     ++i;
-    std::string name="e_"+i2string(i);
+    std::string name="e_"+std::to_string(i);
     glp_set_col_name(lp, i, name.c_str());
     glp_set_col_bnds(lp, i, GLP_LO, 0.0, 0.0);
     glp_set_obj_coef(lp, i, cost(*e_i));
@@ -343,7 +342,7 @@ void inline instrumentert::instrument_minimum_interference_inserter(
     ++C_j)
   {
     ++i;
-    std::string name="C_"+i2string(i);
+    std::string name="C_"+std::to_string(i);
     glp_set_row_name(lp, i, name.c_str());
     glp_set_row_bnds(lp, i, GLP_LO, 1.0, 0.0); /* >= 1*/
   }
diff --git a/src/goto-instrument/wmm/shared_buffers.cpp b/src/goto-instrument/wmm/shared_buffers.cpp
index 4bc6236768a..b008f5148aa 100644
--- a/src/goto-instrument/wmm/shared_buffers.cpp
+++ b/src/goto-instrument/wmm/shared_buffers.cpp
@@ -1,4 +1,3 @@
-#include <util/i2string.h>
 
 #include "shared_buffers.h"
 #include "fence.h"
@@ -19,8 +18,8 @@ Function: shared_buffert::unique
 
 std::string shared_bufferst::unique (void)
 {
-  message.debug()<<"$fresh#"+i2string(uniq)<<messaget::eom;
-  return "$fresh#"+i2string(uniq++);
+  message.debug()<<"$fresh#"+std::to_string(uniq)<<messaget::eom;
+  return "$fresh#"+std::to_string(uniq++);
 }
 
 /*******************************************************************\
@@ -70,10 +69,10 @@ const shared_bufferst::varst &shared_bufferst::operator()(const irep_idt &object
   {
     vars.r_buff0_thds.push_back(
       shared_bufferst::add(
-        object, symbol.base_name, "$r_buff0_thd"+i2string(cnt), bool_typet()));
+        object, symbol.base_name, "$r_buff0_thd"+std::to_string(cnt), bool_typet()));
     vars.r_buff1_thds.push_back(
       shared_bufferst::add(
-        object, symbol.base_name, "$r_buff1_thd"+i2string(cnt), bool_typet()));
+        object, symbol.base_name, "$r_buff1_thd"+std::to_string(cnt), bool_typet()));
   }
 
   return vars;
diff --git a/src/goto-instrument/wmm/weak_memory.cpp b/src/goto-instrument/wmm/weak_memory.cpp
index 8a15cf532b8..e1dc7f101d0 100644
--- a/src/goto-instrument/wmm/weak_memory.cpp
+++ b/src/goto-instrument/wmm/weak_memory.cpp
@@ -20,7 +20,6 @@ Date: September 2011
 
 #include <util/cprover_prefix.h>
 #include <util/prefix.h>
-#include <util/i2string.h>
 #include <util/message.h>
 
 #include <goto-programs/remove_skip.h>
@@ -79,7 +78,7 @@ void introduce_temporaries(
 
       symbolt new_symbol;
       new_symbol.base_name="$tmp_guard";
-      new_symbol.name=id2string(function)+"$tmp_guard"+i2string(tmp_counter++);
+      new_symbol.name=id2string(function)+"$tmp_guard"+std::to_string(tmp_counter++);
       new_symbol.type=bool_typet();
       new_symbol.is_static_lifetime=true;
       new_symbol.is_thread_local=true;
diff --git a/src/goto-programs/builtin_functions.cpp b/src/goto-programs/builtin_functions.cpp
index 2f90b0f8443..fdf09c2c670 100644
--- a/src/goto-programs/builtin_functions.cpp
+++ b/src/goto-programs/builtin_functions.cpp
@@ -8,7 +8,7 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
-#include <util/i2string.h>
+#include <util/rational.h>
 #include <util/replace_expr.h>
 #include <util/expr_util.h>
 #include <util/rational_tools.h>
@@ -22,7 +22,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/symbol.h>
 #include <util/pointer_predicates.h>
 #include <util/pointer_offset_size.h>
-#include <util/namespace_utils.h>
 
 #include <linking/zero_initializer.h>
 
diff --git a/src/goto-programs/goto_clean_expr.cpp b/src/goto-programs/goto_clean_expr.cpp
index c97a11f3f8f..ff9a8068c34 100644
--- a/src/goto-programs/goto_clean_expr.cpp
+++ b/src/goto-programs/goto_clean_expr.cpp
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/std_expr.h>
 #include <util/rename.h>
 #include <util/cprover_prefix.h>
-#include <util/i2string.h>
 
 #include <ansi-c/c_types.h>
 
@@ -40,7 +39,7 @@ symbol_exprt goto_convertt::make_compound_literal(
 
   do
   {
-    new_symbol.base_name="literal$"+i2string(++temporary_counter);
+    new_symbol.base_name="literal$"+std::to_string(++temporary_counter);
     new_symbol.name=tmp_symbol_prefix+id2string(new_symbol.base_name);
     new_symbol.is_static_lifetime=source_location.get_function().empty();
     new_symbol.value=expr;
diff --git a/src/goto-programs/goto_convert.cpp b/src/goto-programs/goto_convert.cpp
index 78b5cc9067f..2a1c8bad6f5 100644
--- a/src/goto-programs/goto_convert.cpp
+++ b/src/goto-programs/goto_convert.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
-#include <util/i2string.h>
 #include <util/cprover_prefix.h>
 #include <util/expr_util.h>
 #include <util/prefix.h>
@@ -2566,7 +2565,7 @@ symbolt &goto_convertt::new_tmp_symbol(
 
   do
   {
-    new_symbol.base_name="tmp_"+suffix+"$"+i2string(++temporary_counter);
+    new_symbol.base_name="tmp_"+suffix+"$"+std::to_string(++temporary_counter);
     new_symbol.name=tmp_symbol_prefix+id2string(new_symbol.base_name);
     new_symbol.type=type;
     new_symbol.location=source_location;
diff --git a/src/goto-programs/goto_convert_function_call.cpp b/src/goto-programs/goto_convert_function_call.cpp
index 78d6d8b762e..badeebc29fb 100644
--- a/src/goto-programs/goto_convert_function_call.cpp
+++ b/src/goto-programs/goto_convert_function_call.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
-#include <util/i2string.h>
 #include <util/replace_expr.h>
 #include <util/expr_util.h>
 #include <util/source_location.h>
diff --git a/src/goto-programs/goto_convert_new_switch_case.cpp b/src/goto-programs/goto_convert_new_switch_case.cpp
index 7f0b0007e6e..1bbde509419 100644
--- a/src/goto-programs/goto_convert_new_switch_case.cpp
+++ b/src/goto-programs/goto_convert_new_switch_case.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
-#include <util/i2string.h>
 #include <util/cprover_prefix.h>
 #include <util/expr_util.h>
 #include <util/prefix.h>
@@ -2509,7 +2508,7 @@ symbolt &goto_convertt::new_tmp_symbol(
 
   do
   {
-    new_symbol.base_name="tmp_"+suffix+"$"+i2string(++temporary_counter);
+    new_symbol.base_name="tmp_"+suffix+"$"+std::to_string(++temporary_counter);
     new_symbol.name=tmp_symbol_prefix+id2string(new_symbol.base_name);
     new_symbol.type=type;
     new_symbol.location=source_location;
diff --git a/src/goto-programs/goto_convert_side_effect.cpp b/src/goto-programs/goto_convert_side_effect.cpp
index 4e51390026b..da2d8ca7cad 100644
--- a/src/goto-programs/goto_convert_side_effect.cpp
+++ b/src/goto-programs/goto_convert_side_effect.cpp
@@ -10,7 +10,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/std_expr.h>
 #include <util/rename.h>
 #include <util/cprover_prefix.h>
-#include <util/i2string.h>
 #include <util/symbol.h>
 
 #include <ansi-c/c_types.h>
@@ -427,7 +426,7 @@ void goto_convertt::remove_function_call(
 
     new_base_name+='_';
     new_base_name+=id2string(symbol.base_name);
-    new_base_name+="$"+i2string(++temporary_counter);
+    new_base_name+="$"+std::to_string(++temporary_counter);
 
     new_symbol.base_name=new_base_name;
     new_symbol.mode=symbol.mode;
@@ -501,7 +500,7 @@ void goto_convertt::remove_cpp_new(
 
   auxiliary_symbolt new_symbol;
 
-  new_symbol.base_name="new_ptr$"+i2string(++temporary_counter);
+  new_symbol.base_name="new_ptr$"+std::to_string(++temporary_counter);
   new_symbol.type=expr.type();
   new_symbol.name=tmp_symbol_prefix+id2string(new_symbol.base_name);
 
@@ -576,7 +575,7 @@ void goto_convertt::remove_malloc(
   {
     auxiliary_symbolt new_symbol;
 
-    new_symbol.base_name="malloc_value$"+i2string(++temporary_counter);
+    new_symbol.base_name="malloc_value$"+std::to_string(++temporary_counter);
     new_symbol.type=expr.type();
     new_symbol.name=tmp_symbol_prefix+id2string(new_symbol.base_name);
     new_symbol.location=expr.source_location();
diff --git a/src/goto-programs/goto_inline_class.h b/src/goto-programs/goto_inline_class.h
index 88053ef932c..8ffb33d010b 100644
--- a/src/goto-programs/goto_inline_class.h
+++ b/src/goto-programs/goto_inline_class.h
@@ -9,6 +9,8 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_GOTO_PROGRAMS_GOTO_INLINE_CLASS_H
 #define CPROVER_GOTO_PROGRAMS_GOTO_INLINE_CLASS_H
 
+#include <unordered_set>
+
 #include <util/message.h>
 
 #include "goto_functions.h"
@@ -76,13 +78,13 @@ class goto_inlinet:public messaget
     const code_typet &code_type,
     goto_programt &dest);
 
-  typedef hash_set_cont<irep_idt, irep_id_hash> recursion_sett;
+  typedef std::unordered_set<irep_idt, irep_id_hash> recursion_sett;
   recursion_sett recursion_set;
 
-  typedef hash_set_cont<irep_idt, irep_id_hash> no_body_sett;
+  typedef std::unordered_set<irep_idt, irep_id_hash> no_body_sett;
   no_body_sett no_body_set;
 
-  typedef hash_set_cont<irep_idt, irep_id_hash> finished_inlining_sett;
+  typedef std::unordered_set<irep_idt, irep_id_hash> finished_inlining_sett;
   finished_inlining_sett finished_inlining_set;
 };
 
diff --git a/src/goto-programs/goto_program.cpp b/src/goto-programs/goto_program.cpp
index b83c1a10efd..f914488310a 100644
--- a/src/goto-programs/goto_program.cpp
+++ b/src/goto-programs/goto_program.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <ostream>
 
 #include <util/std_expr.h>
-#include <util/i2string.h>
 
 #include <langapi/language_util.h>
 
@@ -511,7 +510,7 @@ std::string as_string(
         gt_it++)
     {
       if(gt_it!=i.targets.begin()) result+=", ";
-      result+=i2string((*gt_it)->target_number);
+      result+=std::to_string((*gt_it)->target_number);
     }
     return result;
 
@@ -563,7 +562,7 @@ std::string as_string(
     result+="START THREAD ";
 
     if(i.targets.size()==1)
-      result+=i2string(i.targets.front()->target_number);
+      result+=std::to_string(i.targets.front()->target_number);
     return result;
 
   case END_THREAD:
diff --git a/src/goto-programs/goto_program_irep.cpp b/src/goto-programs/goto_program_irep.cpp
index cbf78acd295..efc76ea3069 100644
--- a/src/goto-programs/goto_program_irep.cpp
+++ b/src/goto-programs/goto_program_irep.cpp
@@ -11,7 +11,6 @@ Date: May 2007
 #include <iostream>
 
 #include <util/string2int.h>
-#include <util/i2string.h>
 
 #include "goto_program_irep.h"
 
@@ -49,7 +48,7 @@ void convert(const goto_programt::instructiont &instruction, irept &irep)
         it!=instruction.targets.end();
         it++)
     {
-      irept t(i2string((*it)->location_number));
+      irept t(std::to_string((*it)->location_number));
       tgts.move_to_sub(t);
     }
   }
diff --git a/src/goto-programs/goto_program_template.h b/src/goto-programs/goto_program_template.h
index 910603bdc39..e3fc77c328d 100644
--- a/src/goto-programs/goto_program_template.h
+++ b/src/goto-programs/goto_program_template.h
@@ -402,7 +402,7 @@ class goto_program_templatet
   inline static irep_idt loop_id(const_targett target)
   {
     return id2string(target->function)+"."+
-           i2string(target->loop_number);
+           std::to_string(target->loop_number);
   }
 
   //! Is the program empty?
diff --git a/src/goto-programs/graphml_witness.cpp b/src/goto-programs/graphml_witness.cpp
index f5236227de6..d9f73ec7ebb 100644
--- a/src/goto-programs/graphml_witness.cpp
+++ b/src/goto-programs/graphml_witness.cpp
@@ -7,7 +7,6 @@ Author: Daniel Kroening
 \*******************************************************************/
 
 #include <util/config.h>
-#include <util/i2string.h>
 #include <util/arith_tools.h>
 #include <util/prefix.h>
 #include <util/ssa_expr.h>
@@ -186,7 +185,7 @@ void graphml_witnesst::operator()(const goto_tracet &goto_trace)
 
     const graphmlt::node_indext node=graphml.add_node();
     graphml[node].node_name=
-      i2string(it->pc->location_number)+"."+i2string(it->step_nr);
+      std::to_string(it->pc->location_number)+"."+std::to_string(it->step_nr);
     graphml[node].file=source_location.get_file();
     graphml[node].line=source_location.get_line();
     graphml[node].thread_nr=it->thread_nr;
diff --git a/src/goto-programs/interpreter_class.h b/src/goto-programs/interpreter_class.h
index 94fab6ed8d4..9a3133e9f1c 100644
--- a/src/goto-programs/interpreter_class.h
+++ b/src/goto-programs/interpreter_class.h
@@ -36,7 +36,7 @@ class interpretert
   const namespacet ns;
   const goto_functionst &goto_functions;
 
-  typedef hash_map_cont<irep_idt, unsigned, irep_id_hash> memory_mapt;
+  typedef std::unordered_map<irep_idt, unsigned, irep_id_hash> memory_mapt;
   memory_mapt memory_map;
 
   class memory_cellt
diff --git a/src/goto-programs/json_goto_trace.cpp b/src/goto-programs/json_goto_trace.cpp
index 3d2cbf3c352..48964921aa7 100644
--- a/src/goto-programs/json_goto_trace.cpp
+++ b/src/goto-programs/json_goto_trace.cpp
@@ -10,7 +10,6 @@ Author: Daniel Kroening
 
 #include <cassert>
 
-#include <util/i2string.h>
 #include <util/json_expr.h>
 
 #include <langapi/language_util.h>
@@ -62,14 +61,14 @@ void convert(
         {
           property_id=
             id2string(it.pc->source_location.get_function())+".unwind."+
-            i2string(it.pc->loop_number);
+            std::to_string(it.pc->loop_number);
         }
 
         json_objectt &json_failure=dest_array.push_back().make_object();
 
         json_failure["stepType"]=json_stringt("failure");
         json_failure["hidden"]=jsont::json_boolean(it.hidden);
-        json_failure["thread"]=json_numbert(i2string(it.thread_nr));
+        json_failure["thread"]=json_numbert(std::to_string(it.thread_nr));
         json_failure["reason"]=json_stringt(id2string(it.comment));
         json_failure["property"]=json_stringt(id2string(property_id));
 
@@ -119,7 +118,7 @@ void convert(
         json_assignment["value"]=full_lhs_value;
         json_assignment["lhs"]=json_stringt(full_lhs_string);
         json_assignment["hidden"]=jsont::json_boolean(it.hidden);
-        json_assignment["thread"]=json_numbert(i2string(it.thread_nr));
+        json_assignment["thread"]=json_numbert(std::to_string(it.thread_nr));
 
         json_assignment["assignmentType"]=
           json_stringt(it.assignment_type==goto_trace_stept::ACTUAL_PARAMETER?
@@ -133,7 +132,7 @@ void convert(
 
         json_output["stepType"]=json_stringt("output");
         json_output["hidden"]=jsont::json_boolean(it.hidden);
-        json_output["thread"]=json_numbert(i2string(it.thread_nr));
+        json_output["thread"]=json_numbert(std::to_string(it.thread_nr));
         json_output["outputID"]=json_stringt(id2string(it.io_id));
 
         json_arrayt &json_values=json_output["values"].make_array();
@@ -157,7 +156,7 @@ void convert(
 
         json_input["stepType"]=json_stringt("input");
         json_input["hidden"]=jsont::json_boolean(it.hidden);
-        json_input["thread"]=json_numbert(i2string(it.thread_nr));
+        json_input["thread"]=json_numbert(std::to_string(it.thread_nr));
         json_input["inputID"]=json_stringt(id2string(it.io_id));
 
         json_arrayt &json_values=json_input["values"].make_array();
@@ -185,7 +184,7 @@ void convert(
 
         json_call_return["stepType"]=json_stringt(tag);
         json_call_return["hidden"]=jsont::json_boolean(it.hidden);
-        json_call_return["thread"]=json_numbert(i2string(it.thread_nr));
+        json_call_return["thread"]=json_numbert(std::to_string(it.thread_nr));
 
         const symbolt &symbol=ns.lookup(it.identifier);
         json_objectt &json_function=json_call_return["function"].make_object();
@@ -208,7 +207,7 @@ void convert(
           json_objectt &json_location_only=dest_array.push_back().make_object();
           json_location_only["stepType"]=json_stringt("location-only");
           json_location_only["hidden"]=jsont::json_boolean(it.hidden);
-          json_location_only["thread"]=json_numbert(i2string(it.thread_nr));
+          json_location_only["thread"]=json_numbert(std::to_string(it.thread_nr));
           json_location_only["sourceLocation"]=json_location;
         }
       }
diff --git a/src/goto-programs/loop_ids.cpp b/src/goto-programs/loop_ids.cpp
index 93119cecb93..30c0ce838f0 100644
--- a/src/goto-programs/loop_ids.cpp
+++ b/src/goto-programs/loop_ids.cpp
@@ -12,7 +12,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/xml_expr.h>
 #include <util/json.h>
 #include <util/json_expr.h>
-#include <util/i2string.h>
 
 #include "loop_ids.h"
 
@@ -81,7 +80,7 @@ void show_loop_ids(
         if(it->is_backwards_goto())
         {
           unsigned loop_id=it->loop_number;
-          std::string id=id2string(it->function)+"."+i2string(loop_id);
+          std::string id=id2string(it->function)+"."+std::to_string(loop_id);
 
           xmlt xml_loop("loop");
           xml_loop.set_attribute("name", id);
@@ -111,7 +110,7 @@ void show_loop_ids_json(
     if(it->is_backwards_goto())
     {
       unsigned loop_id=it->loop_number;
-      std::string id=id2string(it->function)+"."+i2string(loop_id);
+      std::string id=id2string(it->function)+"."+std::to_string(loop_id);
 
       json_objectt &loop=loops.push_back().make_object();
       loop["name"]=json_stringt(id);
diff --git a/src/goto-programs/read_goto_binary.cpp b/src/goto-programs/read_goto_binary.cpp
index cbc9a9af64d..9ae9ed5a29a 100644
--- a/src/goto-programs/read_goto_binary.cpp
+++ b/src/goto-programs/read_goto_binary.cpp
@@ -16,6 +16,7 @@ Module: Read Goto Programs
 #endif
 
 #include <fstream>
+#include <unordered_set>
 
 #include <util/message.h>
 #include <util/unicode.h>
@@ -284,7 +285,7 @@ static bool link_functions(
   const symbol_tablet &src_symbol_table,
   goto_functionst &src_functions,
   const rename_symbolt &rename_symbol,
-  const hash_set_cont<irep_idt, irep_id_hash> &weak_symbols)
+  const std::unordered_set<irep_idt, irep_id_hash> &weak_symbols)
 {
   namespacet ns(dest_symbol_table);
   namespacet src_ns(src_symbol_table);
@@ -409,7 +410,7 @@ bool read_object_and_link(
       message_handler))
     return true;
 
-  typedef hash_set_cont<irep_idt, irep_id_hash> id_sett;
+  typedef std::unordered_set<irep_idt, irep_id_hash> id_sett;
   id_sett weak_symbols;
   forall_symbols(it, symbol_table.symbols)
     if(it->second.is_weak)
diff --git a/src/goto-programs/remove_function_pointers.cpp b/src/goto-programs/remove_function_pointers.cpp
index 5054f351a05..a58770bd1c8 100644
--- a/src/goto-programs/remove_function_pointers.cpp
+++ b/src/goto-programs/remove_function_pointers.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
-#include <util/i2string.h>
 #include <util/replace_expr.h>
 #include <util/expr_util.h>
 #include <util/source_location.h>
@@ -138,7 +137,7 @@ symbolt &remove_function_pointerst::new_tmp_symbol()
 
   do
   {
-    new_symbol.base_name="tmp_return_val$"+i2string(++temporary_counter);
+    new_symbol.base_name="tmp_return_val$"+std::to_string(++temporary_counter);
     new_symbol.name="remove_function_pointers::"+id2string(new_symbol.base_name);
   } while(symbol_table.move(new_symbol, symbol_ptr));
 
diff --git a/src/goto-programs/set_properties.cpp b/src/goto-programs/set_properties.cpp
index d6949449411..095fb43d235 100644
--- a/src/goto-programs/set_properties.cpp
+++ b/src/goto-programs/set_properties.cpp
@@ -7,9 +7,8 @@ Author: Daniel Kroening, kroening@kroening.com
 \*******************************************************************/
 
 #include <algorithm>
+#include <unordered_set>
 
-#include <util/i2string.h>
-#include <util/hash_cont.h>
 
 #include "set_properties.h"
 
@@ -27,7 +26,7 @@ Function: set_properties
 
 void set_properties(
   goto_programt &goto_program,
-  hash_set_cont<irep_idt, irep_id_hash> &property_set)
+  std::unordered_set<irep_idt, irep_id_hash> &property_set)
 {
   for(goto_programt::instructionst::iterator
       it=goto_program.instructions.begin();
@@ -38,7 +37,7 @@ void set_properties(
 
     irep_idt property_id=it->source_location.get_property_id();
 
-    hash_set_cont<irep_idt, irep_id_hash>::iterator
+    std::unordered_set<irep_idt, irep_id_hash>::iterator
       c_it=property_set.find(property_id);
 
     if(c_it==property_set.end())
@@ -110,7 +109,7 @@ void label_properties(
 
     count++;
 
-    std::string property_id=prefix+i2string(count);
+    std::string property_id=prefix+std::to_string(count);
 
     it->source_location.set_property_id(property_id);
   }
@@ -169,7 +168,7 @@ void set_properties(
   goto_functionst &goto_functions,
   const std::list<std::string> &properties)
 {
-  hash_set_cont<irep_idt, irep_id_hash> property_set;
+  std::unordered_set<irep_idt, irep_id_hash> property_set;
 
   for(std::list<std::string>::const_iterator
       it=properties.begin();
diff --git a/src/goto-programs/show_goto_functions.cpp b/src/goto-programs/show_goto_functions.cpp
index 85733c43dba..ef600a748cc 100644
--- a/src/goto-programs/show_goto_functions.cpp
+++ b/src/goto-programs/show_goto_functions.cpp
@@ -10,7 +10,6 @@ Author: Peter Schrammel
 
 #include <util/xml.h>
 #include <util/json.h>
-#include <util/i2string.h>
 #include <util/xml_expr.h>
 #include <util/cprover_prefix.h>
 #include <util/prefix.h>
diff --git a/src/goto-programs/show_properties.cpp b/src/goto-programs/show_properties.cpp
index e8ea32ca682..fb078873f1d 100644
--- a/src/goto-programs/show_properties.cpp
+++ b/src/goto-programs/show_properties.cpp
@@ -12,7 +12,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/xml_expr.h>
 #include <util/json.h>
 #include <util/json_expr.h>
-#include <util/i2string.h>
 
 #include <langapi/language_util.h>
 
diff --git a/src/goto-programs/string_abstraction.cpp b/src/goto-programs/string_abstraction.cpp
index 229607ffa88..3c5e736e2b8 100644
--- a/src/goto-programs/string_abstraction.cpp
+++ b/src/goto-programs/string_abstraction.cpp
@@ -13,7 +13,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/expr_util.h>
 #include <util/message.h>
 #include <util/arith_tools.h>
-#include <util/i2string.h>
 #include <util/type_eq.h>
 
 #include <ansi-c/c_types.h>
@@ -379,7 +378,7 @@ Function: string_abstractiont::declare_define_locals
 
 void string_abstractiont::declare_define_locals(goto_programt &dest)
 {
-  typedef hash_map_cont<irep_idt, goto_programt::targett, irep_id_hash>
+  typedef std::unordered_map<irep_idt, goto_programt::targett, irep_id_hash>
     available_declst;
   available_declst available_decls;
 
@@ -1250,7 +1249,7 @@ exprt string_abstractiont::build_unknown(const typet &type, bool write)
   // create an uninitialized dummy symbol
   // because of a lack of contextual information we can't build a nice name
   // here, but moving that into locals should suffice for proper operation
-  irep_idt identifier="$tmp::nondet_str#str$"+i2string(++temporary_counter);
+  irep_idt identifier="$tmp::nondet_str#str$"+std::to_string(++temporary_counter);
   // ensure decl and initialization
   locals[identifier]=identifier;
 
diff --git a/src/goto-programs/string_abstraction.h b/src/goto-programs/string_abstraction.h
index 12e66893092..f3e3a3e0526 100644
--- a/src/goto-programs/string_abstraction.h
+++ b/src/goto-programs/string_abstraction.h
@@ -135,7 +135,7 @@ class string_abstractiont:public messaget
   typet string_struct;
   goto_programt initialization;
 
-  typedef hash_map_cont<irep_idt, irep_idt, irep_id_hash> localst;
+  typedef std::unordered_map<irep_idt, irep_idt, irep_id_hash> localst;
   localst locals;
 
   void abstract(goto_programt &dest);
diff --git a/src/goto-programs/wp.cpp b/src/goto-programs/wp.cpp
index a6e2c7d55c6..8b24655f304 100644
--- a/src/goto-programs/wp.cpp
+++ b/src/goto-programs/wp.cpp
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/std_expr.h>
 #include <util/std_code.h>
 #include <util/base_type.h>
-#include <util/i2string.h>
 
 #include "wp.h"
 
@@ -63,7 +62,7 @@ void approximate_nondet_rec(exprt &dest, unsigned &count)
      to_side_effect_expr(dest).get_statement()==ID_nondet)
   {
     count++;
-    dest.set(ID_identifier, "wp::nondet::"+i2string(count));
+    dest.set(ID_identifier, "wp::nondet::"+std::to_string(count));
     dest.id(ID_nondet_symbol);
     return;
   }
diff --git a/src/goto-programs/xml_goto_trace.cpp b/src/goto-programs/xml_goto_trace.cpp
index 161bc399cca..ac46ba776d7 100644
--- a/src/goto-programs/xml_goto_trace.cpp
+++ b/src/goto-programs/xml_goto_trace.cpp
@@ -11,7 +11,6 @@ Author: Daniel Kroening
 #include <cassert>
 
 #include <util/xml_expr.h>
-#include <util/i2string.h>
 #include <util/symbol.h>
 
 #include <ansi-c/printf_formatter.h>
@@ -61,14 +60,14 @@ void convert(
         {
           property_id=
             id2string(it.pc->source_location.get_function())+".unwind."+
-            i2string(it.pc->loop_number);
+            std::to_string(it.pc->loop_number);
         }
 
         xmlt &xml_failure=dest.new_element("failure");
 
         xml_failure.set_attribute_bool("hidden", it.hidden);
-        xml_failure.set_attribute("thread", i2string(it.thread_nr));
-        xml_failure.set_attribute("step_nr", i2string(it.step_nr));
+        xml_failure.set_attribute("thread", std::to_string(it.thread_nr));
+        xml_failure.set_attribute("step_nr", std::to_string(it.step_nr));
         xml_failure.set_attribute("reason", id2string(it.comment));
         xml_failure.set_attribute("property", id2string(property_id));
 
@@ -120,11 +119,11 @@ void convert(
         xml_assignment.new_element("value").data=value_string;
 
         xml_assignment.set_attribute_bool("hidden", it.hidden);
-        xml_assignment.set_attribute("thread", i2string(it.thread_nr));
+        xml_assignment.set_attribute("thread", std::to_string(it.thread_nr));
         xml_assignment.set_attribute("identifier", id2string(identifier));
         xml_assignment.set_attribute("base_name", id2string(base_name));
         xml_assignment.set_attribute("display_name", id2string(display_name));
-        xml_assignment.set_attribute("step_nr", i2string(it.step_nr));
+        xml_assignment.set_attribute("step_nr", std::to_string(it.step_nr));
 
         xml_assignment.set_attribute("assignment_type",
           it.assignment_type==goto_trace_stept::ACTUAL_PARAMETER?"actual_parameter":
@@ -145,8 +144,8 @@ void convert(
         xml_output.new_element("text").data=text;
 
         xml_output.set_attribute_bool("hidden", it.hidden);
-        xml_output.set_attribute("thread", i2string(it.thread_nr));
-        xml_output.set_attribute("step_nr", i2string(it.step_nr));
+        xml_output.set_attribute("thread", std::to_string(it.thread_nr));
+        xml_output.set_attribute("step_nr", std::to_string(it.step_nr));
 
         if(xml_location.name!="")
           xml_output.new_element().swap(xml_location);
@@ -166,8 +165,8 @@ void convert(
         xml_input.new_element("input_id").data=id2string(it.io_id);
 
         xml_input.set_attribute_bool("hidden", it.hidden);
-        xml_input.set_attribute("thread", i2string(it.thread_nr));
-        xml_input.set_attribute("step_nr", i2string(it.step_nr));
+        xml_input.set_attribute("thread", std::to_string(it.thread_nr));
+        xml_input.set_attribute("step_nr", std::to_string(it.step_nr));
 
         for(const auto & l_it : it.io_args)
         {
@@ -189,8 +188,8 @@ void convert(
         xmlt &xml_call_return=dest.new_element(tag);
 
         xml_call_return.set_attribute_bool("hidden", it.hidden);
-        xml_call_return.set_attribute("thread", i2string(it.thread_nr));
-        xml_call_return.set_attribute("step_nr", i2string(it.step_nr));
+        xml_call_return.set_attribute("thread", std::to_string(it.thread_nr));
+        xml_call_return.set_attribute("step_nr", std::to_string(it.step_nr));
 
         const symbolt &symbol=ns.lookup(it.identifier);
         xmlt &xml_function=xml_call_return.new_element("function");
@@ -212,8 +211,8 @@ void convert(
           xmlt &xml_location_only=dest.new_element("location-only");
 
           xml_location_only.set_attribute_bool("hidden", it.hidden);
-          xml_location_only.set_attribute("thread", i2string(it.thread_nr));
-          xml_location_only.set_attribute("step_nr", i2string(it.step_nr));
+          xml_location_only.set_attribute("thread", std::to_string(it.thread_nr));
+          xml_location_only.set_attribute("step_nr", std::to_string(it.step_nr));
 
           xml_location_only.new_element().swap(xml_location);
         }
diff --git a/src/goto-symex/auto_objects.cpp b/src/goto-symex/auto_objects.cpp
index b06a86691ec..a561984bf30 100644
--- a/src/goto-symex/auto_objects.cpp
+++ b/src/goto-symex/auto_objects.cpp
@@ -6,7 +6,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/prefix.h>
 #include <util/cprover_prefix.h>
 #include <util/symbol_table.h>
@@ -33,7 +32,7 @@ exprt goto_symext::make_auto_object(const typet &type)
   // produce auto-object symbol
   symbolt symbol;
 
-  symbol.base_name="auto_object"+i2string(dynamic_counter);
+  symbol.base_name="auto_object"+std::to_string(dynamic_counter);
   symbol.name="symex::"+id2string(symbol.base_name);
   symbol.is_lvalue=true;
   symbol.type=type;
diff --git a/src/goto-symex/goto_symex.cpp b/src/goto-symex/goto_symex.cpp
index fa6d5841817..a3d55220e8d 100644
--- a/src/goto-symex/goto_symex.cpp
+++ b/src/goto-symex/goto_symex.cpp
@@ -49,7 +49,7 @@ void goto_symext::replace_nondet(exprt &expr)
      expr.get(ID_statement)==ID_nondet)
   {
     exprt new_expr(ID_nondet_symbol, expr.type());
-    new_expr.set(ID_identifier, "symex::nondet"+i2string(nondet_count++));
+    new_expr.set(ID_identifier, "symex::nondet"+std::to_string(nondet_count++));
     new_expr.add_source_location()=expr.source_location();
     expr.swap(new_expr);
   }
diff --git a/src/goto-symex/goto_symex_state.h b/src/goto-symex/goto_symex_state.h
index 2063d210764..cf4cdb38f5a 100644
--- a/src/goto-symex/goto_symex_state.h
+++ b/src/goto-symex/goto_symex_state.h
@@ -10,10 +10,10 @@ Author: Daniel Kroening, kroening@kroening.com
 #define CPROVER_GOTO_SYMEX_GOTO_SYMEX_STATE_H
 
 #include <cassert>
+#include <unordered_set>
 
 #include <util/guard.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/ssa_expr.h>
 
 #include <pointer-analysis/value_set.h>
@@ -64,7 +64,7 @@ class goto_symex_statet
       ++current_names[identifier].second;
     }
 
-    void get_variables(hash_set_cont<ssa_exprt, irep_hash> &vars) const
+    void get_variables(std::unordered_set<ssa_exprt, irep_hash> &vars) const
     {
       for(current_namest::const_iterator it=current_names.begin();
           it!=current_names.end();
@@ -173,7 +173,7 @@ class goto_symex_statet
   void get_l1_name(exprt &expr) const;
 
   // this maps L1 names to (L2) types
-  typedef hash_map_cont<irep_idt, typet, irep_id_hash> l1_typest;
+  typedef std::unordered_map<irep_idt, typet, irep_id_hash> l1_typest;
   l1_typest l1_types;
 
 public:
@@ -202,7 +202,7 @@ class goto_symex_statet
     }
 
     // the below replicate levelt2 member functions
-    void level2_get_variables(hash_set_cont<ssa_exprt, irep_hash> &vars) const
+    void level2_get_variables(std::unordered_set<ssa_exprt, irep_hash> &vars) const
     {
       for(level2t::current_namest::const_iterator
           it=level2_current_names.begin();
@@ -264,7 +264,7 @@ class goto_symex_statet
       unsigned count;
       bool is_recursion;
     };
-    typedef hash_map_cont<irep_idt, loop_infot, irep_id_hash>
+    typedef std::unordered_map<irep_idt, loop_infot, irep_id_hash>
       loop_iterationst;
     loop_iterationst loop_iterations;
   };
@@ -302,9 +302,9 @@ class goto_symex_statet
   // threads
   unsigned atomic_section_id;
   typedef std::pair<unsigned, std::list<guardt> > a_s_r_entryt;
-  typedef hash_map_cont<ssa_exprt, a_s_r_entryt, irep_hash> read_in_atomic_sectiont;
+  typedef std::unordered_map<ssa_exprt, a_s_r_entryt, irep_hash> read_in_atomic_sectiont;
   typedef std::list<guardt> a_s_w_entryt;
-  typedef hash_map_cont<ssa_exprt, a_s_w_entryt, irep_hash> written_in_atomic_sectiont;
+  typedef std::unordered_map<ssa_exprt, a_s_w_entryt, irep_hash> written_in_atomic_sectiont;
   read_in_atomic_sectiont read_in_atomic_section;
   written_in_atomic_sectiont written_in_atomic_section;
 
diff --git a/src/goto-symex/memory_model.cpp b/src/goto-symex/memory_model.cpp
index 702fefe57b6..77730a80d24 100644
--- a/src/goto-symex/memory_model.cpp
+++ b/src/goto-symex/memory_model.cpp
@@ -7,7 +7,6 @@ Author: Michael Tautschnig, michael.tautschnig@cs.ox.ac.uk
 \*******************************************************************/
 
 #include <util/std_expr.h>
-#include <util/i2string.h>
 
 #include "memory_model.h"
 
@@ -61,7 +60,7 @@ symbol_exprt memory_model_baset::nondet_bool_symbol(
   const std::string &prefix)
 {
   return symbol_exprt(
-    "memory_model::choice_"+prefix+i2string(var_cnt++),
+    "memory_model::choice_"+prefix+std::to_string(var_cnt++),
     bool_typet());
 }
 
diff --git a/src/goto-symex/memory_model_sc.cpp b/src/goto-symex/memory_model_sc.cpp
index eeeda91e2b6..0cac966402f 100644
--- a/src/goto-symex/memory_model_sc.cpp
+++ b/src/goto-symex/memory_model_sc.cpp
@@ -7,7 +7,6 @@ Author: Michael Tautschnig, michael.tautschnig@cs.ox.ac.uk
 \*******************************************************************/
 
 #include <util/std_expr.h>
-#include <util/i2string.h>
 
 #include "memory_model_sc.h"
 
diff --git a/src/goto-symex/partial_order_concurrency.cpp b/src/goto-symex/partial_order_concurrency.cpp
index e9c1eb72e95..0c39dbafc5f 100644
--- a/src/goto-symex/partial_order_concurrency.cpp
+++ b/src/goto-symex/partial_order_concurrency.cpp
@@ -8,7 +8,6 @@ Author: Michael Tautschnig, michael.tautschnig@cs.ox.ac.uk
 
 #include <limits>
 
-#include <util/i2string.h>
 #include <util/arith_tools.h>
 #include <util/simplify_expr.h>
 
@@ -62,7 +61,7 @@ Function: partial_order_concurrencyt::add_init_writes
 void partial_order_concurrencyt::add_init_writes(
   symex_target_equationt &equation)
 {
-  hash_set_cont<irep_idt, irep_id_hash> init_done;
+  std::unordered_set<irep_idt, irep_id_hash> init_done;
   bool spawn_seen=false;
 
   symex_target_equationt::SSA_stepst init_steps;
@@ -185,9 +184,9 @@ irep_idt partial_order_concurrencyt::rw_clock_id(
   axiomt axiom)
 {
   if(event->is_shared_write())
-    return id2string(id(event))+"$wclk$"+i2string(axiom);
+    return id2string(id(event))+"$wclk$"+std::to_string(axiom);
   else if(event->is_shared_read())
-    return id2string(id(event))+"$rclk$"+i2string(axiom);
+    return id2string(id(event))+"$rclk$"+std::to_string(axiom);
   else
     assert(false);
 
@@ -227,8 +226,8 @@ symbol_exprt partial_order_concurrencyt::clock(
   {
     assert(is_spawn(event));
     identifier=
-      "t"+i2string(event->source.thread_nr+1)+"$"+
-      i2string(numbering[event])+"$spwnclk$"+i2string(axiom);
+      "t"+std::to_string(event->source.thread_nr+1)+"$"+
+      std::to_string(numbering[event])+"$spwnclk$"+std::to_string(axiom);
   }
   else
     assert(false);
diff --git a/src/goto-symex/postcondition.cpp b/src/goto-symex/postcondition.cpp
index 4be55beaa65..003f0ac60a8 100644
--- a/src/goto-symex/postcondition.cpp
+++ b/src/goto-symex/postcondition.cpp
@@ -255,7 +255,7 @@ bool postconditiont::is_used(
 
     value_setst::valuest expr_set;
     value_set.get_value_set(expr.op0(), expr_set, ns);
-    hash_set_cont<irep_idt, irep_id_hash> symbols;
+    std::unordered_set<irep_idt, irep_id_hash> symbols;
 
     for(value_setst::valuest::const_iterator
         it=expr_set.begin();
diff --git a/src/goto-symex/precondition.cpp b/src/goto-symex/precondition.cpp
index d7874b9f3b8..4c392e57d94 100644
--- a/src/goto-symex/precondition.cpp
+++ b/src/goto-symex/precondition.cpp
@@ -171,7 +171,7 @@ void preconditiont::compute_rec(exprt &dest)
 
     value_setst::valuest expr_set;
     value_sets.get_values(target, dest.op0(), expr_set);
-    hash_set_cont<irep_idt, irep_id_hash> symbols;
+    std::unordered_set<irep_idt, irep_id_hash> symbols;
 
     for(value_setst::valuest::const_iterator
         it=expr_set.begin();
diff --git a/src/goto-symex/slice.cpp b/src/goto-symex/slice.cpp
index 8421e5f30b2..5e2594c656d 100644
--- a/src/goto-symex/slice.cpp
+++ b/src/goto-symex/slice.cpp
@@ -6,7 +6,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 \*******************************************************************/
 
-#include <util/hash_cont.h>
 #include <util/std_expr.h>
 
 #include "slice.h"
diff --git a/src/goto-symex/slice.h b/src/goto-symex/slice.h
index 410725b5a59..1fd15969274 100644
--- a/src/goto-symex/slice.h
+++ b/src/goto-symex/slice.h
@@ -23,7 +23,7 @@ void slice(symex_target_equationt &equation,
 
 // Collects "open" variables that are used but not assigned
 
-typedef hash_set_cont<irep_idt, irep_id_hash> symbol_sett;
+typedef std::unordered_set<irep_idt, irep_id_hash> symbol_sett;
 
 void collect_open_variables(
   const symex_target_equationt &equation,
diff --git a/src/goto-symex/slice_by_trace.cpp b/src/goto-symex/slice_by_trace.cpp
index 8928b0524d7..922f66b3eb5 100644
--- a/src/goto-symex/slice_by_trace.cpp
+++ b/src/goto-symex/slice_by_trace.cpp
@@ -13,7 +13,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <util/string2int.h>
 #include <util/simplify_expr.h>
-#include <util/i2string.h>
 #include <util/arith_tools.h>
 #include <util/std_expr.h>
 #include <util/guard.h>
@@ -611,8 +610,9 @@ std::set<exprt> symex_slice_by_tracet::implied_guards(exprt e)
 
   if (e.id() == ID_symbol)
   { // Guard or merge
-    const char* merge_loc = strstr(e.get(ID_identifier).c_str(),"merge#");
-    if(merge_loc == NULL)
+    const std::string &id_string=id2string(e.get(ID_identifier));
+    std::string::size_type merge_loc=id_string.find("merge#");
+    if(merge_loc==std::string::npos)
     {
       exprt e_copy (e);
       simplify(e_copy, ns);
@@ -621,7 +621,7 @@ std::set<exprt> symex_slice_by_tracet::implied_guards(exprt e)
     }
     else
     {
-      int i = unsafe_c_str2int(merge_loc+1);
+      int i=unsafe_string2int(id_string.substr(merge_loc+6));
       if (merge_impl_cache_back[i].first)
       {
         return merge_impl_cache_back[i].second;
diff --git a/src/goto-symex/symex_builtin_functions.cpp b/src/goto-symex/symex_builtin_functions.cpp
index 0a1fbbf8505..ed9c6262ee4 100644
--- a/src/goto-symex/symex_builtin_functions.cpp
+++ b/src/goto-symex/symex_builtin_functions.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <cassert>
 
 #include <util/expr_util.h>
-#include <util/i2string.h>
 #include <util/arith_tools.h>
 #include <util/cprover_prefix.h>
 #include <util/std_types.h>
@@ -143,7 +142,7 @@ void goto_symext::symex_malloc(
 
       symbolt size_symbol;
 
-      size_symbol.base_name="dynamic_object_size"+i2string(dynamic_counter);
+      size_symbol.base_name="dynamic_object_size"+std::to_string(dynamic_counter);
       size_symbol.name="symex_dynamic::"+id2string(size_symbol.base_name);
       size_symbol.is_lvalue=true;
       size_symbol.type=tmp_size.type();
@@ -161,7 +160,7 @@ void goto_symext::symex_malloc(
   // value
   symbolt value_symbol;
 
-  value_symbol.base_name="dynamic_object"+i2string(dynamic_counter);
+  value_symbol.base_name="dynamic_object"+std::to_string(dynamic_counter);
   value_symbol.name="symex_dynamic::"+id2string(value_symbol.base_name);
   value_symbol.is_lvalue=true;
   value_symbol.type=object_type;
@@ -249,7 +248,7 @@ void goto_symext::symex_gcc_builtin_va_arg_next(
       std::string base=id2string(function_identifier)+"::va_arg";
 
       if(has_prefix(id2string(id), base))
-        id=base+i2string(
+        id=base+std::to_string(
           safe_string2unsigned(
             std::string(id2string(id), base.size(), std::string::npos))+1);
       else
@@ -464,7 +463,7 @@ void goto_symext::symex_cpp_new(
 
   dynamic_counter++;
 
-  const std::string count_string(i2string(dynamic_counter));
+  const std::string count_string(std::to_string(dynamic_counter));
 
   // value
   symbolt symbol;
diff --git a/src/goto-symex/symex_function_call.cpp b/src/goto-symex/symex_function_call.cpp
index c2d5d30ebd9..16574d5679f 100644
--- a/src/goto-symex/symex_function_call.cpp
+++ b/src/goto-symex/symex_function_call.cpp
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <cassert>
 
 #include <util/expr_util.h>
-#include <util/i2string.h>
 #include <util/cprover_prefix.h>
 #include <util/prefix.h>
 #include <util/arith_tools.h>
@@ -161,18 +160,18 @@ void goto_symext::parameter_assignments(
     // These are va_arg arguments; their types may differ from call to call
     unsigned va_count=0;
     const symbolt *va_sym=0;
-    while(!ns.lookup(id2string(function_identifier)+"::va_arg"+i2string(va_count),
+    while(!ns.lookup(id2string(function_identifier)+"::va_arg"+std::to_string(va_count),
                     va_sym))
       ++va_count;
 
     for( ; it1!=arguments.end(); it1++, va_count++)
     {
-      irep_idt id=id2string(function_identifier)+"::va_arg"+i2string(va_count);
+      irep_idt id=id2string(function_identifier)+"::va_arg"+std::to_string(va_count);
 
       // add to symbol table
       symbolt symbol;
       symbol.name=id;
-      symbol.base_name="va_arg"+i2string(va_count);
+      symbol.base_name="va_arg"+std::to_string(va_count);
       symbol.type=it1->type();
 
       new_symbol_table.move(symbol);
diff --git a/src/goto-symex/symex_goto.cpp b/src/goto-symex/symex_goto.cpp
index cb808b729e2..17149677965 100644
--- a/src/goto-symex/symex_goto.cpp
+++ b/src/goto-symex/symex_goto.cpp
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <util/expr_util.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 
 #include "goto_symex.h"
 
@@ -297,12 +296,12 @@ void goto_symext::phi_function(
   statet &dest_state)
 {
   // go over all variables to see what changed
-  hash_set_cont<ssa_exprt, irep_hash> variables;
+  std::unordered_set<ssa_exprt, irep_hash> variables;
 
   goto_state.level2_get_variables(variables);
   dest_state.level2.get_variables(variables);
 
-  for(hash_set_cont<ssa_exprt, irep_hash>::const_iterator
+  for(std::unordered_set<ssa_exprt, irep_hash>::const_iterator
       it=variables.begin();
       it!=variables.end();
       it++)
@@ -333,7 +332,7 @@ void goto_symext::phi_function(
     // only later be removed from level2.current_names by pop_frame
     // once the thread is executed)
     if(!it->get_level_0().empty() &&
-       it->get_level_0()!=i2string(dest_state.source.thread_nr))
+       it->get_level_0()!=std::to_string(dest_state.source.thread_nr))
       continue;
 
     exprt goto_state_rhs=*it, dest_state_rhs=*it;
@@ -427,7 +426,7 @@ void goto_symext::loop_bound_exceeded(
     {
       // Generate VCC for unwinding assertion.
       vcc(negated_cond,
-          "unwinding assertion loop "+i2string(loop_number),
+          "unwinding assertion loop "+std::to_string(loop_number),
           state);
 
       // add to state guard to prevent further assignments
diff --git a/src/goto-symex/symex_target_equation.cpp b/src/goto-symex/symex_target_equation.cpp
index 2f6051177d4..8c4e48f8a2e 100644
--- a/src/goto-symex/symex_target_equation.cpp
+++ b/src/goto-symex/symex_target_equation.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
-#include <util/i2string.h>
 #include <util/std_expr.h>
 #include <util/expr_util.h>
 
@@ -894,7 +893,7 @@ void symex_target_equationt::convert_io(
         {
           symbol_exprt symbol;
           symbol.type()=tmp.type();
-          symbol.set_identifier("symex::io::"+i2string(io_count++));
+          symbol.set_identifier("symex::io::"+std::to_string(io_count++));
 
           equal_exprt eq(tmp, symbol);
           merge_irep(eq);
diff --git a/src/java_bytecode/expr2java.cpp b/src/java_bytecode/expr2java.cpp
index 14b033a68fe..10476044889 100644
--- a/src/java_bytecode/expr2java.cpp
+++ b/src/java_bytecode/expr2java.cpp
@@ -8,12 +8,13 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 #include <cassert>
 
+#include <util/namespace.h>
 #include <util/std_types.h>
 #include <util/std_expr.h>
 #include <util/symbol.h>
-#include <util/hash_cont.h>
 #include <util/arith_tools.h>
 
+#include <ansi-c/c_qualifiers.h>
 #include <ansi-c/expr2c_class.h>
 
 #include "java_types.h"
@@ -50,7 +51,7 @@ class expr2javat:public expr2ct
     const c_qualifierst &qualifiers,
     const std::string &declarator);
 
-  typedef hash_set_cont<std::string, string_hash> id_sett;
+  typedef std::unordered_set<std::string, string_hash> id_sett;
 };
 
 /*******************************************************************\
diff --git a/src/java_bytecode/java_bytecode_convert_method.cpp b/src/java_bytecode/java_bytecode_convert_method.cpp
index 4fd33ae121a..c4a91cff14f 100644
--- a/src/java_bytecode/java_bytecode_convert_method.cpp
+++ b/src/java_bytecode/java_bytecode_convert_method.cpp
@@ -15,7 +15,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/std_expr.h>
 #include <util/expanding_vector.h>
 #include <util/string2int.h>
-#include <util/i2string.h>
 #include <util/prefix.h>
 #include <util/arith_tools.h>
 #include <util/ieee_float.h>
@@ -156,7 +155,7 @@ class java_bytecode_convert_methodt:public messaget
 
   symbol_exprt tmp_variable(const std::string &prefix, const typet &type)
   {
-    irep_idt base_name=prefix+"_tmp"+i2string(tmp_vars.size());
+    irep_idt base_name=prefix+"_tmp"+std::to_string(tmp_vars.size());
     irep_idt identifier=id2string(current_method)+"::"+id2string(base_name);
 
     auxiliary_symbolt tmp_symbol;
@@ -346,7 +345,7 @@ void java_bytecode_convert_methodt::convert(
       {
         const typet &type=parameters[i].type();
         char suffix=java_char_from_type(type);
-        base_name="arg"+i2string(param_index)+suffix;
+        base_name="arg"+std::to_string(param_index)+suffix;
         identifier=id2string(method_identifier)+"::"+id2string(base_name);
       }
 
@@ -1525,7 +1524,7 @@ codet java_bytecode_convert_methodt::convert_instructions(
     const codet &c=it.second.code;
 
     if(targets.find(address)!=targets.end())
-      code.add(code_labelt(label(i2string(address)), c));
+      code.add(code_labelt(label(std::to_string(address)), c));
     else if(c.get_statement()!=ID_skip)
       code.add(c);
   }
diff --git a/src/java_bytecode/java_bytecode_parser.cpp b/src/java_bytecode/java_bytecode_parser.cpp
index 449e5954295..45cbffa1035 100644
--- a/src/java_bytecode/java_bytecode_parser.cpp
+++ b/src/java_bytecode/java_bytecode_parser.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <fstream>
 #include <map>
 
-#include <util/i2string.h>
 #include <util/parser.h>
 #include <util/std_expr.h>
 #include <util/arith_tools.h>
diff --git a/src/java_bytecode/java_entry_point.cpp b/src/java_bytecode/java_entry_point.cpp
index 96bbd5764bb..19f195cf007 100644
--- a/src/java_bytecode/java_entry_point.cpp
+++ b/src/java_bytecode/java_entry_point.cpp
@@ -20,7 +20,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/config.h>
 #include <util/namespace.h>
 #include <util/pointer_offset_size.h>
-#include <util/i2string.h>
 #include <util/prefix.h>
 #include <ansi-c/c_types.h>
 #include <ansi-c/string_constant.h>
diff --git a/src/java_bytecode/java_object_factory.cpp b/src/java_bytecode/java_object_factory.cpp
index 854c086df04..15735f62539 100644
--- a/src/java_bytecode/java_object_factory.cpp
+++ b/src/java_bytecode/java_object_factory.cpp
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/std_types.h>
 #include <util/std_code.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/namespace.h>
 #include <util/expr_util.h>
 
@@ -192,7 +191,7 @@ symbolt &new_tmp_symbol(symbol_tablet &symbol_table)
 
   do
   {
-    new_symbol.name="tmp_object_factory$"+i2string(++temporary_counter);
+    new_symbol.name="tmp_object_factory$"+std::to_string(++temporary_counter);
     new_symbol.base_name=new_symbol.name;
     new_symbol.mode=ID_java;
   } while(symbol_table.move(new_symbol, symbol_ptr));
diff --git a/src/jsil/jsil_typecheck.h b/src/jsil/jsil_typecheck.h
index c8fa8c1a3b1..f515147a297 100644
--- a/src/jsil/jsil_typecheck.h
+++ b/src/jsil/jsil_typecheck.h
@@ -9,6 +9,8 @@ Author: Michael Tautschnig, tautschn@amazon.com
 #ifndef CPROVER_JSIL_JSIL_TYPECHECK_H
 #define CPROVER_JSIL_JSIL_TYPECHECK_H
 
+#include <unordered_set>
+
 #include <util/typecheck.h>
 #include <util/namespace.h>
 #include <util/std_code.h>
@@ -89,7 +91,7 @@ class jsil_typecheckt:public typecheckt
   virtual std::string to_string(const exprt &expr);
   virtual std::string to_string(const typet &type);
 
-  hash_set_cont<irep_idt, irep_id_hash> already_typechecked;
+  std::unordered_set<irep_idt, irep_id_hash> already_typechecked;
 };
 
 #endif // CPROVER_JSIL_JSIL_TYPECHECK_H
diff --git a/src/langapi/language_ui.cpp b/src/langapi/language_ui.cpp
index c0876c3faed..d409dc1947e 100644
--- a/src/langapi/language_ui.cpp
+++ b/src/langapi/language_ui.cpp
@@ -10,7 +10,6 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 #include <memory>
 #include <iostream>
 
-#include <util/i2string.h>
 #include <util/namespace.h>
 #include <util/language.h>
 #include <util/cmdline.h>
diff --git a/src/linking/linking.cpp b/src/linking/linking.cpp
index 90a578cc331..3ff4d09de22 100644
--- a/src/linking/linking.cpp
+++ b/src/linking/linking.cpp
@@ -12,7 +12,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/find_symbols.h>
 #include <util/source_location.h>
 #include <util/base_type.h>
-#include <util/i2string.h>
 #include <util/std_expr.h>
 #include <util/std_types.h>
 #include <util/simplify_expr.h>
@@ -222,8 +221,8 @@ void linkingt::detailed_conflict_report_rec(
     if(components1.size()!=components2.size())
     {
       msg="number of members is different (";
-      msg+=i2string(components1.size())+'/';
-      msg+=i2string(components2.size())+')';
+      msg+=std::to_string(components1.size())+'/';
+      msg+=std::to_string(components2.size())+')';
     }
     else
       for(std::size_t i=0; i<components1.size(); ++i)
@@ -233,14 +232,14 @@ void linkingt::detailed_conflict_report_rec(
 
         if(components1[i].get_name()!=components2[i].get_name())
         {
-          msg="names of member "+i2string(i)+" differ (";
+          msg="names of member "+std::to_string(i)+" differ (";
           msg+=id2string(components1[i].get_name())+'/';
           msg+=id2string(components2[i].get_name())+')';
           break;
         }
         else if(!base_type_eq(subtype1, subtype2, ns))
         {
-          typedef hash_set_cont<typet, irep_hash> type_sett;
+          typedef std::unordered_set<typet, irep_hash> type_sett;
           type_sett parent_types;
 
           exprt e=conflict_path_before;
@@ -310,22 +309,22 @@ void linkingt::detailed_conflict_report_rec(
     else if(members1.size()!=members2.size())
     {
       msg="number of enum members is different (";
-      msg+=i2string(members1.size())+'/';
-      msg+=i2string(members2.size())+')';
+      msg+=std::to_string(members1.size())+'/';
+      msg+=std::to_string(members2.size())+')';
     }
     else
       for(std::size_t i=0; i<members1.size(); ++i)
       {
         if(members1[i].get_base_name()!=members2[i].get_base_name())
         {
-          msg="names of member "+i2string(i)+" differ (";
+          msg="names of member "+std::to_string(i)+" differ (";
           msg+=id2string(members1[i].get_base_name())+'/';
           msg+=id2string(members2[i].get_base_name())+')';
           break;
         }
         else if(members1[i].get_value()!=members2[i].get_value())
         {
-          msg="values of member "+i2string(i)+" differ (";
+          msg="values of member "+std::to_string(i)+" differ (";
           msg+=id2string(members1[i].get_value())+'/';
           msg+=id2string(members2[i].get_value())+')';
           break;
@@ -350,14 +349,14 @@ void linkingt::detailed_conflict_report_rec(
     if(parameters1.size()!=parameters2.size())
     {
       msg="parameter counts differ (";
-      msg+=i2string(parameters1.size())+'/';
-      msg+=i2string(parameters2.size())+')';
+      msg+=std::to_string(parameters1.size())+'/';
+      msg+=std::to_string(parameters2.size())+')';
     }
     else if(!base_type_eq(return_type1, return_type2, ns))
     {
       conflict_path=
         index_exprt(conflict_path,
-                    constant_exprt(i2string(-1), integer_typet()));
+                    constant_exprt(std::to_string(-1), integer_typet()));
 
       if(depth>0)
         detailed_conflict_report_rec(
@@ -380,7 +379,7 @@ void linkingt::detailed_conflict_report_rec(
         {
           conflict_path=
             index_exprt(conflict_path,
-                        constant_exprt(i2string(i), integer_typet()));
+                        constant_exprt(std::to_string(i), integer_typet()));
 
           if(depth>0)
             detailed_conflict_report_rec(
@@ -498,7 +497,7 @@ irep_idt linkingt::rename(const irep_idt id)
   while(true)
   {
     irep_idt new_identifier=
-      id2string(id)+"$link"+i2string(++cnt);
+      id2string(id)+"$link"+std::to_string(++cnt);
 
     if(main_symbol_table.symbols.find(new_identifier)!=
        main_symbol_table.symbols.end())
diff --git a/src/linking/linking_class.h b/src/linking/linking_class.h
index c40ce92530c..fa14f520330 100644
--- a/src/linking/linking_class.h
+++ b/src/linking/linking_class.h
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <util/namespace.h>
 #include <util/rename_symbol.h>
-#include <util/hash_cont.h>
 #include <util/typecheck.h>
 #include <util/std_expr.h>
 
@@ -35,7 +34,7 @@ class linkingt:public typecheckt
 
 protected:
 
-  typedef hash_set_cont<irep_idt, irep_id_hash> id_sett;
+  typedef std::unordered_set<irep_idt, irep_id_hash> id_sett;
 
   bool needs_renaming_type(
     const symbolt &old_symbol,
@@ -170,7 +169,7 @@ class linkingt:public typecheckt
   namespacet ns;
 
   // X -> Y iff Y uses X for new symbol type IDs X and Y
-  typedef hash_map_cont<irep_idt, id_sett, irep_id_hash> used_byt;
+  typedef std::unordered_map<irep_idt, id_sett, irep_id_hash> used_byt;
 
   irep_idt rename(irep_idt);
 
diff --git a/src/musketeer/fence_inserter.cpp b/src/musketeer/fence_inserter.cpp
index c939285537f..3ec27b597f0 100644
--- a/src/musketeer/fence_inserter.cpp
+++ b/src/musketeer/fence_inserter.cpp
@@ -6,7 +6,6 @@ Author: Vincent Nimal
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/graph.h>
 
 #include <sstream>
@@ -287,14 +286,14 @@ void inline fence_insertert::mip_set_var(ilpt& ilp,
 
     if(model==Power || model==Unknown) {
       /* dp variable for e */
-      const std::string name_dp="dp_"+i2string(i);
+      const std::string name_dp="dp_"+std::to_string(i);
       glp_set_col_name(ilp.lp, i, name_dp.c_str());
       glp_set_col_bnds(ilp.lp, i, GLP_LO, 0.0, 0.0);
       glp_set_obj_coef(ilp.lp, i, (has_cost?fence_cost(Dp):0)*freq_sum);
       glp_set_col_kind(ilp.lp, i, GLP_BV);
 
       /* fence variable for e */
-      const std::string name_f="f_"+i2string(i);
+      const std::string name_f="f_"+std::to_string(i);
       glp_set_col_name(ilp.lp, i+1, name_f.c_str());
       glp_set_col_bnds(ilp.lp, i+1, GLP_LO, 0.0, 0.0);
       glp_set_obj_coef(ilp.lp, i+1, (has_cost?fence_cost(Fence):0)*freq_sum);
@@ -303,14 +302,14 @@ void inline fence_insertert::mip_set_var(ilpt& ilp,
 // Note: uncomment for br and cf fences
 #if 0
       /* br variable for e */
-      const std::string name_br="br_"+i2string(i);
+      const std::string name_br="br_"+std::to_string(i);
       glp_set_col_name(ilp.lp, i+2, name_br.c_str());
       glp_set_col_bnds(ilp.lp, i+2, GLP_LO, 0.0, 0.0);
       glp_set_obj_coef(ilp.lp, i+2, (has_cost?fence_cost(Branching):0)*freq_sum);
       glp_set_col_kind(ilp.lp, i+2, GLP_BV);
 
       /* cf variable for e */
-      const std::string name_cf="cf_"+i2string(i);
+      const std::string name_cf="cf_"+std::to_string(i);
       glp_set_col_name(ilp.lp, i+3, name_cf.c_str());
       glp_set_col_bnds(ilp.lp, i+3, GLP_LO, 0.0, 0.0);
       glp_set_obj_coef(ilp.lp, i+3, (has_cost?fence_cost(Ctlfence):0)*freq_sum);
@@ -319,7 +318,7 @@ void inline fence_insertert::mip_set_var(ilpt& ilp,
 
       if(model==Power) {
         /* lwf variable for e */
-        const std::string name_lwf="lwf_"+i2string(i);
+        const std::string name_lwf="lwf_"+std::to_string(i);
         glp_set_col_name(ilp.lp, i+2/*4*/, name_lwf.c_str());
         glp_set_col_bnds(ilp.lp, i+2/*4*/, GLP_LO, 0.0, 0.0);
         glp_set_obj_coef(ilp.lp, i+2/*4*/,
@@ -329,7 +328,7 @@ void inline fence_insertert::mip_set_var(ilpt& ilp,
     }
     else {
       /* fence variable for e */
-      const std::string name_f="f_"+i2string(i);
+      const std::string name_f="f_"+std::to_string(i);
       glp_set_col_name(ilp.lp, i, name_f.c_str());
       glp_set_col_bnds(ilp.lp, i, GLP_LO, 0.0, 0.0);
       glp_set_obj_coef(ilp.lp, i, (has_cost?fence_cost(Fence):0)*freq_sum);
@@ -370,7 +369,7 @@ void inline fence_insertert::mip_set_cst(ilpt& ilp, unsigned& i)
     /* for all e */
     for(unsigned j=1; j<=c_wr_it->size(); ++j)
     {
-      std::string name="C_"+i2string(i)+"_c_wr_"+i2string(j);
+      std::string name="C_"+std::to_string(i)+"_c_wr_"+std::to_string(j);
       glp_set_row_name(ilp.lp, i, name.c_str());
       glp_set_row_bnds(ilp.lp, i, GLP_LO, 1.0, 0.0); /* >= 1*/
       ++i;
@@ -387,7 +386,7 @@ void inline fence_insertert::mip_set_cst(ilpt& ilp, unsigned& i)
     /* for all e */
     for(unsigned j=1; j<=c_ww_it->size(); ++j)
     {
-      std::string name="C_"+i2string(i)+"_c_ww_"+i2string(j);
+      std::string name="C_"+std::to_string(i)+"_c_ww_"+std::to_string(j);
       glp_set_row_name(ilp.lp, i, name.c_str());
       glp_set_row_bnds(ilp.lp, i, GLP_LO, 1.0, 0.0); /* >= 1*/
       ++i;
@@ -404,7 +403,7 @@ void inline fence_insertert::mip_set_cst(ilpt& ilp, unsigned& i)
     /* for all e */
     for(unsigned j=1; j<=c_rw_it->size(); ++j)
     {
-      std::string name="C_"+i2string(i)+"_c_rw_"+i2string(j);
+      std::string name="C_"+std::to_string(i)+"_c_rw_"+std::to_string(j);
       glp_set_row_name(ilp.lp, i, name.c_str());
       glp_set_row_bnds(ilp.lp, i, GLP_LO, 1.0, 0.0); /* >= 1*/
       ++i;
@@ -421,7 +420,7 @@ void inline fence_insertert::mip_set_cst(ilpt& ilp, unsigned& i)
     /* for all e */
     for(unsigned j=1; j<=c_rr_it->size(); ++j)
     {
-      std::string name="C_"+i2string(i)+"_c_rr_"+i2string(j);
+      std::string name="C_"+std::to_string(i)+"_c_rr_"+std::to_string(j);
       glp_set_row_name(ilp.lp, i, name.c_str());
       glp_set_row_bnds(ilp.lp, i, GLP_LO, 1.0, 0.0); /* >= 1*/
       ++i;
@@ -438,7 +437,7 @@ void inline fence_insertert::mip_set_cst(ilpt& ilp, unsigned& i)
       /* for all e */
       for(unsigned j=1; j<=c_it->size(); ++j)
       {
-        std::string name="C_"+i2string(i)+"_c_"+i2string(j);
+        std::string name="C_"+std::to_string(i)+"_c_"+std::to_string(j);
         glp_set_row_name(ilp.lp, i, name.c_str());
         glp_set_row_bnds(ilp.lp, i, GLP_LO, 1.0, 0.0); /* >= 1*/
         ++i;
diff --git a/src/musketeer/fence_shared.cpp b/src/musketeer/fence_shared.cpp
index f4f95501472..c3557d712af 100644
--- a/src/musketeer/fence_shared.cpp
+++ b/src/musketeer/fence_shared.cpp
@@ -13,7 +13,6 @@ Author: Vincent Nimal
 #include <vector>
 #include <set>
 
-#include <util/i2string.h>
 #include <util/cprover_prefix.h>
 #include <util/expr_util.h>
 #include <util/prefix.h>
diff --git a/src/musketeer/fencer.cpp b/src/musketeer/fencer.cpp
index a372355dc08..bbcb1db1d2d 100644
--- a/src/musketeer/fencer.cpp
+++ b/src/musketeer/fencer.cpp
@@ -6,7 +6,6 @@ Author: Vincent Nimal
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/cprover_prefix.h>
 #include <util/expr_util.h>
 #include <util/message.h>
diff --git a/src/musketeer/pensieve.cpp b/src/musketeer/pensieve.cpp
index f28d8eccfc0..42ae7b61a49 100644
--- a/src/musketeer/pensieve.cpp
+++ b/src/musketeer/pensieve.cpp
@@ -6,7 +6,6 @@ Author: Vincent Nimal
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/cprover_prefix.h>
 #include <util/expr_util.h>
 #include <util/namespace.h>
diff --git a/src/musketeer/propagate_const_function_pointers.cpp b/src/musketeer/propagate_const_function_pointers.cpp
index ec6597d2bfa..253d601a056 100644
--- a/src/musketeer/propagate_const_function_pointers.cpp
+++ b/src/musketeer/propagate_const_function_pointers.cpp
@@ -2,8 +2,6 @@
 #include <util/std_expr.h>
 #include <util/std_types.h>
 #include <util/irep.h>
-#include <util/hash_cont.h>
-#include <util/i2string.h>
 #include <util/namespace.h>
 #include <util/message.h>
 
@@ -21,16 +19,16 @@ class const_function_pointer_propagationt {
   const namespacet ns;
   messaget& message;
 
-  hash_map_cont<irep_idt, unsigned, irep_id_hash> map_unique;
+  std::unordered_map<irep_idt, unsigned, irep_id_hash> map_unique;
 
   /* maps const pointer to function (expression + arguments at call)  */
-  hash_map_cont<irep_idt, symbol_exprt, irep_id_hash> pointer_to_fun;
+  std::unordered_map<irep_idt, symbol_exprt, irep_id_hash> pointer_to_fun;
 
   /* maps const pointer to where it was defined in the call function stack */
-  hash_map_cont<irep_idt, unsigned, irep_id_hash> pointer_to_stack;
+  std::unordered_map<irep_idt, unsigned, irep_id_hash> pointer_to_stack;
 
   /* where a const function to inline was the first time invoked */
-  hash_map_cont<irep_idt, unsigned, irep_id_hash> fun_id_to_invok;
+  std::unordered_map<irep_idt, unsigned, irep_id_hash> fun_id_to_invok;
 
   /* stack of callsites: provides functions and location in the goto-program */
   goto_programt::const_targetst callsite_stack;
@@ -176,12 +174,12 @@ void const_function_pointer_propagationt::dup_caller_and_inline_callee(
     {
       /* unique suffix */
       if(map_unique.find(function_id)!=map_unique.end()) {
-        suffix+=i2string(map_unique[function_id]);
+        suffix+=std::to_string(map_unique[function_id]);
         ++map_unique[function_id];
       }
       else {
         map_unique[function_id]=0;
-        suffix+=i2string(map_unique[function_id]);
+        suffix+=std::to_string(map_unique[function_id]);
         ++map_unique[function_id];
       }
 
@@ -366,7 +364,7 @@ void const_function_pointer_propagationt::arg_stackt::add_args(
         //cfpp.symbol_table.lookup(arg_symbol_expr.get_identifier());
 
       // debug
-      for(hash_map_cont<irep_idt, unsigned, irep_id_hash>::const_iterator
+      for(std::unordered_map<irep_idt, unsigned, irep_id_hash>::const_iterator
         it=cfpp.fun_id_to_invok.begin();
         it!=cfpp.fun_id_to_invok.end();
         ++it)
diff --git a/src/path-symex/locs.h b/src/path-symex/locs.h
index 5978fae2d01..f45349b420d 100644
--- a/src/path-symex/locs.h
+++ b/src/path-symex/locs.h
@@ -109,12 +109,4 @@ class target_to_loc_mapt
   mapt map;
 };
 
-#define forall_locs(it, locs) \
-  for(locst::loc_vectort::const_iterator it=(locs).loc_vector.begin(); \
-      it!=(locs).loc_vector.end(); it++)
-
-#define Forall_locs(it, locs) \
-  for(exprt::operandst::iterator it=(expr).loc_vector.begin(); \
-      it!=(locs).loc_vector.end(); it++)
-
 #endif // CPROVER_PATH_SYMEX_LOCS_H
diff --git a/src/path-symex/path_symex.cpp b/src/path-symex/path_symex.cpp
index 45fb7bb9e5a..d1f1f411f3a 100644
--- a/src/path-symex/path_symex.cpp
+++ b/src/path-symex/path_symex.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/arith_tools.h>
 #include <util/simplify_expr.h>
 #include <util/byte_operators.h>
-#include <util/i2string.h>
 #include <util/pointer_offset_size.h>
 #include <util/expr_util.h>
 #include <util/base_type.h>
@@ -240,7 +239,7 @@ void path_symext::symex_malloc(
 
       symbolt size_symbol;
 
-      size_symbol.base_name="dynamic_object_size"+i2string(dynamic_count);
+      size_symbol.base_name="dynamic_object_size"+std::to_string(dynamic_count);
       size_symbol.name="symex::"+id2string(size_symbol.base_name);
       size_symbol.is_lvalue=true;
       size_symbol.type=tmp_size.type();
@@ -259,7 +258,7 @@ void path_symext::symex_malloc(
   // value
   symbolt value_symbol;
 
-  value_symbol.base_name="dynamic_object"+i2string(state.var_map.dynamic_count);
+  value_symbol.base_name="dynamic_object"+std::to_string(state.var_map.dynamic_count);
   value_symbol.name="symex_dynamic::"+id2string(value_symbol.base_name);
   value_symbol.is_lvalue=true;
   value_symbol.type=object_type;
diff --git a/src/path-symex/path_symex_state.cpp b/src/path-symex/path_symex_state.cpp
index 5e9886a0368..3cd0cd0d269 100644
--- a/src/path-symex/path_symex_state.cpp
+++ b/src/path-symex/path_symex_state.cpp
@@ -10,7 +10,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/arith_tools.h>
 #include <util/expr_util.h>
 #include <util/decision_procedure.h>
-#include <util/i2string.h>
 
 #include <ansi-c/c_types.h>
 
diff --git a/src/path-symex/path_symex_state_read.cpp b/src/path-symex/path_symex_state_read.cpp
index c527e383d3b..33aab3c5fc5 100644
--- a/src/path-symex/path_symex_state_read.cpp
+++ b/src/path-symex/path_symex_state_read.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <util/simplify_expr.h>
 #include <util/arith_tools.h>
-#include <util/i2string.h>
 
 #include <pointer-analysis/dereference.h>
 
@@ -305,7 +304,7 @@ exprt path_symex_statet::instantiate_rec(
 
     if(statement==ID_nondet)
     {
-      irep_idt id="symex::nondet"+i2string(var_map.nondet_count);
+      irep_idt id="symex::nondet"+std::to_string(var_map.nondet_count);
       var_map.nondet_count++;
       return symbol_exprt(id, src.type());
     }
diff --git a/src/path-symex/var_map.cpp b/src/path-symex/var_map.cpp
index e408909df12..984d1049abc 100644
--- a/src/path-symex/var_map.cpp
+++ b/src/path-symex/var_map.cpp
@@ -10,7 +10,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <util/symbol.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/prefix.h>
 
 #include "var_map.h"
@@ -156,7 +155,7 @@ Function: var_mapt::var_infot::ssa_identifier
 irep_idt var_mapt::var_infot::ssa_identifier() const
 {
   return id2string(full_identifier)+
-         "#"+i2string(ssa_counter);
+         "#"+std::to_string(ssa_counter);
 }
 
 /*******************************************************************\
diff --git a/src/pointer-analysis/object_numbering.h b/src/pointer-analysis/object_numbering.h
index 714f3190252..beddfb76ab6 100644
--- a/src/pointer-analysis/object_numbering.h
+++ b/src/pointer-analysis/object_numbering.h
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_POINTER_ANALYSIS_OBJECT_NUMBERING_H
 #define CPROVER_POINTER_ANALYSIS_OBJECT_NUMBERING_H
 
-#include <util/hash_cont.h>
 #include <util/expr.h>
 #include <util/numbering.h>
 
diff --git a/src/pointer-analysis/value_set.cpp b/src/pointer-analysis/value_set.cpp
index 08330f06078..500dbd23bcf 100644
--- a/src/pointer-analysis/value_set.cpp
+++ b/src/pointer-analysis/value_set.cpp
@@ -14,7 +14,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/expr_util.h>
 #include <util/base_type.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/prefix.h>
 #include <util/std_code.h>
 #include <util/arith_tools.h>
@@ -1619,7 +1618,7 @@ void value_sett::do_function_call(
 
   for(unsigned i=0; i<arguments.size(); i++)
   {
-    const std::string identifier="value_set::dummy_arg_"+i2string(i);
+    const std::string identifier="value_set::dummy_arg_"+std::to_string(i);
     exprt dummy_lhs=symbol_exprt(identifier, arguments[i].type());
     assign(dummy_lhs, arguments[i], ns, false, false);
   }
@@ -1637,7 +1636,7 @@ void value_sett::do_function_call(
     if(identifier=="") continue;
 
     const exprt v_expr=
-      symbol_exprt("value_set::dummy_arg_"+i2string(i), it->type());
+      symbol_exprt("value_set::dummy_arg_"+std::to_string(i), it->type());
 
     exprt actual_lhs=symbol_exprt(identifier, it->type());
     assign(actual_lhs, v_expr, ns, true, true);
diff --git a/src/pointer-analysis/value_set.h b/src/pointer-analysis/value_set.h
index 7902fc04fb8..70b7f15d698 100644
--- a/src/pointer-analysis/value_set.h
+++ b/src/pointer-analysis/value_set.h
@@ -115,7 +115,7 @@ class value_sett
   #ifdef USE_DSTRING
   typedef std::map<idt, entryt> valuest;
   #else
-  typedef hash_map_cont<idt, entryt, string_hash> valuest;
+  typedef std::unordered_map<idt, entryt, string_hash> valuest;
   #endif
 
   void get_value_set(
diff --git a/src/pointer-analysis/value_set_analysis_fi.cpp b/src/pointer-analysis/value_set_analysis_fi.cpp
index 17e28ee8b41..cba409fa8f5 100644
--- a/src/pointer-analysis/value_set_analysis_fi.cpp
+++ b/src/pointer-analysis/value_set_analysis_fi.cpp
@@ -80,7 +80,7 @@ void value_set_analysis_fit::add_vars(
   goto_program.get_decl_identifiers(locals);
 
   // cache the list for the locals to speed things up
-  typedef hash_map_cont<irep_idt, entry_listt, irep_id_hash> entry_cachet;
+  typedef std::unordered_map<irep_idt, entry_listt, irep_id_hash> entry_cachet;
   entry_cachet entry_cache;
 
   value_set_fit &v=state.value_set;
diff --git a/src/pointer-analysis/value_set_analysis_fivr.cpp b/src/pointer-analysis/value_set_analysis_fivr.cpp
index e864606ed5c..3ed0538bb1c 100644
--- a/src/pointer-analysis/value_set_analysis_fivr.cpp
+++ b/src/pointer-analysis/value_set_analysis_fivr.cpp
@@ -80,7 +80,7 @@ void value_set_analysis_fivrt::add_vars(
   goto_program.get_decl_identifiers(locals);
 
   // cache the list for the locals to speed things up
-  typedef hash_map_cont<irep_idt, entry_listt, irep_id_hash> entry_cachet;
+  typedef std::unordered_map<irep_idt, entry_listt, irep_id_hash> entry_cachet;
   entry_cachet entry_cache;
 
   value_set_fivrt &v=state.value_set;
diff --git a/src/pointer-analysis/value_set_analysis_fivrns.cpp b/src/pointer-analysis/value_set_analysis_fivrns.cpp
index 865b1a3e247..4fbe598ae13 100644
--- a/src/pointer-analysis/value_set_analysis_fivrns.cpp
+++ b/src/pointer-analysis/value_set_analysis_fivrns.cpp
@@ -80,7 +80,7 @@ void value_set_analysis_fivrnst::add_vars(
   goto_program.get_decl_identifiers(locals);
 
   // cache the list for the locals to speed things up
-  typedef hash_map_cont<irep_idt, entry_listt, irep_id_hash> entry_cachet;
+  typedef std::unordered_map<irep_idt, entry_listt, irep_id_hash> entry_cachet;
   entry_cachet entry_cache;
 
   value_set_fivrnst &v=state.value_set;
diff --git a/src/pointer-analysis/value_set_dereference.cpp b/src/pointer-analysis/value_set_dereference.cpp
index 57c6b3682fd..e19110a1c93 100644
--- a/src/pointer-analysis/value_set_dereference.cpp
+++ b/src/pointer-analysis/value_set_dereference.cpp
@@ -17,11 +17,9 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <util/string2int.h>
 #include <util/expr_util.h>
-#include <util/c_misc.h>
 #include <util/base_type.h>
 #include <util/arith_tools.h>
 #include <util/rename.h>
-#include <util/i2string.h>
 #include <util/array_name.h>
 #include <util/config.h>
 #include <util/std_expr.h>
@@ -199,7 +197,7 @@ exprt value_set_dereferencet::dereference(
       // else: produce new symbol
 
       symbolt symbol;
-      symbol.name="symex::invalid_object"+i2string(invalid_counter++);
+      symbol.name="symex::invalid_object"+std::to_string(invalid_counter++);
       symbol.base_name="invalid_object";
       symbol.type=type;
 
diff --git a/src/pointer-analysis/value_set_dereference.h b/src/pointer-analysis/value_set_dereference.h
index 5fc40f6fe25..60daefd8d4d 100644
--- a/src/pointer-analysis/value_set_dereference.h
+++ b/src/pointer-analysis/value_set_dereference.h
@@ -9,10 +9,8 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_POINTER_ANALYSIS_VALUE_SET_DEREFERENCE_H
 #define CPROVER_POINTER_ANALYSIS_VALUE_SET_DEREFERENCE_H
 
-#include <set>
-#include <string>
+#include <unordered_set>
 
-#include <util/hash_cont.h>
 #include <util/std_expr.h>
 
 #include "dereference_callback.h"
@@ -73,7 +71,7 @@ class value_set_dereferencet
   */
   static bool has_dereference(const exprt &expr);
 
-  typedef hash_set_cont<exprt, irep_hash> expr_sett;
+  typedef std::unordered_set<exprt, irep_hash> expr_sett;
 
 private:
   const namespacet &ns;
diff --git a/src/pointer-analysis/value_set_fi.cpp b/src/pointer-analysis/value_set_fi.cpp
index d758e40c987..e1157b49324 100644
--- a/src/pointer-analysis/value_set_fi.cpp
+++ b/src/pointer-analysis/value_set_fi.cpp
@@ -14,7 +14,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/expr_util.h>
 #include <util/base_type.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/prefix.h>
 #include <util/std_code.h>
 #include <util/arith_tools.h>
@@ -1565,7 +1564,7 @@ void value_set_fit::do_function_call(
   for(unsigned i=0; i<arguments.size(); i++)
   {
     const std::string identifier="value_set::" + id2string(function) + "::" +
-                                 "argument$"+i2string(i);
+                                 "argument$"+std::to_string(i);
     add_var(identifier, "");
     exprt dummy_lhs=symbol_exprt(identifier, arguments[i].type());
     assign(dummy_lhs, arguments[i], ns);
@@ -1587,7 +1586,7 @@ void value_set_fit::do_function_call(
 
     const exprt v_expr=
       symbol_exprt("value_set::" + id2string(function) + "::" +
-                   "argument$"+i2string(i), it->type());
+                   "argument$"+std::to_string(i), it->type());
 
     exprt actual_lhs=symbol_exprt(identifier, it->type());
     assign(actual_lhs, v_expr, ns);
@@ -1613,7 +1612,7 @@ void value_set_fit::do_end_function(
 {
   if(lhs.is_nil()) return;
 
-  std::string rvs = "value_set::return_value" + i2string(from_function);
+  std::string rvs = "value_set::return_value" + std::to_string(from_function);
   symbol_exprt rhs(rvs, lhs.type());
 
   assign(lhs, rhs, ns);
@@ -1711,7 +1710,7 @@ void value_set_fit::apply_code(
     // this is turned into an assignment
     if(code.operands().size()==1)
     {
-      std::string rvs = "value_set::return_value" + i2string(from_function);
+      std::string rvs = "value_set::return_value" + std::to_string(from_function);
       symbol_exprt lhs(rvs, code.op0().type());
       assign(lhs, code.op0(), ns);
     }
diff --git a/src/pointer-analysis/value_set_fi.h b/src/pointer-analysis/value_set_fi.h
index 83affdb4ad4..fa8ddb551b6 100644
--- a/src/pointer-analysis/value_set_fi.h
+++ b/src/pointer-analysis/value_set_fi.h
@@ -10,7 +10,9 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_POINTER_ANALYSIS_VALUE_SET_FI_H
 #define CPROVER_POINTER_ANALYSIS_VALUE_SET_FI_H
 
+#include <map>
 #include <set>
+#include <unordered_set>
 
 #include <util/mp_arith.h>
 #include <util/namespace.h>
@@ -148,20 +150,20 @@ class value_set_fit
     }
   };
 
-  typedef hash_set_cont<exprt, irep_hash> expr_sett;
+  typedef std::unordered_set<exprt, irep_hash> expr_sett;
 
   #ifdef USE_DSTRING
   typedef std::map<idt, entryt> valuest;
   typedef std::set<idt> flatten_seent;
-  typedef hash_set_cont<idt, irep_id_hash> gvs_recursion_sett;
-  typedef hash_set_cont<idt, irep_id_hash> recfind_recursion_sett;
-  typedef hash_set_cont<idt, irep_id_hash> assign_recursion_sett;
+  typedef std::unordered_set<idt, irep_id_hash> gvs_recursion_sett;
+  typedef std::unordered_set<idt, irep_id_hash> recfind_recursion_sett;
+  typedef std::unordered_set<idt, irep_id_hash> assign_recursion_sett;
   #else
-  typedef hash_map_cont<idt, entryt, string_hash> valuest;
-  typedef hash_set_cont<idt, string_hash> flatten_seent;
-  typedef hash_set_cont<idt, string_hash> gvs_recursion_sett;
-  typedef hash_set_cont<idt, string_hash> recfind_recursion_sett;
-  typedef hash_set_cont<idt, string_hash> assign_recursion_sett;
+  typedef std::unordered_map<idt, entryt, string_hash> valuest;
+  typedef std::unordered_set<idt, string_hash> flatten_seent;
+  typedef std::unordered_set<idt, string_hash> gvs_recursion_sett;
+  typedef std::unordered_set<idt, string_hash> recfind_recursion_sett;
+  typedef std::unordered_set<idt, string_hash> assign_recursion_sett;
   #endif
 
   void get_value_set(
diff --git a/src/pointer-analysis/value_set_fivr.cpp b/src/pointer-analysis/value_set_fivr.cpp
index 872e5ba27f2..c6c5c8920d2 100644
--- a/src/pointer-analysis/value_set_fivr.cpp
+++ b/src/pointer-analysis/value_set_fivr.cpp
@@ -15,7 +15,6 @@ Author: Daniel Kroening, kroening@kroening.com,
 #include <util/expr_util.h>
 #include <util/base_type.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/prefix.h>
 #include <util/std_code.h>
 #include <util/arith_tools.h>
@@ -123,7 +122,7 @@ void value_set_fivrt::output(
     {
       const exprt &o=object_numbering[o_it->first];
 
-      std::string result="<"; //+i2string(o_it->first) + ",";
+      std::string result="<"; //+std::to_string(o_it->first) + ",";
 
       if(o.id()==ID_invalid)
       {
@@ -1720,7 +1719,7 @@ void value_set_fivrt::do_function_call(
   for(unsigned i=0; i<arguments.size(); i++)
   {
     const std::string identifier="value_set::" + id2string(function) + "::" +
-                                 "argument$"+i2string(i);
+                                 "argument$"+std::to_string(i);
     add_var(identifier, "");
     exprt dummy_lhs=symbol_exprt(identifier, arguments[i].type());
 //    std::cout << arguments[i] << std::endl;
@@ -1753,7 +1752,7 @@ void value_set_fivrt::do_function_call(
 
     const exprt v_expr=
       symbol_exprt("value_set::" + id2string(function) + "::" +
-                   "argument$"+i2string(i), it->type());
+                   "argument$"+std::to_string(i), it->type());
 
     exprt actual_lhs=symbol_exprt(identifier, it->type());
     assign(actual_lhs, v_expr, ns, true);
@@ -1779,7 +1778,7 @@ void value_set_fivrt::do_end_function(
 {
   if(lhs.is_nil()) return;
 
-  std::string rvs = "value_set::return_value" + i2string(from_function);
+  std::string rvs = "value_set::return_value" + std::to_string(from_function);
   symbol_exprt rhs(rvs, lhs.type());
 
   assign(lhs, rhs, ns);
@@ -1877,7 +1876,7 @@ void value_set_fivrt::apply_code(
     // this is turned into an assignment
     if(code.operands().size()==1)
     {
-      std::string rvs = "value_set::return_value" + i2string(from_function);
+      std::string rvs = "value_set::return_value" + std::to_string(from_function);
       symbol_exprt lhs(rvs, code.op0().type());
       assign(lhs, code.op0(), ns);
     }
diff --git a/src/pointer-analysis/value_set_fivr.h b/src/pointer-analysis/value_set_fivr.h
index d93aab134bc..e0bb75c0428 100644
--- a/src/pointer-analysis/value_set_fivr.h
+++ b/src/pointer-analysis/value_set_fivr.h
@@ -10,6 +10,10 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_POINTER_ANALYSIS_VALUE_SET_FIVR_H
 #define CPROVER_POINTER_ANALYSIS_VALUE_SET_FIVR_H
 
+#include <list>
+#include <map>
+#include <unordered_set>
+
 #include <util/mp_arith.h>
 #include <util/namespace.h>
 #include <util/reference_counting.h>
@@ -187,20 +191,20 @@ class value_set_fivrt
     }
   };
 
-  typedef hash_set_cont<exprt, irep_hash> expr_sett;
+  typedef std::unordered_set<exprt, irep_hash> expr_sett;
 
   #ifdef USE_DSTRING
   typedef std::map<idt, entryt> valuest;
-  typedef hash_set_cont<idt, irep_id_hash> flatten_seent;
-  typedef hash_set_cont<idt, irep_id_hash> gvs_recursion_sett;
-  typedef hash_set_cont<idt, irep_id_hash> recfind_recursion_sett;
-  typedef hash_set_cont<idt, irep_id_hash> assign_recursion_sett;
+  typedef std::unordered_set<idt, irep_id_hash> flatten_seent;
+  typedef std::unordered_set<idt, irep_id_hash> gvs_recursion_sett;
+  typedef std::unordered_set<idt, irep_id_hash> recfind_recursion_sett;
+  typedef std::unordered_set<idt, irep_id_hash> assign_recursion_sett;
   #else
-  typedef hash_map_cont<idt, entryt, string_hash> valuest;
-  typedef hash_set_cont<idt, string_hash> flatten_seent;
-  typedef hash_set_cont<idt, string_hash> gvs_recursion_sett;
-  typedef hash_set_cont<idt, string_hash> recfind_recursion_sett;
-  typedef hash_set_cont<idt, string_hash> assign_recursion_sett;
+  typedef std::unordered_map<idt, entryt, string_hash> valuest;
+  typedef std::unordered_set<idt, string_hash> flatten_seent;
+  typedef std::unordered_set<idt, string_hash> gvs_recursion_sett;
+  typedef std::unordered_set<idt, string_hash> recfind_recursion_sett;
+  typedef std::unordered_set<idt, string_hash> assign_recursion_sett;
   #endif
 
   void get_value_set(
diff --git a/src/pointer-analysis/value_set_fivrns.cpp b/src/pointer-analysis/value_set_fivrns.cpp
index 239ff5e0d73..10e7c94006a 100644
--- a/src/pointer-analysis/value_set_fivrns.cpp
+++ b/src/pointer-analysis/value_set_fivrns.cpp
@@ -15,7 +15,6 @@ Author: Daniel Kroening, kroening@kroening.com,
 #include <util/expr_util.h>
 #include <util/base_type.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/prefix.h>
 #include <util/std_code.h>
 #include <util/arith_tools.h>
@@ -126,7 +125,7 @@ void value_set_fivrnst::output_entry(
   {
     const exprt &o=object_numbering[o_it->first];
 
-    std::string result="<"; //+i2string(o_it->first) + ",";
+    std::string result="<"; //+std::to_string(o_it->first) + ",";
 
     if(o.id()==ID_invalid)
     {
@@ -1351,7 +1350,7 @@ void value_set_fivrnst::do_function_call(
   for(unsigned i=0; i<arguments.size(); i++)
   {
     const std::string identifier="value_set::" + id2string(function) + "::" +
-                                 "argument$"+i2string(i);
+                                 "argument$"+std::to_string(i);
     add_var(identifier, "");
     exprt dummy_lhs=symbol_exprt(identifier, arguments[i].type());
 //    std::cout << arguments[i] << std::endl;
@@ -1384,7 +1383,7 @@ void value_set_fivrnst::do_function_call(
 
     const exprt v_expr=
       symbol_exprt("value_set::" + id2string(function) + "::" +
-                   "argument$"+i2string(i), it->type());
+                   "argument$"+std::to_string(i), it->type());
 
     exprt actual_lhs=symbol_exprt(identifier, it->type());
     assign(actual_lhs, v_expr, ns, true);
@@ -1411,7 +1410,7 @@ void value_set_fivrnst::do_end_function(
   if(lhs.is_nil()) return;
 
   irep_idt rvs = std::string("value_set::return_value") +
-                 i2string(from_function);
+                 std::to_string(from_function);
   add_var(rvs, "");
   symbol_exprt rhs(rvs, lhs.type());
 
@@ -1511,7 +1510,7 @@ void value_set_fivrnst::apply_code(
     if(code.operands().size()==1)
     {
       irep_idt rvs = std::string("value_set::return_value") +
-                     i2string(from_function);
+                     std::to_string(from_function);
       add_var(rvs, "");
       symbol_exprt lhs(rvs, code.op0().type());
       assign(lhs, code.op0(), ns);
diff --git a/src/pointer-analysis/value_set_fivrns.h b/src/pointer-analysis/value_set_fivrns.h
index b6b02f3c93b..8031f760e18 100644
--- a/src/pointer-analysis/value_set_fivrns.h
+++ b/src/pointer-analysis/value_set_fivrns.h
@@ -10,6 +10,11 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_POINTER_ANALYSIS_VALUE_SET_FIVRNS_H
 #define CPROVER_POINTER_ANALYSIS_VALUE_SET_FIVRNS_H
 
+#include <list>
+#include <map>
+#include <string>
+#include <unordered_set>
+
 #include <util/mp_arith.h>
 #include <util/namespace.h>
 #include <util/reference_counting.h>
@@ -186,12 +191,12 @@ class value_set_fivrnst
     }
   };
 
-  typedef hash_set_cont<exprt, irep_hash> expr_sett;
+  typedef std::unordered_set<exprt, irep_hash> expr_sett;
 
   #ifdef USE_DSTRING
   typedef std::map<idt, entryt> valuest;
   #else
-  typedef hash_map_cont<idt, entryt, string_hash> valuest;
+  typedef std::unordered_map<idt, entryt, string_hash> valuest;
   #endif
 
   void get_value_set(
diff --git a/src/solvers/cvc/cvc_conv.cpp b/src/solvers/cvc/cvc_conv.cpp
index c1c7badc682..2a39409d5e3 100644
--- a/src/solvers/cvc/cvc_conv.cpp
+++ b/src/solvers/cvc/cvc_conv.cpp
@@ -13,7 +13,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/std_types.h>
 #include <util/std_expr.h>
 #include <util/config.h>
-#include <util/i2string.h>
 #include <util/expr_util.h>
 #include <util/find_symbols.h>
 #include <util/pointer_offset_size.h>
@@ -129,7 +128,7 @@ std::string cvc_convt::cvc_pointer_type()
 {
   assert(config.ansi_c.pointer_width!=0);
   return "[# object: INT, offset: BITVECTOR("+
-         i2string(config.ansi_c.pointer_width)+") #]";
+         std::to_string(config.ansi_c.pointer_width)+") #]";
 }
 
 /*******************************************************************\
@@ -147,7 +146,7 @@ Function: cvc_convt::array_index_type
 std::string cvc_convt::array_index_type()
 {
   return std::string("BITVECTOR(")+
-         i2string(32)+")";
+         std::to_string(32)+")";
 }
 
 /*******************************************************************\
@@ -1304,7 +1303,7 @@ void cvc_convt::set_to(const exprt &expr, bool value)
 
       if(id.type.is_nil())
       {
-        hash_set_cont<irep_idt, irep_id_hash> s_set;
+        std::unordered_set<irep_idt, irep_id_hash> s_set;
 
         ::find_symbols(expr.op1(), s_set);
 
diff --git a/src/solvers/cvc/cvc_conv.h b/src/solvers/cvc/cvc_conv.h
index 87f8a1c65ca..edf9720d0eb 100644
--- a/src/solvers/cvc/cvc_conv.h
+++ b/src/solvers/cvc/cvc_conv.h
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_SOLVERS_CVC_CVC_CONV_H
 #define CPROVER_SOLVERS_CVC_CVC_CONV_H
 
-#include <util/hash_cont.h>
 
 #include <solvers/prop/prop_conv.h>
 #include <solvers/flattening/pointer_logic.h>
@@ -56,7 +55,7 @@ class cvc_convt:public prop_convt
     }
   };
 
-  typedef hash_map_cont<irep_idt, identifiert, irep_id_hash>
+  typedef std::unordered_map<irep_idt, identifiert, irep_id_hash>
     identifier_mapt;
 
   identifier_mapt identifier_map;
diff --git a/src/solvers/cvc/cvc_dec.cpp b/src/solvers/cvc/cvc_dec.cpp
index 2a3832b62e2..3b174ac4c2f 100644
--- a/src/solvers/cvc/cvc_dec.cpp
+++ b/src/solvers/cvc/cvc_dec.cpp
@@ -24,7 +24,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #define getpid _getpid
 #endif
 
-#include <util/i2string.h>
 #include <util/prefix.h>
 #include <util/string2int.h>
 
@@ -44,7 +43,7 @@ Function: cvc_temp_filet::cvc_temp_filet
 
 cvc_temp_filet::cvc_temp_filet()
 {
-  temp_out_filename="cvc_dec_out_"+i2string(getpid())+".tmp";
+  temp_out_filename="cvc_dec_out_"+std::to_string(getpid())+".tmp";
 
   temp_out.open(
     temp_out_filename.c_str(),
@@ -94,7 +93,7 @@ decision_proceduret::resultt cvc_dect::dec_solve()
   temp_out.close();
 
   temp_result_filename=
-    "cvc_dec_result_"+i2string(getpid())+".tmp";
+    "cvc_dec_result_"+std::to_string(getpid())+".tmp";
 
   std::string command=
     "cvcl "+temp_out_filename+" > "+temp_result_filename+" 2>&1";
@@ -167,7 +166,7 @@ void cvc_dect::read_assert(std::istream &in, std::string &line)
 
     if(line[0]=='l')
     {
-      unsigned number=unsafe_c_str2unsigned(line.c_str()+1);
+      unsigned number=unsafe_string2unsigned(line.substr(1));
       assert(number<no_boolean_variables);
       assert(no_boolean_variables==boolean_assignment.size());
       boolean_assignment[number]=value;
diff --git a/src/solvers/cvc/cvc_prop.cpp b/src/solvers/cvc/cvc_prop.cpp
index c960ccf82f6..d941e6c8235 100644
--- a/src/solvers/cvc/cvc_prop.cpp
+++ b/src/solvers/cvc/cvc_prop.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <cassert>
 #include <set>
 
-#include <util/i2string.h>
 
 #include "cvc_prop.h"
 
@@ -565,9 +564,9 @@ std::string cvc_propt::cvc_literal(literalt l)
     return "TRUE";
 
   if(l.sign())
-    return "(NOT l"+i2string(l.var_no())+")";
+    return "(NOT l"+std::to_string(l.var_no())+")";
 
-  return "l"+i2string(l.var_no());
+  return "l"+std::to_string(l.var_no());
 }
 
 /*******************************************************************\
diff --git a/src/solvers/dplib/dplib_conv.cpp b/src/solvers/dplib/dplib_conv.cpp
index 7055c5c0015..58b7702f927 100644
--- a/src/solvers/dplib/dplib_conv.cpp
+++ b/src/solvers/dplib/dplib_conv.cpp
@@ -13,7 +13,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/std_types.h>
 #include <util/std_expr.h>
 #include <util/config.h>
-#include <util/i2string.h>
 #include <util/expr_util.h>
 #include <util/find_symbols.h>
 #include <util/pointer_offset_size.h>
@@ -59,7 +58,7 @@ std::string dplib_convt::dplib_pointer_type()
 {
   assert(config.ansi_c.pointer_width!=0);
   return "[# object: INT, offset: BITVECTOR("+
-         i2string(config.ansi_c.pointer_width)+") #]";
+         std::to_string(config.ansi_c.pointer_width)+") #]";
 }
 
 /*******************************************************************\
@@ -76,7 +75,7 @@ Function: dplib_convt::array_index_type
 
 std::string dplib_convt::array_index_type()
 {
-  return std::string("SIGNED [")+i2string(32)+"]";
+  return std::string("SIGNED [")+std::to_string(32)+"]";
 }
 
 /*******************************************************************\
@@ -1128,7 +1127,7 @@ void dplib_convt::set_to(const exprt &expr, bool value)
 
       if(id.type.is_nil())
       {
-        hash_set_cont<irep_idt, irep_id_hash> s_set;
+        std::unordered_set<irep_idt, irep_id_hash> s_set;
 
         ::find_symbols(expr.op1(), s_set);
 
diff --git a/src/solvers/dplib/dplib_conv.h b/src/solvers/dplib/dplib_conv.h
index 494bcb1fb12..a4f2f0558f4 100644
--- a/src/solvers/dplib/dplib_conv.h
+++ b/src/solvers/dplib/dplib_conv.h
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_SOLVERS_DPLIB_DPLIB_CONV_H
 #define CPROVER_SOLVERS_DPLIB_DPLIB_CONV_H
 
-#include <util/hash_cont.h>
 
 #include <solvers/prop/prop_conv.h>
 #include <solvers/flattening/pointer_logic.h>
@@ -64,7 +63,7 @@ class dplib_convt:public prop_convt
     }
   };
 
-  typedef hash_map_cont<irep_idt, identifiert, irep_id_hash>
+  typedef std::unordered_map<irep_idt, identifiert, irep_id_hash>
     identifier_mapt;
 
   identifier_mapt identifier_map;
diff --git a/src/solvers/dplib/dplib_dec.cpp b/src/solvers/dplib/dplib_dec.cpp
index 31403a1b2f3..c4775cb5007 100644
--- a/src/solvers/dplib/dplib_dec.cpp
+++ b/src/solvers/dplib/dplib_dec.cpp
@@ -23,7 +23,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #define getpid _getpid
 #endif
 
-#include <util/i2string.h>
 #include <util/prefix.h>
 #include <util/string2int.h>
 
@@ -43,7 +42,7 @@ Function: dplib_temp_filet::dplib_temp_filet
 
 dplib_temp_filet::dplib_temp_filet()
 {
-  temp_out_filename="dplib_dec_out_"+i2string(getpid())+".tmp";
+  temp_out_filename="dplib_dec_out_"+std::to_string(getpid())+".tmp";
 
   temp_out.open(
     temp_out_filename.c_str(),
@@ -95,7 +94,7 @@ decision_proceduret::resultt dplib_dect::dec_solve()
   temp_out.close();
 
   temp_result_filename=
-    "dplib_dec_result_"+i2string(getpid())+".tmp";
+    "dplib_dec_result_"+std::to_string(getpid())+".tmp";
 
   std::string command=
     "dplibl "+temp_out_filename+" > "+temp_result_filename+" 2>&1";
diff --git a/src/solvers/dplib/dplib_prop.cpp b/src/solvers/dplib/dplib_prop.cpp
index 7f94b1184b3..ea9e169ffda 100644
--- a/src/solvers/dplib/dplib_prop.cpp
+++ b/src/solvers/dplib/dplib_prop.cpp
@@ -10,7 +10,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <set>
 
-#include <util/i2string.h>
 
 #include "dplib_prop.h"
 
@@ -542,9 +541,9 @@ std::string dplib_propt::dplib_literal(literalt l)
     return "TRUE";
 
   if(l.sign())
-    return "(NOT l"+i2string(l.var_no())+")";
+    return "(NOT l"+std::to_string(l.var_no())+")";
 
-  return "l"+i2string(l.var_no());
+  return "l"+std::to_string(l.var_no());
 }
 
 /*******************************************************************\
diff --git a/src/solvers/flattening/boolbv.cpp b/src/solvers/flattening/boolbv.cpp
index 16a3cd467e8..ca602dcd6b6 100644
--- a/src/solvers/flattening/boolbv.cpp
+++ b/src/solvers/flattening/boolbv.cpp
@@ -13,7 +13,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <util/symbol.h>
 #include <util/mp_arith.h>
-#include <util/i2string.h>
 #include <util/arith_tools.h>
 #include <util/replace_expr.h>
 #include <util/std_types.h>
@@ -800,7 +799,7 @@ void boolbvt::make_bv_expr(const typet &type, const bvt &bv, exprt &dest)
   bv_sub.resize(bv.size());
 
   for(std::size_t i=0; i<bv.size(); i++)
-    bv_sub[i].id(i2string(bv[i].get()));
+    bv_sub[i].id(std::to_string(bv[i].get()));
 }
 
 /*******************************************************************\
diff --git a/src/solvers/flattening/boolbv.h b/src/solvers/flattening/boolbv.h
index 4d2a6fd6367..9289591a79d 100644
--- a/src/solvers/flattening/boolbv.h
+++ b/src/solvers/flattening/boolbv.h
@@ -13,7 +13,6 @@ Author: Daniel Kroening, kroening@kroening.com
 // convert expression to boolean formula
 //
 
-#include <util/hash_cont.h>
 #include <util/mp_arith.h>
 #include <util/expr.h>
 #include <util/byte_operators.h>
@@ -111,7 +110,7 @@ class boolbvt:public arrayst
 
   bvt conversion_failed(const exprt &expr);
 
-  typedef hash_map_cont<const exprt, bvt, irep_hash> bv_cachet;
+  typedef std::unordered_map<const exprt, bvt, irep_hash> bv_cachet;
   bv_cachet bv_cache;
 
   bool type_conversion(
diff --git a/src/solvers/flattening/boolbv_equality.cpp b/src/solvers/flattening/boolbv_equality.cpp
index ab9a1c99d51..8fedbbaed8d 100644
--- a/src/solvers/flattening/boolbv_equality.cpp
+++ b/src/solvers/flattening/boolbv_equality.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <iostream>
 
-#include <util/i2string.h>
 #include <util/std_expr.h>
 #include <util/base_type.h>
 
diff --git a/src/solvers/flattening/boolbv_extractbits.cpp b/src/solvers/flattening/boolbv_extractbits.cpp
index 1a6177138e9..7ec5a6987c4 100644
--- a/src/solvers/flattening/boolbv_extractbits.cpp
+++ b/src/solvers/flattening/boolbv_extractbits.cpp
@@ -7,7 +7,6 @@ Author: Daniel Kroening, kroening@kroening.com
 \*******************************************************************/
 
 #include <util/arith_tools.h>
-#include <util/i2string.h>
 
 #include "boolbv.h"
 
diff --git a/src/solvers/flattening/boolbv_index.cpp b/src/solvers/flattening/boolbv_index.cpp
index 35cbb8f54e1..e01b18ea5c0 100644
--- a/src/solvers/flattening/boolbv_index.cpp
+++ b/src/solvers/flattening/boolbv_index.cpp
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/arith_tools.h>
 #include <util/std_expr.h>
 #include <util/simplify_expr.h>
-#include <util/i2string.h>
 
 #include "boolbv.h"
 
@@ -124,7 +123,7 @@ bvt boolbvt::convert_index(const index_exprt &expr)
 
       std::string identifier=
         "__CPROVER_internal_uniform_array_"+
-        i2string(uniform_array_counter++);
+        std::to_string(uniform_array_counter++);
 
       symbol_exprt result(identifier, expr.type());
       bv = convert_bv(result);
@@ -165,7 +164,7 @@ bvt boolbvt::convert_index(const index_exprt &expr)
 
       std::string identifier=
         "__CPROVER_internal_actual_array_"+
-        i2string(actual_array_counter++);
+        std::to_string(actual_array_counter++);
 
       symbol_exprt result(identifier, expr.type());
       bv = convert_bv(result);
diff --git a/src/solvers/flattening/boolbv_map.h b/src/solvers/flattening/boolbv_map.h
index 0d4bc2e1c4d..1f2b7458f93 100644
--- a/src/solvers/flattening/boolbv_map.h
+++ b/src/solvers/flattening/boolbv_map.h
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <vector>
 
-#include <util/hash_cont.h>
 #include <util/type.h>
 #include <util/namespace.h>
 
@@ -55,7 +54,7 @@ class boolbv_mapt
     std::string get_value(const propt &) const;
   };
 
-  typedef hash_map_cont<irep_idt, map_entryt, irep_id_hash> mappingt;
+  typedef std::unordered_map<irep_idt, map_entryt, irep_id_hash> mappingt;
   mappingt mapping;
 
   void show() const;
diff --git a/src/solvers/flattening/boolbv_overflow.cpp b/src/solvers/flattening/boolbv_overflow.cpp
index 4d6b6fdb670..87c513ae5db 100644
--- a/src/solvers/flattening/boolbv_overflow.cpp
+++ b/src/solvers/flattening/boolbv_overflow.cpp
@@ -119,7 +119,7 @@ literalt boolbvt::convert_overflow(const exprt &expr)
   }
   else if(has_prefix(expr.id_string(), "overflow-typecast-"))
   {
-    std::size_t bits=unsafe_c_str2unsigned(expr.id().c_str()+18);
+    std::size_t bits=unsafe_string2unsigned(id2string(expr.id()).substr(18));
 
     const exprt::operandst &operands=expr.operands();
 
diff --git a/src/solvers/flattening/boolbv_width.h b/src/solvers/flattening/boolbv_width.h
index 80e27d03e5c..6014dd7b198 100644
--- a/src/solvers/flattening/boolbv_width.h
+++ b/src/solvers/flattening/boolbv_width.h
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <util/std_types.h>
 #include <util/namespace.h>
-#include <util/hash_cont.h>
 
 class boolbv_widtht
 {
@@ -42,7 +41,7 @@ class boolbv_widtht
     std::vector<membert> members;
   };
 
-  typedef hash_map_cont<typet, entryt, irep_hash> cachet;
+  typedef std::unordered_map<typet, entryt, irep_hash> cachet;
 
   // the 'mutable' is allow const methods above
   mutable cachet cache;
diff --git a/src/solvers/flattening/bv_pointers.cpp b/src/solvers/flattening/bv_pointers.cpp
index c6dee2eb4cd..b4d0382f27a 100644
--- a/src/solvers/flattening/bv_pointers.cpp
+++ b/src/solvers/flattening/bv_pointers.cpp
@@ -6,9 +6,7 @@ Author: Daniel Kroening, kroening@kroening.com
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/config.h>
-#include <util/c_misc.h>
 #include <util/arith_tools.h>
 #include <util/prefix.h>
 #include <util/std_expr.h>
diff --git a/src/solvers/flattening/bv_pointers.h b/src/solvers/flattening/bv_pointers.h
index eafed0e6dfb..66253731cbc 100644
--- a/src/solvers/flattening/bv_pointers.h
+++ b/src/solvers/flattening/bv_pointers.h
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_SOLVERS_FLATTENING_BV_POINTERS_H
 #define CPROVER_SOLVERS_FLATTENING_BV_POINTERS_H
 
-#include <util/hash_cont.h>
 
 #include "boolbv.h"
 #include "pointer_logic.h"
diff --git a/src/solvers/flattening/equality.h b/src/solvers/flattening/equality.h
index 533f406e010..741552c76f3 100644
--- a/src/solvers/flattening/equality.h
+++ b/src/solvers/flattening/equality.h
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <map>
 
-#include <util/hash_cont.h>
 #include <util/expr.h>
 
 #include <solvers/prop/prop_conv.h>
@@ -33,7 +32,7 @@ class equalityt:public prop_conv_solvert
   }
 
 protected:
-  typedef hash_map_cont<const exprt, unsigned, irep_hash> elementst;
+  typedef std::unordered_map<const exprt, unsigned, irep_hash> elementst;
   typedef std::map<std::pair<unsigned, unsigned>, literalt> equalitiest;
   typedef std::map<unsigned, exprt> elements_revt;
 
@@ -44,7 +43,7 @@ class equalityt:public prop_conv_solvert
     equalitiest equalities;
   };
 
-  typedef hash_map_cont<const typet, typestructt, irep_hash> typemapt;
+  typedef std::unordered_map<const typet, typestructt, irep_hash> typemapt;
 
   typemapt typemap;
 
diff --git a/src/solvers/flattening/pointer_logic.cpp b/src/solvers/flattening/pointer_logic.cpp
index 4cb77d56b01..ff6568c969c 100644
--- a/src/solvers/flattening/pointer_logic.cpp
+++ b/src/solvers/flattening/pointer_logic.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
-#include <util/i2string.h>
 #include <util/arith_tools.h>
 #include <util/std_expr.h>
 #include <util/prefix.h>
@@ -157,7 +156,7 @@ exprt pointer_logict::pointer_expr(
   if(pointer.object>=objects.size())
   {
     constant_exprt result(type);
-    result.set_value("INVALID-"+i2string(pointer.object));
+    result.set_value("INVALID-"+std::to_string(pointer.object));
     return result;
   }
 
diff --git a/src/solvers/flattening/pointer_logic.h b/src/solvers/flattening/pointer_logic.h
index 88232ef5e32..bcf18ca69f7 100644
--- a/src/solvers/flattening/pointer_logic.h
+++ b/src/solvers/flattening/pointer_logic.h
@@ -10,7 +10,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #define CPROVER_SOLVERS_FLATTENING_POINTER_LOGIC_H
 
 #include <util/mp_arith.h>
-#include <util/hash_cont.h>
 #include <util/expr.h>
 #include <util/numbering.h>
 
diff --git a/src/solvers/floatbv/float_bv.h b/src/solvers/floatbv/float_bv.h
index 10c2b4089e8..d71ef8be4e9 100644
--- a/src/solvers/floatbv/float_bv.h
+++ b/src/solvers/floatbv/float_bv.h
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_SOLVERS_FLOATBV_FLOAT_BV_H
 #define CPROVER_SOLVERS_FLOATBV_FLOAT_BV_H
 
-#include <util/i2string.h>
 #include <util/ieee_float.h>
 #include <util/std_expr.h>
 
diff --git a/src/solvers/prop/aig.cpp b/src/solvers/prop/aig.cpp
index 42c7713b364..5d5c9839f8e 100644
--- a/src/solvers/prop/aig.cpp
+++ b/src/solvers/prop/aig.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <cassert>
 #include <ostream>
 
-#include <util/i2string.h>
 
 #include "aig.h"
 
@@ -27,7 +26,7 @@ Function: aigt::label
 
 std::string aigt::label(nodest::size_type v) const
 {
-  return "var("+i2string(v)+")";
+  return "var("+std::to_string(v)+")";
 }
 
 /*******************************************************************\
@@ -44,7 +43,7 @@ Function: aigt::dot_label
 
 std::string aigt::dot_label(nodest::size_type v) const
 {
-  return "var("+i2string(v)+")";
+  return "var("+std::to_string(v)+")";
 }
 
 /*******************************************************************\
diff --git a/src/solvers/prop/bdd_expr.h b/src/solvers/prop/bdd_expr.h
index d34372b300b..608be1694e2 100644
--- a/src/solvers/prop/bdd_expr.h
+++ b/src/solvers/prop/bdd_expr.h
@@ -39,7 +39,7 @@ class bdd_exprt
   miniBDD::mgr bdd_mgr;
   BDDt root;
 
-  typedef hash_map_cont<exprt, BDDt, irep_hash> expr_mapt;
+  typedef std::unordered_map<exprt, BDDt, irep_hash> expr_mapt;
   expr_mapt expr_map;
   typedef std::map<unsigned, exprt> node_mapt;
   node_mapt node_map;
diff --git a/src/solvers/prop/prop_conv.h b/src/solvers/prop/prop_conv.h
index 76b496be13a..f250ea9e00a 100644
--- a/src/solvers/prop/prop_conv.h
+++ b/src/solvers/prop/prop_conv.h
@@ -12,7 +12,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <string>
 #include <map>
 
-#include <util/hash_cont.h>
 #include <util/decision_procedure.h>
 #include <util/expr.h>
 #include <util/std_expr.h>
@@ -106,7 +105,7 @@ class prop_conv_solvert:public prop_convt
   virtual void clear_cache() { cache.clear();}
 
   typedef std::map<irep_idt, literalt> symbolst;
-  typedef hash_map_cont<exprt, literalt, irep_hash> cachet;
+  typedef std::unordered_map<exprt, literalt, irep_hash> cachet;
 
   const cachet &get_cache() const { return cache; }
   const symbolst &get_symbols() const { return symbols; }
diff --git a/src/solvers/qbf/qbf_bdd_core.cpp b/src/solvers/qbf/qbf_bdd_core.cpp
index b4df80a92ca..4d4f17da6be 100644
--- a/src/solvers/qbf/qbf_bdd_core.cpp
+++ b/src/solvers/qbf/qbf_bdd_core.cpp
@@ -9,7 +9,6 @@ Author: CM Wintersteiger
 #include <cassert>
 #include <fstream>
 
-#include <util/i2string.h>
 #include <util/arith_tools.h>
 #include <util/std_expr.h>
 
@@ -192,8 +191,8 @@ propt::resultt qbf_bdd_coret::prop_solve()
   {
     std::string msg=
       solver_text() + ": "+
-      i2string(no_variables())+" variables, "+
-      i2string(matrix->nodeCount())+" nodes";
+      std::to_string(no_variables())+" variables, "+
+      std::to_string(matrix->nodeCount())+" nodes";
     messaget::status() << msg << messaget::eom;
   }
 
diff --git a/src/solvers/qbf/qbf_bdd_core.h b/src/solvers/qbf/qbf_bdd_core.h
index 801cf4417e9..4fc8fd1abaa 100644
--- a/src/solvers/qbf/qbf_bdd_core.h
+++ b/src/solvers/qbf/qbf_bdd_core.h
@@ -11,7 +11,6 @@ Author: CM Wintersteiger
 
 #include <vector>
 
-#include <util/hash_cont.h>
 
 #include "qdimacs_core.h"
 
@@ -26,7 +25,7 @@ class qbf_bdd_certificatet : public qdimacs_coret
   typedef std::vector<BDD*> model_bddst;
   model_bddst model_bdds;
 
-  typedef hash_map_cont<unsigned, exprt> function_cachet;
+  typedef std::unordered_map<unsigned, exprt> function_cachet;
   function_cachet function_cache;
 
 public:
diff --git a/src/solvers/qbf/qbf_skizzo_core.cpp b/src/solvers/qbf/qbf_skizzo_core.cpp
index 91ebc01913b..127f4a9e42e 100644
--- a/src/solvers/qbf/qbf_skizzo_core.cpp
+++ b/src/solvers/qbf/qbf_skizzo_core.cpp
@@ -9,7 +9,6 @@ Author: CM Wintersteiger
 #include <cassert>
 #include <fstream>
 
-#include <util/i2string.h>
 #include <util/string2int.h>
 
 #include <cuddObj.hh> // CUDD Library
@@ -102,8 +101,8 @@ propt::resultt qbf_skizzo_coret::prop_solve()
   {
     std::string msg=
       "Skizzo: "+
-      i2string(no_variables())+" variables, "+
-      i2string(no_clauses())+" clauses";
+      std::to_string(no_variables())+" variables, "+
+      std::to_string(no_clauses())+" clauses";
     messaget::status() << msg << messaget::eom;
   }
 
diff --git a/src/solvers/qbf/qbf_squolem.cpp b/src/solvers/qbf/qbf_squolem.cpp
index 3033babc937..f6fa86278ab 100644
--- a/src/solvers/qbf/qbf_squolem.cpp
+++ b/src/solvers/qbf/qbf_squolem.cpp
@@ -6,7 +6,6 @@ Author: CM Wintersteiger
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 
 #include "qbf_squolem.h"
 
@@ -94,8 +93,8 @@ propt::resultt qbf_squolemt::prop_solve()
   {
     std::string msg=
       "Squolem: "+
-      i2string(no_variables())+" variables, "+
-      i2string(no_clauses())+" clauses";
+      std::to_string(no_variables())+" variables, "+
+      std::to_string(no_clauses())+" clauses";
     messaget::status() << msg << messaget::eom;
   }
 
diff --git a/src/solvers/qbf/qbf_squolem_core.cpp b/src/solvers/qbf/qbf_squolem_core.cpp
index dba0b05f45e..e076e9341a2 100644
--- a/src/solvers/qbf/qbf_squolem_core.cpp
+++ b/src/solvers/qbf/qbf_squolem_core.cpp
@@ -8,7 +8,6 @@ Author: CM Wintersteiger
 
 #include <algorithm>
 
-#include <util/i2string.h>
 #include <util/std_expr.h>
 #include <util/arith_tools.h>
 
@@ -166,8 +165,8 @@ propt::resultt qbf_squolem_coret::prop_solve()
   {
     std::string msg=
       "Squolem: "+
-      i2string(no_variables())+" variables, "+
-      i2string(no_clauses())+" clauses";
+      std::to_string(no_variables())+" variables, "+
+      std::to_string(no_clauses())+" clauses";
     messaget::status() << msg << messaget::eom;
   }
 
diff --git a/src/solvers/qbf/qbf_squolem_core.h b/src/solvers/qbf/qbf_squolem_core.h
index 7227e5dee27..c09f7d69713 100644
--- a/src/solvers/qbf/qbf_squolem_core.h
+++ b/src/solvers/qbf/qbf_squolem_core.h
@@ -9,7 +9,6 @@ Author: CM Wintersteiger
 #ifndef CPROVER_SOLVERS_QBF_QBF_SQUOLEM_CORE_H
 #define CPROVER_SOLVERS_QBF_QBF_SQUOLEM_CORE_H
 
-#include <util/hash_cont.h>
 #include <quannon/squolem2/squolem2.h>
 
 #include "qdimacs_core.h"
@@ -47,7 +46,7 @@ class qbf_squolem_coret:public qdimacs_coret
   virtual const exprt f_get(literalt l);
 
 private:
-  typedef hash_map_cont<unsigned, exprt> function_cachet;
+  typedef std::unordered_map<unsigned, exprt> function_cachet;
     function_cachet function_cache;
 
   const exprt f_get_cnf(WitnessStack *wsp);
diff --git a/src/solvers/refinement/bv_refinement_loop.cpp b/src/solvers/refinement/bv_refinement_loop.cpp
index c319601e716..b6eb359bca7 100644
--- a/src/solvers/refinement/bv_refinement_loop.cpp
+++ b/src/solvers/refinement/bv_refinement_loop.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <iostream>
 
-#include <util/i2string.h>
 #include <util/xml.h>
 
 #include "bv_refinement.h"
@@ -87,7 +86,7 @@ decision_proceduret::resultt bv_refinementt::dec_solve()
     if(ui==ui_message_handlert::XML_UI)
     {
       xmlt xml("refinement-iteration");
-      xml.data=i2string(iteration);
+      xml.data=std::to_string(iteration);
       std::cout << xml << '\n';
     }
 
diff --git a/src/solvers/refinement/refine_arithmetic.cpp b/src/solvers/refinement/refine_arithmetic.cpp
index 3e10a9e6c6a..eb774866c02 100644
--- a/src/solvers/refinement/refine_arithmetic.cpp
+++ b/src/solvers/refinement/refine_arithmetic.cpp
@@ -6,7 +6,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 \*******************************************************************/
 
-#include <util/i2string.h>
 #include <util/bv_arithmetic.h>
 #include <util/ieee_float.h>
 #include <util/expr_util.h>
@@ -673,6 +672,6 @@ std::string bv_refinementt::approximationt::as_string() const
   #if 0
   return from_expr(expr);
   #else
-  return i2string(id_nr)+"/"+id2string(expr.id());
+  return std::to_string(id_nr)+"/"+id2string(expr.id());
   #endif
 }
diff --git a/src/solvers/sat/satcheck_booleforce.cpp b/src/solvers/sat/satcheck_booleforce.cpp
index 5ea0ad75616..6fe9bb6784f 100644
--- a/src/solvers/sat/satcheck_booleforce.cpp
+++ b/src/solvers/sat/satcheck_booleforce.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
-#include <util/i2string.h>
 
 #include "satcheck_booleforce.h"
 
diff --git a/src/solvers/sat/satcheck_limmat.cpp b/src/solvers/sat/satcheck_limmat.cpp
index 7f9deb899e0..f99db080c7a 100644
--- a/src/solvers/sat/satcheck_limmat.cpp
+++ b/src/solvers/sat/satcheck_limmat.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
-#include <util/i2string.h>
 
 #include "satcheck_limmat.h"
 
@@ -156,8 +155,8 @@ propt::resultt satcheck_limmatt::prop_solve()
 
   {
     std::string msg=
-      i2string(maxvar_Limmat(solver))+" variables, "+
-      i2string(clauses_Limmat(solver))+" clauses";
+      std::to_string(maxvar_Limmat(solver))+" variables, "+
+      std::to_string(clauses_Limmat(solver))+" clauses";
     messaget::status() << msg << messaget::eom;
   }
 
diff --git a/src/solvers/sat/satcheck_lingeling.cpp b/src/solvers/sat/satcheck_lingeling.cpp
index 4d7e8c55148..4b058569ecf 100644
--- a/src/solvers/sat/satcheck_lingeling.cpp
+++ b/src/solvers/sat/satcheck_lingeling.cpp
@@ -8,7 +8,6 @@ Author: Michael Tautschnig, michael.tautschnig@cs.ox.ac.uk
 
 #include <cassert>
 
-#include <util/i2string.h>
 #include <util/threeval.h>
 
 #include "satcheck_lingeling.h"
@@ -117,8 +116,8 @@ propt::resultt satcheck_lingelingt::prop_solve()
   // We start counting at 1, thus there is one variable fewer.
   {
     std::string msg=
-      i2string(no_variables()-1)+" variables, "+
-      i2string(clause_counter)+" clauses";
+      std::to_string(no_variables()-1)+" variables, "+
+      std::to_string(clause_counter)+" clauses";
     messaget::status() << msg << messaget::eom;
   }
 
diff --git a/src/solvers/sat/satcheck_picosat.cpp b/src/solvers/sat/satcheck_picosat.cpp
index 63b8168298a..c701ab88823 100644
--- a/src/solvers/sat/satcheck_picosat.cpp
+++ b/src/solvers/sat/satcheck_picosat.cpp
@@ -8,7 +8,6 @@ Author: Michael Tautschnig, michael.tautschnig@cs.ox.ac.uk
 
 #include <cassert>
 
-#include <util/i2string.h>
 #include <util/threeval.h>
 
 #include "satcheck_picosat.h"
@@ -118,8 +117,8 @@ propt::resultt satcheck_picosatt::prop_solve()
 
   {
     std::string msg=
-      i2string(_no_variables-1)+" variables, "+
-      i2string(picosat_added_original_clauses(picosat))+" clauses";
+      std::to_string(_no_variables-1)+" variables, "+
+      std::to_string(picosat_added_original_clauses(picosat))+" clauses";
     messaget::status() << msg << messaget::eom;
   }
 
diff --git a/src/solvers/sat/satcheck_precosat.cpp b/src/solvers/sat/satcheck_precosat.cpp
index a04bf21618f..7589d085678 100644
--- a/src/solvers/sat/satcheck_precosat.cpp
+++ b/src/solvers/sat/satcheck_precosat.cpp
@@ -8,7 +8,6 @@ Author: Michael Tautschnig, michael.tautschnig@cs.ox.ac.uk
 
 #include <cassert>
 
-#include <util/i2string.h>
 #include <util/threeval.h>
 
 #include "satcheck_precosat.h"
@@ -117,8 +116,8 @@ propt::resultt satcheck_precosatt::prop_solve()
   // We start counting at 1, thus there is one variable fewer.
   {
     std::string msg=
-      i2string(no_variables()-1)+" variables, "+
-      i2string(solver->getAddedOrigClauses())+" clauses";
+      std::to_string(no_variables()-1)+" variables, "+
+      std::to_string(solver->getAddedOrigClauses())+" clauses";
     messaget::status() << msg << messaget::eom;
   }
 
diff --git a/src/solvers/sat/satcheck_smvsat.cpp b/src/solvers/sat/satcheck_smvsat.cpp
index 7feecb3bf0a..2316f07fd95 100644
--- a/src/solvers/sat/satcheck_smvsat.cpp
+++ b/src/solvers/sat/satcheck_smvsat.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <cassert>
 #include <stack>
 
-#include <util/i2string.h>
 
 #include "satcheck_smvsat.h"
 
diff --git a/src/solvers/sat/satcheck_zchaff.cpp b/src/solvers/sat/satcheck_zchaff.cpp
index 6af26cda57a..bcca0ff2f2b 100644
--- a/src/solvers/sat/satcheck_zchaff.cpp
+++ b/src/solvers/sat/satcheck_zchaff.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
-#include <util/i2string.h>
 
 #include "satcheck_zchaff.h"
 
@@ -151,8 +150,8 @@ propt::resultt satcheck_zchaff_baset::prop_solve()
 
   {
     std::string msg=
-      i2string(solver->num_variables())+" variables, "+
-      i2string(solver->clauses().size())+" clauses";
+      std::to_string(solver->num_variables())+" variables, "+
+      std::to_string(solver->clauses().size())+" clauses";
     messaget::status() << msg << messaget::eom;
   }
 
diff --git a/src/solvers/sat/satcheck_zcore.cpp b/src/solvers/sat/satcheck_zcore.cpp
index 5749b482508..700d632bfec 100644
--- a/src/solvers/sat/satcheck_zcore.cpp
+++ b/src/solvers/sat/satcheck_zcore.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <cassert>
 #include <fstream>
 
-#include <util/i2string.h>
 #include <util/string2int.h>
 
 #include "satcheck_zcore.h"
@@ -100,8 +99,8 @@ propt::resultt satcheck_zcoret::prop_solve()
   // We start counting at 1, thus there is one variable fewer.
   {
     std::string msg=
-      i2string(no_variables()-1)+" variables, "+
-      i2string(no_clauses())+" clauses";
+      std::to_string(no_variables()-1)+" variables, "+
+      std::to_string(no_clauses())+" clauses";
     messaget::status() << msg << messaget::eom;
   }
 
diff --git a/src/solvers/smt1/smt1_conv.cpp b/src/solvers/smt1/smt1_conv.cpp
index b89dc8b4525..44bb59cb63c 100644
--- a/src/solvers/smt1/smt1_conv.cpp
+++ b/src/solvers/smt1/smt1_conv.cpp
@@ -12,7 +12,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/expr_util.h>
 #include <util/std_types.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/fixedbv.h>
 #include <util/pointer_offset_size.h>
 #include <util/base_type.h>
@@ -674,7 +673,7 @@ std::string smt1_convt::convert_identifier(const irep_idt &identifier)
     else
     {
       dest+='.';
-      dest.append(i2string(ch));
+      dest.append(std::to_string(ch));
       dest+='.';
     }
   }
@@ -3259,7 +3258,7 @@ void smt1_convt::find_symbols(const exprt &expr)
   {
     if(array_of_map.find(expr)==array_of_map.end())
     {
-      irep_idt id="array_of'"+i2string(array_of_map.size());
+      irep_idt id="array_of'"+std::to_string(array_of_map.size());
       out << "; the following is a poor substitute for lambda i. x" << "\n";
       out << ":extrafuns(("
           << id
@@ -3296,7 +3295,7 @@ void smt1_convt::find_symbols(const exprt &expr)
     if(array_expr_map.find(expr)==array_expr_map.end())
     {
       // introduce a temporary array.
-      irep_idt id="array_init'"+i2string(array_expr_map.size());
+      irep_idt id="array_init'"+std::to_string(array_expr_map.size());
       out << ":extrafuns(("
           << id
           << " ";
@@ -3313,7 +3312,7 @@ void smt1_convt::find_symbols(const exprt &expr)
       string2array_map[expr]=t;
 
       // introduce a temporary array.
-      irep_idt id="string'"+i2string(array_expr_map.size());
+      irep_idt id="string'"+std::to_string(array_expr_map.size());
       out << ":extrafuns(("
           << id
           << " ";
diff --git a/src/solvers/smt1/smt1_conv.h b/src/solvers/smt1/smt1_conv.h
index 8785f3f70c0..a51eb8bd438 100644
--- a/src/solvers/smt1/smt1_conv.h
+++ b/src/solvers/smt1/smt1_conv.h
@@ -13,7 +13,6 @@ Revision: Roberto Bruttomesso, roberto.bruttomesso@unisi.ch
 #include <sstream>
 #include <set>
 
-#include <util/hash_cont.h>
 #include <util/std_expr.h>
 
 #include <solvers/prop/prop_conv.h>
@@ -155,7 +154,7 @@ class smt1_convt:public prop_convt
       identifier.value=tmp;
   }
 
-  typedef hash_map_cont<irep_idt, identifiert, irep_id_hash>
+  typedef std::unordered_map<irep_idt, identifiert, irep_id_hash>
     identifier_mapt;
 
   identifier_mapt identifier_map;
diff --git a/src/solvers/smt1/smt1_dec.cpp b/src/solvers/smt1/smt1_dec.cpp
index 66a62a34234..ee1615ad48b 100644
--- a/src/solvers/smt1/smt1_dec.cpp
+++ b/src/solvers/smt1/smt1_dec.cpp
@@ -21,7 +21,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/std_types.h>
 #include <util/tempfile.h>
 #include <util/arith_tools.h>
-#include <util/i2string.h>
 #include <util/string2int.h>
 #include <util/prefix.h>
 
@@ -251,7 +250,7 @@ decision_proceduret::resultt smt1_dect::read_result_boolector(std::istream &in)
     boolean_assignment.clear();
     boolean_assignment.resize(no_boolean_variables, false);
 
-    typedef hash_map_cont<std::string, valuet, string_hash> valuest;
+    typedef std::unordered_map<std::string, valuet, string_hash> valuest;
     valuest values;
 
     while(std::getline(in, line))
@@ -306,7 +305,7 @@ decision_proceduret::resultt smt1_dect::read_result_boolector(std::istream &in)
 
     for(unsigned v=0; v<no_boolean_variables; v++)
     {
-      std::string value=values["B"+i2string(v)].value;
+      std::string value=values["B"+std::to_string(v)].value;
       if(value=="") continue;
       boolean_assignment[v]=(value=="1");
     }
@@ -418,7 +417,7 @@ decision_proceduret::resultt smt1_dect::read_result_mathsat(std::istream &in)
   boolean_assignment.clear();
   boolean_assignment.resize(no_boolean_variables, false);
 
-  typedef hash_map_cont<std::string, valuet, string_hash> valuest;
+  typedef std::unordered_map<std::string, valuet, string_hash> valuest;
   valuest values;
 
   while(std::getline(in, line))
@@ -471,7 +470,7 @@ decision_proceduret::resultt smt1_dect::read_result_mathsat(std::istream &in)
   // Booleans
   for(unsigned v=0; v<no_boolean_variables; v++)
   {
-    std::string value=values["B"+i2string(v)].value;
+    std::string value=values["B"+std::to_string(v)].value;
     if(value=="") continue;
     boolean_assignment[v]=(value=="true");
   }
@@ -499,7 +498,7 @@ decision_proceduret::resultt smt1_dect::read_result_z3(std::istream &in)
   boolean_assignment.clear();
   boolean_assignment.resize(no_boolean_variables, false);
 
-  typedef hash_map_cont<std::string, std::string, string_hash> valuest;
+  typedef std::unordered_map<std::string, std::string, string_hash> valuest;
   valuest values;
 
   while(std::getline(in, line))
@@ -537,7 +536,7 @@ decision_proceduret::resultt smt1_dect::read_result_z3(std::istream &in)
   // Booleans
   for(unsigned v=0; v<no_boolean_variables; v++)
   {
-    std::string value=values["B"+i2string(v)];
+    std::string value=values["B"+std::to_string(v)];
     if(value=="") continue;
     boolean_assignment[v]=(value=="true");
   }
@@ -688,7 +687,7 @@ decision_proceduret::resultt smt1_dect::read_result_cvc3(std::istream &in)
   boolean_assignment.clear();
   boolean_assignment.resize(no_boolean_variables, false);
 
-  typedef hash_map_cont<std::string, std::string, string_hash> valuest;
+  typedef std::unordered_map<std::string, std::string, string_hash> valuest;
   valuest values;
 
   while(std::getline(in, line))
@@ -786,7 +785,7 @@ decision_proceduret::resultt smt1_dect::read_result_cvc3(std::istream &in)
   // Booleans
   for(unsigned v=0; v<no_boolean_variables; v++)
   {
-    std::string value=values["B"+i2string(v)];
+    std::string value=values["B"+std::to_string(v)];
     if(value=="") continue;
     boolean_assignment[v]=(value=="true");
   }
diff --git a/src/solvers/smt1/smt1_prop.cpp b/src/solvers/smt1/smt1_prop.cpp
index ff30765775b..6a9b0dd73b5 100644
--- a/src/solvers/smt1/smt1_prop.cpp
+++ b/src/solvers/smt1/smt1_prop.cpp
@@ -10,7 +10,6 @@ Revisions: Roberto Bruttomesso, roberto.bruttomesso@unisi.ch
 
 #include <cassert>
 
-#include <util/i2string.h>
 
 #include "smt1_prop.h"
 
@@ -442,7 +441,7 @@ std::string smt1_propt::smt1_literal(literalt l)
   else if(l==const_literal(true))
     return "true";
 
-  std::string v="B"+i2string(l.var_no());
+  std::string v="B"+std::to_string(l.var_no());
 
   if(l.sign())
     return "(not "+v+")";
diff --git a/src/solvers/smt2/smt2_conv.cpp b/src/solvers/smt2/smt2_conv.cpp
index 5d83d2de701..1f66f7920dc 100644
--- a/src/solvers/smt2/smt2_conv.cpp
+++ b/src/solvers/smt2/smt2_conv.cpp
@@ -12,7 +12,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/expr_util.h>
 #include <util/std_types.h>
 #include <util/std_expr.h>
-#include <util/i2string.h>
 #include <util/fixedbv.h>
 #include <util/pointer_offset_size.h>
 #include <util/ieee_float.h>
@@ -928,7 +927,7 @@ void smt2_convt::convert_literal(const literalt l)
     if(l.sign())
       out << ")";
 
-    smt2_identifiers.insert("B"+i2string(l.var_no()));
+    smt2_identifiers.insert("B"+std::to_string(l.var_no()));
   }
 }
 
@@ -962,7 +961,7 @@ std::string smt2_convt::convert_identifier(const irep_idt &identifier)
     case '\\':
     case '&': // we use the & for escaping
       result+='&';
-      result+=i2string(ch);
+      result+=std::to_string(ch);
       result+=';';
       break;
 
@@ -992,19 +991,19 @@ std::string smt2_convt::type2id(const typet &type) const
   if(type.id()==ID_floatbv)
   {
     ieee_float_spect spec(to_floatbv_type(type));
-    return "f"+i2string(spec.width())+"_"+i2string(spec.f);
+    return "f"+std::to_string(spec.width())+"_"+std::to_string(spec.f);
   }
   else if(type.id()==ID_unsignedbv)
   {
-    return "u"+i2string(to_unsignedbv_type(type).get_width());
+    return "u"+std::to_string(to_unsignedbv_type(type).get_width());
   }
   else if(type.id()==ID_c_bool)
   {
-    return "u"+i2string(to_c_bool_type(type).get_width());
+    return "u"+std::to_string(to_c_bool_type(type).get_width());
   }
   else if(type.id()==ID_signedbv)
   {
-    return "s"+i2string(to_signedbv_type(type).get_width());
+    return "s"+std::to_string(to_signedbv_type(type).get_width());
   }
   else if(type.id()==ID_bool)
   {
@@ -4618,7 +4617,7 @@ void smt2_convt::find_symbols(const exprt &expr)
   {
     if(defined_expressions.find(expr)==defined_expressions.end())
     {
-      irep_idt id="array_of."+i2string(defined_expressions.size());
+      irep_idt id="array_of."+std::to_string(defined_expressions.size());
       out << "; the following is a substitute for lambda i. x" << "\n";
       out << "(declare-fun " << id << " () ";
       convert_type(expr.type());
@@ -4642,7 +4641,7 @@ void smt2_convt::find_symbols(const exprt &expr)
     {
       const array_typet &array_type=to_array_type(expr.type());
 
-      irep_idt id="array."+i2string(defined_expressions.size());
+      irep_idt id="array."+std::to_string(defined_expressions.size());
       out << "; the following is a substitute for an array constructor" << "\n";
       out << "(declare-fun " << id << " () ";
       convert_type(array_type);
@@ -4668,7 +4667,7 @@ void smt2_convt::find_symbols(const exprt &expr)
       exprt tmp=to_string_constant(expr).to_array_expr();
       const array_typet &array_type=to_array_type(tmp.type());
 
-      irep_idt id="string."+i2string(defined_expressions.size());
+      irep_idt id="string."+std::to_string(defined_expressions.size());
       out << "; the following is a substitute for a string" << "\n";
       out << "(declare-fun " << id << " () ";
       convert_type(array_type);
@@ -4696,7 +4695,7 @@ void smt2_convt::find_symbols(const exprt &expr)
     {
       if (object_sizes.find(expr)==object_sizes.end())
       {
-        irep_idt id="object_size."+i2string(object_sizes.size());
+        irep_idt id="object_size."+std::to_string(object_sizes.size());
         out << "(declare-fun " << id << " () ";
         convert_type(expr.type());
         out << ")" << "\n";
@@ -4753,7 +4752,7 @@ void smt2_convt::find_symbols(const exprt &expr)
       exprt tmp1=expr;
       for(unsigned i=0; i<tmp1.operands().size(); i++)
         tmp1.operands()[i]=
-          smt2_symbolt("op"+i2string(i), tmp1.operands()[i].type());
+          smt2_symbolt("op"+std::to_string(i), tmp1.operands()[i].type());
 
       exprt tmp2=float_bv(tmp1);
       tmp2=letify(tmp2);
@@ -5015,7 +5014,7 @@ void smt2_convt::find_symbols_rec(
      if(use_datatypes &&
         datatype_map.find(type)==datatype_map.end())
      {
-       std::string smt_typename = "complex."+i2string(datatype_map.size());
+       std::string smt_typename = "complex."+std::to_string(datatype_map.size());
        datatype_map[type] = smt_typename;
 
        out << "(declare-datatypes () ((" << smt_typename << " "
@@ -5045,7 +5044,7 @@ void smt2_convt::find_symbols_rec(
        if(to_integer(vector_type.size(), size))
          INVALIDEXPR("failed to convert vector size to constant");
 
-       std::string smt_typename = "vector."+i2string(datatype_map.size());
+       std::string smt_typename = "vector."+std::to_string(datatype_map.size());
        datatype_map[type] = smt_typename;
 
        out << "(declare-datatypes () ((" << smt_typename << " "
@@ -5068,7 +5067,7 @@ void smt2_convt::find_symbols_rec(
      if(use_datatypes &&
         datatype_map.find(type)==datatype_map.end())
      {
-       std::string smt_typename = "struct."+i2string(datatype_map.size());
+       std::string smt_typename = "struct."+std::to_string(datatype_map.size());
        datatype_map[type] = smt_typename;
        need_decl=true;
      }
@@ -5278,7 +5277,7 @@ void smt2_convt::collect_bindings(
   assert(map.find(expr) == map.end());
 
   symbol_exprt let=
-    symbol_exprt("_let_"+i2string(++let_id_count), expr.type());
+    symbol_exprt("_let_"+std::to_string(++let_id_count), expr.type());
 
   map.insert(std::make_pair(expr, std::make_pair(1, let)));
 
diff --git a/src/solvers/smt2/smt2_conv.h b/src/solvers/smt2/smt2_conv.h
index cd82485d875..3e27a1500d0 100644
--- a/src/solvers/smt2/smt2_conv.h
+++ b/src/solvers/smt2/smt2_conv.h
@@ -12,7 +12,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <sstream>
 #include <set>
 
-#include <util/hash_cont.h>
 #include <util/std_expr.h>
 #include <util/byte_operators.h>
 
@@ -165,7 +164,7 @@ class smt2_convt:public prop_convt
 
   // letification
   typedef std::pair<unsigned, symbol_exprt> let_count_id;
-  typedef hash_map_cont<exprt, let_count_id, irep_hash> seen_expressionst;
+  typedef std::unordered_map<exprt, let_count_id, irep_hash> seen_expressionst;
   unsigned let_id_count;
   const static unsigned LET_COUNT = 2;
 
@@ -265,7 +264,7 @@ class smt2_convt:public prop_convt
     }
   };
 
-  typedef hash_map_cont<irep_idt, identifiert, irep_id_hash>
+  typedef std::unordered_map<irep_idt, identifiert, irep_id_hash>
     identifier_mapt;
 
   identifier_mapt identifier_map;
diff --git a/src/solvers/smt2/smt2_dec.cpp b/src/solvers/smt2/smt2_dec.cpp
index 362d18ece96..722a6b43bee 100644
--- a/src/solvers/smt2/smt2_dec.cpp
+++ b/src/solvers/smt2/smt2_dec.cpp
@@ -21,7 +21,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/std_types.h>
 #include <util/tempfile.h>
 #include <util/arith_tools.h>
-#include <util/i2string.h>
 #include <util/ieee_float.h>
 
 #include "smt2_dec.h"
@@ -238,7 +237,7 @@ decision_proceduret::resultt smt2_dect::read_result(std::istream &in)
   boolean_assignment.clear();
   boolean_assignment.resize(no_boolean_variables, false);
 
-  typedef hash_map_cont<irep_idt, irept, irep_id_hash> valuest;
+  typedef std::unordered_map<irep_idt, irept, irep_id_hash> valuest;
   valuest values;
 
   while(in)
@@ -290,7 +289,7 @@ decision_proceduret::resultt smt2_dect::read_result(std::istream &in)
   // Booleans
   for(unsigned v=0; v<no_boolean_variables; v++)
   {
-    const irept &value=values["B"+i2string(v)];
+    const irept &value=values["B"+std::to_string(v)];
     boolean_assignment[v]=(value.id()==ID_true);
   }
 
diff --git a/src/solvers/smt2/smt2_prop.cpp b/src/solvers/smt2/smt2_prop.cpp
index ffaec5058c0..060f5848501 100644
--- a/src/solvers/smt2/smt2_prop.cpp
+++ b/src/solvers/smt2/smt2_prop.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
-#include <util/i2string.h>
 
 #include "smt2_prop.h"
 
@@ -489,7 +488,7 @@ std::string smt2_propt::smt2_literal(literalt l)
   else if(l==const_literal(true))
     return "true";
 
-  std::string v="B"+i2string(l.var_no());
+  std::string v="B"+std::to_string(l.var_no());
 
   smt2_identifiers.insert(v);
 
diff --git a/src/symex/symex_cover.cpp b/src/symex/symex_cover.cpp
index 3f907a67477..2b4f88c6afc 100644
--- a/src/symex/symex_cover.cpp
+++ b/src/symex/symex_cover.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <iostream>
 
-#include <util/i2string.h>
 #include <util/json_expr.h>
 #include <util/xml_expr.h>
 
@@ -191,8 +190,8 @@ void symex_parse_optionst::report_cover(
           }
         }
       }
-      json_result["totalGoals"]=json_numbert(i2string(property_map.size()));
-      json_result["goalsCovered"]=json_numbert(i2string(goals_covered));
+      json_result["totalGoals"]=json_numbert(std::to_string(property_map.size()));
+      json_result["goalsCovered"]=json_numbert(std::to_string(goals_covered));
       std::cout << ",\n" << json_result;
       break;
     }
diff --git a/src/util/Makefile b/src/util/Makefile
index 2fddfa618bb..f98b6588df8 100644
--- a/src/util/Makefile
+++ b/src/util/Makefile
@@ -1,5 +1,5 @@
 SRC = arith_tools.cpp base_type.cpp cmdline.cpp config.cpp symbol_table.cpp \
-      expr.cpp expr_util.cpp i2string.cpp irep.cpp language.cpp \
+      expr.cpp expr_util.cpp irep.cpp language.cpp \
       lispexpr.cpp lispirep.cpp source_location.cpp message.cpp language_file.cpp \
       mp_arith.cpp namespace.cpp parse_options.cpp rename.cpp \
       replace_expr.cpp threeval.cpp typecheck.cpp graph.cpp \
@@ -9,7 +9,7 @@ SRC = arith_tools.cpp base_type.cpp cmdline.cpp config.cpp symbol_table.cpp \
       simplify_expr_array.cpp simplify_expr_struct.cpp \
       simplify_expr_boolean.cpp simplify_expr_pointer.cpp \
       get_module.cpp string_hash.cpp string_container.cpp identifier.cpp \
-      rational.cpp options.cpp c_misc.cpp dstring.cpp \
+      rational.cpp options.cpp dstring.cpp \
       find_symbols.cpp rational_tools.cpp ui_message.cpp simplify_utils.cpp \
       time_stopping.cpp symbol.cpp irep_hash_container.cpp cout_message.cpp \
       type_eq.cpp guard.cpp array_name.cpp message_stream.cpp \
diff --git a/src/util/config.cpp b/src/util/config.cpp
index 6ffbd3505f0..48021c5754a 100644
--- a/src/util/config.cpp
+++ b/src/util/config.cpp
@@ -14,7 +14,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include "arith_tools.h"
 #include "cmdline.h"
 #include "simplify_expr.h"
-#include "i2string.h"
 #include "std_expr.h"
 #include "cprover_prefix.h"
 
@@ -539,7 +538,7 @@ void configt::ansi_ct::set_arch_spec_mips(const irep_idt &subarch)
   case flavourt::GCC:
     defines.push_back("__mips__");
     defines.push_back("mips");
-    defines.push_back("_MIPS_SZPTR="+i2string(config.ansi_c.pointer_width));
+    defines.push_back("_MIPS_SZPTR="+std::to_string(config.ansi_c.pointer_width));
     break;
 
   case flavourt::VISUAL_STUDIO:
diff --git a/src/util/endianness_map.h b/src/util/endianness_map.h
index 4d5fd9825b6..efb09f195c0 100644
--- a/src/util/endianness_map.h
+++ b/src/util/endianness_map.h
@@ -17,11 +17,11 @@ Author: Daniel Kroening, kroening@kroening.com
 */
 
 #include <cassert>
+#include <iosfwd>
 #include <vector>
 
-#include "expr.h"
-
 class namespacet;
+class typet;
 
 /*! \brief Maps a big-endian offset to a little-endian offset
 */
diff --git a/src/util/expr_util.cpp b/src/util/expr_util.cpp
index 63e57aa3640..135f64a6313 100644
--- a/src/util/expr_util.cpp
+++ b/src/util/expr_util.cpp
@@ -197,67 +197,6 @@ exprt gen_one(const typet &type)
 
 /*******************************************************************\
 
-Function: gen_not
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-exprt gen_unary(const irep_idt &id, const typet &type, const exprt &op);
-
-exprt gen_not(const exprt &op)
-{
-  return gen_unary(ID_not, bool_typet(), op);
-}
-
-/*******************************************************************\
-
-Function: gen_unary
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-exprt gen_unary(const irep_idt &id, const typet &type, const exprt &op)
-{
-  exprt result(id, type);
-  result.copy_to_operands(op);
-  return result;
-}
-
-/*******************************************************************\
-
-Function: gen_binary
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-exprt gen_binary(
-  const irep_idt &id,
-  const typet &type,
-  const exprt &op1,
-  const exprt &op2)
-{
-  exprt result(id, type);
-  result.copy_to_operands(op1, op2);
-  return result;
-}
-
-/*******************************************************************\
-
 Function: make_next_state
 
   Inputs:
diff --git a/src/util/expr_util.h b/src/util/expr_util.h
index 513b7cfb342..95430d563ce 100644
--- a/src/util/expr_util.h
+++ b/src/util/expr_util.h
@@ -33,13 +33,6 @@ class namespacet;
 exprt gen_zero(const typet &type);
 /*! \copydoc gen_zero(const typet &) */
 exprt gen_one(const typet &type);
-/*! \copydoc gen_zero(const typet &) */
-exprt gen_not_old(const exprt &op);
-
-/*! \copydoc gen_zero(const typet &) */
-void gen_and_old(exprt &expr);
-/*! \copydoc gen_zero(const typet &) */
-void gen_or_old(exprt &expr);
 
 /*! \copydoc gen_zero(const typet &) */
 void make_next_state(exprt &);
diff --git a/src/util/find_macros.h b/src/util/find_macros.h
index 86f56e2ef8c..17b8282502c 100644
--- a/src/util/find_macros.h
+++ b/src/util/find_macros.h
@@ -9,13 +9,14 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_UTIL_FIND_MACROS_H
 #define CPROVER_UTIL_FIND_MACROS_H
 
-#include "hash_cont.h"
+#include <unordered_set>
+
 #include "irep.h"
 
 class exprt;
 class namespacet;
 
-typedef hash_set_cont<irep_idt, irep_id_hash> find_macros_sett;
+typedef std::unordered_set<irep_idt, irep_id_hash> find_macros_sett;
 
 void find_macros(
   const exprt &src,
diff --git a/src/util/find_symbols.h b/src/util/find_symbols.h
index 6f53cdc21b1..4ca899e4b40 100644
--- a/src/util/find_symbols.h
+++ b/src/util/find_symbols.h
@@ -10,15 +10,15 @@ Author: Daniel Kroening, kroening@kroening.com
 #define CPROVER_UTIL_FIND_SYMBOLS_H
 
 #include <set>
+#include <unordered_set>
 
-#include "hash_cont.h"
 #include "irep.h"
 
 class exprt;
 class symbol_exprt;
 class typet;
 
-typedef hash_set_cont<irep_idt, irep_id_hash> find_symbols_sett;
+typedef std::unordered_set<irep_idt, irep_id_hash> find_symbols_sett;
 
 void find_symbols(
   const exprt &src,
diff --git a/src/util/gcd.cpp b/src/util/gcd.cpp
deleted file mode 100644
index baabead7436..00000000000
--- a/src/util/gcd.cpp
+++ /dev/null
@@ -1,49 +0,0 @@
-/*******************************************************************\
-
-Module:
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#include <cassert>
-
-#include "gcd.h"
-
-/*******************************************************************\
-
-Function: gcd
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-#if 0
-mp_integer gcd(const mp_integer &_a, const mp_integer &_b)
-{
-  mp_integer a=_a, b=_b;
-
-  if(a.is_negative()) a.negate();
-  if(b.is_negative()) b.negate();
-
-  if(a==1) return a;
-  if(b==1) return b;
-  if(a==b) return a;
-
-  while(!b.is_zero())
-  {
-    mp_integer tmp_b=b;
-    b=a%b;
-    assert(b<tmp_b); // make progress
-    a=tmp_b;
-  }
-
-  assert(!a.is_negative());
-
-  return a;
-}
-#endif
diff --git a/src/util/gcd.h b/src/util/gcd.h
deleted file mode 100644
index 1c23bb1e483..00000000000
--- a/src/util/gcd.h
+++ /dev/null
@@ -1,16 +0,0 @@
-/*******************************************************************\
-
-Module:
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#ifndef CPROVER_UTIL_GCD_H
-#define CPROVER_UTIL_GCD_H
-
-#include "mp_arith.h"
-
-//mp_integer gcd(const mp_integer &a, const mp_integer &b);
-
-#endif // CPROVER_UTIL_GCD_H
diff --git a/src/util/get_module.cpp b/src/util/get_module.cpp
index 361728e4be3..6f1ea627967 100644
--- a/src/util/get_module.cpp
+++ b/src/util/get_module.cpp
@@ -6,12 +6,23 @@ Author: Daniel Kroening, kroening@kroening.com
 
 \*******************************************************************/
 
+#include <list>
 #include <set>
 
 #include "get_module.h"
 #include "message.h"
 #include "symbol_table.h"
 
+typedef std::list<const symbolt *> symbolptr_listt;
+
+#define forall_symbolptr_list(it, list) \
+  for(symbolptr_listt::const_iterator it=(list).begin(); \
+      it!=(list).end(); ++it)
+
+#define Forall_symbolptr_list(it, list) \
+  for(symbolptr_listt::iterator it=(list).begin(); \
+      it!=(list).end(); ++it)
+
 /*******************************************************************\
 
 Function: get_module_by_name
diff --git a/src/util/guard.cpp b/src/util/guard.cpp
index 4ca0b0fd2b6..e5362143018 100644
--- a/src/util/guard.cpp
+++ b/src/util/guard.cpp
@@ -285,6 +285,10 @@ Function: guardt::is_false
 
 \*******************************************************************/
 
+#define forall_guard(it, guard_list) \
+  for(guardt::guard_listt::const_iterator it=(guard_list).begin(); \
+      it!=(guard_list).end(); ++it)
+
 bool guardt::is_false() const
 {
   forall_guard(it, guard_list)
diff --git a/src/util/guard.h b/src/util/guard.h
index 8a8508520fd..7344fc10d2e 100644
--- a/src/util/guard.h
+++ b/src/util/guard.h
@@ -88,14 +88,4 @@ class guardt:public exprt
 #endif
 };
 
-#if 0
-#define Forall_guard(it, guard_list) \
-  for(guardt::guard_listt::iterator it=(guard_list).begin(); \
-      it!=(guard_list).end(); ++it)
-
-#define forall_guard(it, guard_list) \
-  for(guardt::guard_listt::const_iterator it=(guard_list).begin(); \
-      it!=(guard_list).end(); ++it)
-#endif
-
 #endif // CPROVER_UTIL_GUARD_H
diff --git a/src/util/hash_cont.h b/src/util/hash_cont.h
deleted file mode 100644
index d6365bab7b1..00000000000
--- a/src/util/hash_cont.h
+++ /dev/null
@@ -1,93 +0,0 @@
-/*******************************************************************\
-
-Module: STL Hash map / set
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#ifndef CPROVER_UTIL_HASH_CONT_H
-#define CPROVER_UTIL_HASH_CONT_H
-
-// You need to pick one of the following options:
-//
-// #define STL_HASH_NONE
-// #define STL_HASH_STDEXT
-// #define STL_HASH_GNU
-// #define STL_HASH_TR1
-// #define STL_HASH_STD
-//
-// The default is 'STL_HASH_STD'. This file will go away one day.
-
-#if !defined(STL_HASH_NONE) && !defined(STL_HASH_STDEXT) && \
-    !defined(STL_HASH_GNU) && !defined(STL_HASH_TR1) && \
-    !defined(STL_HASH_STD)
-#define STL_HASH_STD
-#endif
-
-#if defined(STL_HASH_NONE)
-
-#include <map>
-#include <set>
-
-template<class T1, class T2, class T3>
-typedef std::map<T1, T2> hash_map_cont;
-
-template<class T1, class T2>
-typedef std::set<T1> hash_set_cont;
-
-template<class T1, class T2>
-typedef std::multiset<T1> hash_multiset_cont;
-
-#elif defined(STL_HASH_STDEXT)
-
-#include <hash_map>
-#include <hash_set>
-
-// for Visual Studio >= 2003
-
-#define hash_map_cont stdext::hash_map
-#define hash_set_cont stdext::hash_set
-#define hash_multiset_cont stdext::hash_multiset
-
-#elif defined(STL_HASH_GNU)
-
-#include <ext/hash_map>
-#include <ext/hash_set>
-
-// for new g++ libraries >= 3.2
-
-#define hash_map_cont __gnu_cxx::hash_map
-#define hash_set_cont __gnu_cxx::hash_set
-#define hash_multiset_cont __gnu_cxx::hash_multiset
-
-#elif defined(STL_HASH_TR1)
-
-#ifdef _MSC_VER
-#include <unordered_set>
-#include <unordered_map>
-#else
-#include <tr1/unordered_set>
-#include <tr1/unordered_map>
-#endif
-
-#define hash_map_cont std::tr1::unordered_map
-#define hash_set_cont std::tr1::unordered_set
-#define hash_multiset_cont std::tr1::unordered_multiset
-
-#elif defined(STL_HASH_STD)
-
-#include <unordered_set>
-#include <unordered_map>
-
-#define hash_map_cont std::unordered_map
-#define hash_set_cont std::unordered_set
-#define hash_multiset_cont std::unordered_multiset
-
-#else
-
-#error Please select hash container option
-
-#endif
-
-#endif // CPROVER_UTIL_HASH_CONT_H
diff --git a/src/util/i2string.cpp b/src/util/i2string.cpp
deleted file mode 100644
index 597c7b098a5..00000000000
--- a/src/util/i2string.cpp
+++ /dev/null
@@ -1,186 +0,0 @@
-/*******************************************************************\
-
-Module:
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#define USE_SPRINTF
-
-#ifdef USE_SPRINTF
-
-#include <cstdio>
-#include <cstring>
-
-#include "i2string.h"
-
-#ifdef _WIN32
-#ifndef __MINGW32__
-#define snprintf sprintf_s
-#endif
-#endif
-
-#include <sstream>
-
-#include "i2string.h"
-
-#endif
-
-/*******************************************************************\
-
-Function: i2string
-
-  Inputs: signed integer
-
- Outputs: string class
-
- Purpose: convert signed integer to string class
-
-\*******************************************************************/
-
-std::string i2string(int i)
-{
-  #ifdef USE_SPRINTF
-  char buffer[100];
-  snprintf(buffer, sizeof(buffer), "%d", i);
-  return buffer;
-  #else
-  std::ostringstream strInt;
-  strInt << i;
-  return strInt.str();
-  #endif
-}
-
-/*******************************************************************\
-
-Function: i2string
-
-  Inputs: signed long integer
-
- Outputs: string class
-
- Purpose: convert signed integer to string class
-
-\*******************************************************************/
-
-std::string i2string(signed long int i)
-{
-  #ifdef USE_SPRINTF
-  char buffer[100];
-  snprintf(buffer, sizeof(buffer), "%ld", i);
-  return buffer;
-  #else
-  std::ostringstream strInt;
-  strInt << i;
-  return strInt.str();
-  #endif
-}
-
-/*******************************************************************\
-
-Function: i2string
-
-  Inputs: unsigned integer
-
- Outputs: string class
-
- Purpose: convert unsigned integer to string class
-
-\*******************************************************************/
-
-std::string i2string(unsigned i)
-{
-  #ifdef USE_SPRINTF
-  char buffer[100];
-  snprintf(buffer, sizeof(buffer), "%u", i);
-  return buffer;
-  #else
-  std::ostringstream strInt;
-  strInt << i;
-  return strInt.str();
-  #endif
-}
-
-/*******************************************************************\
-
-Function: i2string
-
-  Inputs: unsigned long integer
-
- Outputs: string class
-
- Purpose: convert unsigned integer to string class
-
-\*******************************************************************/
-
-std::string i2string(unsigned long int i)
-{
-  #ifdef USE_SPRINTF
-  char buffer[100];
-  snprintf(buffer, sizeof(buffer), "%lu", i);
-  return buffer;
-  #else
-  std::ostringstream strInt;
-  strInt << i;
-  return strInt.str();
-  #endif
-}
-
-/*******************************************************************\
-
-Function: i2string
-
-  Inputs: signed long long
-
- Outputs: string class
-
- Purpose: convert signed integer to string class
-
-\*******************************************************************/
-
-std::string i2string(signed long long i)
-{
-  #ifdef USE_SPRINTF
-  char buffer[100];
-  snprintf(buffer, sizeof(buffer), "%lld", i);
-  return buffer;
-  #else
-  std::ostringstream strInt;
-
-  strInt << i;
-  std::string str;
-  strstream2string(strInt, str);
-
-  return str;
-  #endif
-}
-
-/*******************************************************************\
-
-Function: i2string
-
-  Inputs: unsigned long long
-
- Outputs: string class
-
- Purpose: convert unsigned integer to string class
-
-\*******************************************************************/
-
-std::string i2string(unsigned long long i)
-{
-  #ifdef USE_SPRINTF
-  char buffer[100];
-  snprintf(buffer, sizeof(buffer), "%llu", i);
-  return buffer;
-  #else
-  std::ostringstream strInt;
-
-  strInt << i;
-  std::string str;
-  strstream2string(strInt, str);
-
-  return str;
-  #endif
-}
diff --git a/src/util/i2string.h b/src/util/i2string.h
deleted file mode 100644
index 71f8eafbab0..00000000000
--- a/src/util/i2string.h
+++ /dev/null
@@ -1,23 +0,0 @@
-/*******************************************************************\
-
-Module:
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#ifndef CPROVER_UTIL_I2STRING_H
-#define CPROVER_UTIL_I2STRING_H
-
-#include <string>
-
-// One day, the below will be replaced by C++11's std::to_string.
-
-std::string i2string(int i);
-std::string i2string(signed long int i);
-std::string i2string(signed long long int i);
-std::string i2string(unsigned int i);
-std::string i2string(unsigned long int i);
-std::string i2string(unsigned long long int i);
-
-#endif // CPROVER_UTIL_I2STRING_H
diff --git a/src/util/ieee_float.cpp b/src/util/ieee_float.cpp
index 57659139ae0..6ad3e417e39 100644
--- a/src/util/ieee_float.cpp
+++ b/src/util/ieee_float.cpp
@@ -18,7 +18,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include "std_types.h"
 #include "std_expr.h"
 #include "ieee_float.h"
-#include "i2string.h"
 
 /*******************************************************************\
 
diff --git a/src/util/irep.cpp b/src/util/irep.cpp
index ef67d57a32c..3adafe3d885 100644
--- a/src/util/irep.cpp
+++ b/src/util/irep.cpp
@@ -11,7 +11,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include "string2int.h"
 #include "irep.h"
-#include "i2string.h"
 #include "string_hash.h"
 #include "irep_hash.h"
 
@@ -426,7 +425,7 @@ Function: irept::set
 
 void irept::set(const irep_namet &name, const long long value)
 {
-  add(name).id(i2string(value));
+  add(name).id(std::to_string(value));
 }
 
 /*******************************************************************\
@@ -969,7 +968,7 @@ std::string irept::pretty(unsigned indent, unsigned max_indent) const
     result+="\n";
     indent_str(result, indent);
 
-    result+=i2string(count++);
+    result+=std::to_string(count++);
     result+=": ";
 
     result+=it->pretty(indent+2, max_indent);
diff --git a/src/util/irep_hash_container.h b/src/util/irep_hash_container.h
index 6e9025da16c..45894b9d79d 100644
--- a/src/util/irep_hash_container.h
+++ b/src/util/irep_hash_container.h
@@ -13,7 +13,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <vector>
 
 #include "numbering.h"
-#include "hash_cont.h"
 
 class irept;
 
@@ -45,7 +44,7 @@ class irep_hash_container_baset
     }
   };
 
-  typedef hash_map_cont<const void *, unsigned, pointer_hash> ptr_hasht;
+  typedef std::unordered_map<const void *, unsigned, pointer_hash> ptr_hasht;
   ptr_hasht ptr_hash;
 
   // this is the second level: content
diff --git a/src/util/json_expr.cpp b/src/util/json_expr.cpp
index 7fd4f265f3f..2986decd223 100644
--- a/src/util/json_expr.cpp
+++ b/src/util/json_expr.cpp
@@ -14,7 +14,6 @@ Author: Peter Schrammel
 #include "fixedbv.h"
 #include "std_expr.h"
 #include "config.h"
-#include "i2string.h"
 
 #include "json_expr.h"
 
@@ -74,28 +73,28 @@ json_objectt json(
   {
     result["name"]=json_stringt("integer");
     result["width"]=
-      json_numbert(i2string(to_unsignedbv_type(type).get_width()));
+      json_numbert(std::to_string(to_unsignedbv_type(type).get_width()));
   }
   else if(type.id()==ID_signedbv)
   {
     result["name"]=json_stringt("integer");
-    result["width"]=json_numbert(i2string(to_signedbv_type(type).get_width()));
+    result["width"]=json_numbert(std::to_string(to_signedbv_type(type).get_width()));
   }
   else if(type.id()==ID_floatbv)
   {
     result["name"]=json_stringt("float");
-    result["width"]=json_numbert(i2string(to_floatbv_type(type).get_width()));
+    result["width"]=json_numbert(std::to_string(to_floatbv_type(type).get_width()));
   }
   else if(type.id()==ID_bv)
   {
     result["name"]=json_stringt("integer");
-    result["width"]=json_numbert(i2string(to_bv_type(type).get_width()));
+    result["width"]=json_numbert(std::to_string(to_bv_type(type).get_width()));
   }
   else if(type.id()==ID_c_bit_field)
   {
     result["name"]=json_stringt("integer");
     result["width"]=
-      json_numbert(i2string(to_c_bit_field_type(type).get_width()));
+      json_numbert(std::to_string(to_c_bit_field_type(type).get_width()));
   }
   else if(type.id()==ID_c_enum_tag)
   {
@@ -105,7 +104,7 @@ json_objectt json(
   else if(type.id()==ID_fixedbv)
   {
     result["name"]=json_stringt("fixed");
-    result["width"]=json_numbert(i2string(to_fixedbv_type(type).get_width()));
+    result["width"]=json_numbert(std::to_string(to_fixedbv_type(type).get_width()));
   }
   else if(type.id()==ID_pointer)
   {
@@ -189,7 +188,7 @@ json_objectt json(
 
       result["name"]=json_stringt("integer");
       result["binary"]=json_stringt(expr.get_string(ID_value));
-      result["width"]=json_numbert(i2string(width));
+      result["width"]=json_numbert(std::to_string(width));
 
       const typet &underlying_type=
         type.id()==ID_c_bit_field?type.subtype():
@@ -281,7 +280,7 @@ json_objectt json(
     forall_operands(it, expr)
     {
       json_objectt &e=elements.push_back().make_object();
-      e["index"]=json_numbert(i2string(index));
+      e["index"]=json_numbert(std::to_string(index));
       e["value"]=json(*it, ns);
       index++;
     }
diff --git a/src/util/language_file.cpp b/src/util/language_file.cpp
index eaaa1ea00b2..f7a49991d63 100644
--- a/src/util/language_file.cpp
+++ b/src/util/language_file.cpp
@@ -8,7 +8,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <fstream>
 
-#include "i2string.h"
 #include "language.h"
 #include "language_file.h"
 
@@ -172,7 +171,7 @@ bool language_filest::typecheck(symbol_tablet &symbol_table)
 
       while(modulemap.find(module_name)!=modulemap.end())
       {
-        module_name=*mo_it+"#"+i2string(collision_counter);
+        module_name=*mo_it+"#"+std::to_string(collision_counter);
         collision_counter++;
       }
 
diff --git a/src/util/merge_irep.h b/src/util/merge_irep.h
index 647654386b4..a7f182e9b6b 100644
--- a/src/util/merge_irep.h
+++ b/src/util/merge_irep.h
@@ -9,8 +9,9 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_UTIL_MERGE_IREP_H
 #define CPROVER_UTIL_MERGE_IREP_H
 
+#include <unordered_set>
+
 #include "irep.h"
-#include "hash_cont.h"
 
 class merged_irept:public irept
 {
@@ -82,10 +83,10 @@ class merged_irepst
   }
 
 protected:
-  typedef hash_set_cont<merged_irept, merged_irep_hash> merged_irep_storet;
+  typedef std::unordered_set<merged_irept, merged_irep_hash> merged_irep_storet;
   merged_irep_storet merged_irep_store;
 
-  typedef hash_set_cont<to_be_merged_irept, to_be_merged_irep_hash> to_be_merged_irep_storet;
+  typedef std::unordered_set<to_be_merged_irept, to_be_merged_irep_hash> to_be_merged_irep_storet;
   to_be_merged_irep_storet to_be_merged_irep_store;
 
   const merged_irept &merged(const irept &);
@@ -101,7 +102,7 @@ class merge_irept
   void operator()(irept &);
 
 protected:
-  typedef hash_set_cont<irept, irep_hash> irep_storet;
+  typedef std::unordered_set<irept, irep_hash> irep_storet;
   irep_storet irep_store;
 
   const irept & merged(const irept &irep);
@@ -113,7 +114,7 @@ class merge_full_irept
   void operator()(irept &);
 
 protected:
-  typedef hash_set_cont<irept, irep_full_hash, irep_full_eq> irep_storet;
+  typedef std::unordered_set<irept, irep_full_hash, irep_full_eq> irep_storet;
   irep_storet irep_store;
 
   const irept& merged(const irept &irep);
diff --git a/src/util/message.cpp b/src/util/message.cpp
index c1f0e36df18..bf2ef47e092 100644
--- a/src/util/message.cpp
+++ b/src/util/message.cpp
@@ -7,7 +7,6 @@ Author: Daniel Kroening, kroening@kroening.com
 \*******************************************************************/
 
 #include "message.h"
-#include "i2string.h"
 
 /*******************************************************************\
 
diff --git a/src/util/namespace.cpp b/src/util/namespace.cpp
index 1222fddffb6..1c18d29da96 100644
--- a/src/util/namespace.cpp
+++ b/src/util/namespace.cpp
@@ -37,7 +37,8 @@ unsigned get_max(
   forall_symbols(it, symbols)
     if(has_prefix(id2string(it->first), prefix))
       max_nr=
-        std::max(unsafe_c_str2unsigned(it->first.c_str()+prefix.size()),
+        std::max(unsafe_string2unsigned(
+                  id2string(it->first).substr(prefix.size())),
                  max_nr);
 
   return max_nr;
diff --git a/src/util/namespace_utils.h b/src/util/namespace_utils.h
deleted file mode 100644
index 3cbf117fd1c..00000000000
--- a/src/util/namespace_utils.h
+++ /dev/null
@@ -1,104 +0,0 @@
-/*******************************************************************\
-
-Module:
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-// THIS FILE IS DEPRECATED
-
-#ifndef CPROVER_UTIL_NAMESPACE_UTILS_H
-#define CPROVER_UTIL_NAMESPACE_UTILS_H
-
-#include "namespace.h"
-#include "base_type.h"
-#include "type_eq.h"
-#include "std_expr.h"
-
-// second: true <=> not found
-
-class namespace_utils_baset
-{
- public:
-  virtual ~namespace_utils_baset()
-  {
-  }
-
-  const symbolt &lookup(const irep_idt &name) const
-  {
-    const symbolt *symbol;
-    if(lookup(name, symbol))
-      throw "identifier "+id2string(name)+" not found";
-    return *symbol;
-  }
-
-  const symbolt &lookup(const symbol_exprt &symbol_expr) const
-  {
-    const symbolt *symbol;
-    if(lookup(symbol_expr.get_identifier(), symbol))
-      throw "identifier "+id2string(symbol_expr.get_identifier())+" not found";
-    return *symbol;
-  }
-
-  bool lookup(const irep_idt &name, const symbolt *&symbol) const
-  {
-    return ns().lookup(name, symbol);
-  }
-
-  bool lookup_symbol(const exprt &symbol_expr, const symbolt *&symbol) const
-  {
-    return ns().lookup(symbol_expr.get(ID_identifier), symbol);
-  }
-
-  void follow_symbol(irept &irep) const
-  {
-    ns().follow_symbol(irep);
-  }
-
-  void follow_macros(exprt &expr) const
-  {
-    ns().follow_macros(expr);
-  }
-
-  /*
-  void base_type(typet &type)
-  {
-    ::base_type(type, ns());
-  }
-
-  void base_type(exprt &expr)
-  {
-    ::base_type(expr, ns());
-  }
-  */
-
-  bool type_eq(const typet &type1, const typet &type2)
-  {
-    return ::type_eq(type1, type2, ns());
-  }
-
-  bool base_type_eq(const typet &type1, const typet &type2)
-  {
-    return ::base_type_eq(type1, type2, ns());
-  }
-
- protected:
-  virtual const namespacet &ns() const=0;
-};
-
-class namespace_utilst:public virtual namespace_utils_baset
-{
- public:
-  namespace_utilst(const namespacet &_ns):__ns(_ns){}
-
- protected:
-  const namespacet &__ns;
-
-  virtual const namespacet &ns() const
-  {
-    return __ns;
-  }
-};
-
-#endif // CPROVER_UTIL_NAMESPACE_UTILS_H
diff --git a/src/util/numbering.h b/src/util/numbering.h
index d4fccd81e9d..23aabfce0f2 100644
--- a/src/util/numbering.h
+++ b/src/util/numbering.h
@@ -11,9 +11,9 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 #include <map>
+#include <unordered_map>
 #include <vector>
 
-#include "hash_cont.h"
 
 template <typename T>
 class numbering:public std::vector<T>
@@ -108,7 +108,7 @@ class hash_numbering:public std::vector<T>
 protected:
   typedef std::vector<T> subt;
 
-  typedef hash_map_cont<T, number_type, hash_fkt> numberst;
+  typedef std::unordered_map<T, number_type, hash_fkt> numberst;
   numberst numbers;
 };
 
diff --git a/src/util/old/bitvector.cpp b/src/util/old/bitvector.cpp
deleted file mode 100644
index 1c2fc7086e8..00000000000
--- a/src/util/old/bitvector.cpp
+++ /dev/null
@@ -1,56 +0,0 @@
-/*******************************************************************\
-
-Module:
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#if 0
-#include "string2int.h"
-#include "type.h"
-#include "bitvector.h"
-
-/*******************************************************************\
-
-Function: bv_sem
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-bv_semt bv_sem(const typet &type)
-{
-  if(type.id()==ID_bv)
-    return BV_NONE;
-  else if(type.id()==ID_unsignedbv)
-    return BV_UNSIGNED;
-  else if(type.id()==ID_signedbv)
-    return BV_SIGNED;
-
-  return BV_UNKNOWN;
-}
-
-/*******************************************************************\
-
-Function: bv_width
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-unsigned bv_width(const typet &type)
-{
-  return unsafe_string2unsigned(type.get_string(ID_width));
-}
-
-
-#endif
diff --git a/src/util/old/bitvector.h b/src/util/old/bitvector.h
deleted file mode 100644
index 76451fd8613..00000000000
--- a/src/util/old/bitvector.h
+++ /dev/null
@@ -1,10 +0,0 @@
-// This file is deprecated, and will disappear.
-
-//class typet;
-
-//typedef enum { BV_UNKNOWN, BV_NONE, BV_SIGNED, BV_UNSIGNED } bv_semt;
-
-//bv_semt bv_sem(const typet &type);
-
-// depreciated, and will disappear
-//unsigned bv_width(const typet &type);
diff --git a/src/util/old/cnf_simplify.cpp b/src/util/old/cnf_simplify.cpp
deleted file mode 100644
index a47702e521d..00000000000
--- a/src/util/old/cnf_simplify.cpp
+++ /dev/null
@@ -1,247 +0,0 @@
-/*******************************************************************\
-
-Module:
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#include <cassert>
-
-#include "cnf_simplify.h"
-#include "expr.h"
-
-void cnf_propagate_not(exprt &expr);
-void cnf_join_binary(exprt &expr);
-void propagate_not(exprt &expr);
-
-/*******************************************************************\
-
-Function: cnf_simplify
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-void cnf_simplify(exprt &expr)
-{
-  cnf_propagate_not(expr);
-  cnf_join_binary(expr);
-}
-
-#if 0
-/*******************************************************************\
-
-Function:
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-void cnf_join_binary(exprt &expr)
-{
-  Forall_operands(it, expr)
-    cnf_join_binary(*it);
-
-  if(expr.id()==ID_and || expr.id()==ID_or || expr.id()==ID_xor ||
-     expr.id()==ID_bitand || expr.id()==ID_bitor || expr.id()==ID_bitxor)
-  {
-    exprt tmp;
-
-    if(expr.operands().size()==1)
-    {
-      tmp.swap(expr.op0());
-      expr.swap(tmp);
-    }
-    else
-    {
-      unsigned count=0;
-
-      forall_operands(it, expr)
-      {
-        if(it->id()==expr.id())
-          count+=it->operands().size();
-        else
-          count++;
-      }
-
-      tmp.operands().reserve(count);
-
-      Forall_operands(it, expr)
-      {
-        if(it->id()==expr.id())
-        {
-          Forall_operands(it2, *it)
-            tmp.move_to_operands(*it2);
-        }
-        else
-          tmp.move_to_operands(*it);
-      }
-
-      expr.operands().swap(tmp.operands());
-    }
-  }
-}
-#endif
-
-/*******************************************************************\
-
-Function: cnf_join_binary_collect
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-void cnf_join_binary_collect(exprt &expr, exprt::operandst &list)
-{
-  Forall_operands(it, expr)
-  {
-    if(it->id()==expr.id() && it->type()==expr.type())
-      cnf_join_binary_collect(*it, list);
-    else
-    {
-      list.resize(list.size()+1);
-      list.back().swap(*it);
-    }
-  }
-}
-
-/*******************************************************************\
-
-Function: cnf_join_binary
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-void cnf_join_binary(exprt &expr)
-{
-  if(expr.id()==ID_and || expr.id()==ID_or || expr.id()==ID_xor ||
-     expr.id()==ID_bitand || expr.id()==ID_bitor || expr.id()==ID_bitxor)
-  {
-    exprt::operandst list;
-
-    cnf_join_binary_collect(expr, list);
-
-    if(list.size()==1)
-      expr.swap(list.front());
-    else
-      expr.operands().swap(list);
-  }
-
-  Forall_operands(it, expr)
-    cnf_join_binary(*it);
-}
-
-/*******************************************************************\
-
-Function: cnf_propagate_not
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-void cnf_propagate_not(exprt &expr)
-{
-  if(expr.id()==ID_not)
-  {
-    if(expr.operands().size()==1)
-    {
-      exprt tmp;
-
-      tmp.swap(expr.op0());
-      propagate_not(tmp);
-      expr.swap(tmp);
-    }
-  }
-  else if(expr.id()==ID_nor)
-  {
-    expr.id(ID_or);
-    propagate_not(expr);
-  }
-  else if(expr.id()==ID_nand)
-  {
-    expr.id(ID_and);
-    propagate_not(expr);
-  }
-  else if(expr.id()==ID_implies)
-  {
-    if(expr.operands().size()==2)
-    {
-      expr.id(ID_or);
-      propagate_not(expr.op0());
-    }
-  }
-
-  Forall_operands(it, expr)
-    cnf_propagate_not(*it);
-}
-
-/*******************************************************************\
-
-Function: propagate_not
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-void propagate_not(exprt &expr)
-{
-  if(expr.id()==ID_and || expr.id()==ID_or)
-  {
-    if(expr.id()==ID_and)
-      expr.id(ID_or);
-    else // or
-      expr.id(ID_and);
-
-    Forall_operands(it, expr)
-      propagate_not(*it);
-  }
-  else if(expr.id()==ID_nor)
-    expr.id(ID_or);
-  else if(expr.id()==ID_nand)
-    expr.id(ID_and);
-  else if(expr.id()==ID_not)
-  {
-    assert(expr.operands().size()==1);
-    exprt tmp;
-    tmp.swap(expr.op0());
-    expr.swap(tmp);
-  }
-  else if(expr.id()==ID_equal)
-    expr.id(ID_notequal);
-  else if(expr.id()==ID_notequal)
-    expr.id(ID_equal);
-  else
-  {
-    exprt tmp;
-    expr.swap(tmp);
-    expr.id(ID_not);
-    expr.type()=tmp.type();
-    expr.move_to_operands(tmp);
-  }
-}
diff --git a/src/util/old/cnf_simplify.h b/src/util/old/cnf_simplify.h
deleted file mode 100644
index 01f4ec3473b..00000000000
--- a/src/util/old/cnf_simplify.h
+++ /dev/null
@@ -1,8 +0,0 @@
-#ifndef CPROVER_UTIL_OLD_CNF_SIMPLIFY_H
-#define CPROVER_UTIL_OLD_CNF_SIMPLIFY_H
-
-class exprt;
-
-void cnf_simplify(exprt &expr);
-
-#endif // CPROVER_UTIL_OLD_CNF_SIMPLIFY_H
diff --git a/src/util/old/collection.h b/src/util/old/collection.h
deleted file mode 100644
index 83f7a9e41dd..00000000000
--- a/src/util/old/collection.h
+++ /dev/null
@@ -1,191 +0,0 @@
-/*******************************************************************\
-
-Module: String Storage
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#ifndef CPROVER_UTIL_OLD_COLLECTION_H
-#define CPROVER_UTIL_OLD_COLLECTION_H
-
-#include "string_hash.h"
-#include "hash_cont.h"
-
-template <class T, class hash_function>
-class collection
-{
-public:
-  typedef T valuet;
-
-  typedef hash_map_cont<T, unsigned, hash_function> member_mapt;
-  typedef std::vector<T> member_vectort;
-
-  typedef typename member_mapt::const_iterator const_iterator;
-
-  const_iterator begin() const
-  {
-    return member_map.begin();
-  }
-
-  const_iterator end() const
-  {
-    return member_map.end();
-  }
-
-  class membert
-  {
-  public:
-    membert()
-    {
-    }
-
-    friend bool operator < (const membert &a, const membert &b)
-    {
-      return a.nr<b.nr;
-    }
-
-    membert(unsigned _nr):nr(_nr)
-    {
-    }
-
-    friend class collection;
-
-    unsigned get_nr() const
-    {
-      return nr;
-    }
-
-  protected:
-    unsigned nr;
-  };
-
-  membert member(const T &x)
-  {
-    std::pair<typename member_mapt::iterator, bool> result=
-      member_map.insert(std::pair<T, unsigned>(x, member_vector.size()));
-
-    if(result.second)
-      member_vector.push_back(x);
-
-    return membert(result.first->second);
-  }
-
-  const T &operator [] (const membert m) const
-  {
-    return member_vector[m.nr];
-  }
-
-  const membert operator [] (const T &x)
-  {
-    return member(x);
-  }
-
-  void clear()
-  {
-    member_map.clear();
-    member_vector.clear();
-  }
-
-protected:
-  member_mapt member_map;
-  member_vectort member_vector;
-};
-
-template <class T>
-class collection_set
-{
-public:
-  typedef T collectiont;
-
-  collection_set():collection(NULL)
-  {
-  }
-
-  void insert(unsigned nr)
-  {
-    if(members.size()<nr) members.resize(nr, false);
-    members[nr]=true;
-  }
-
-  bool is_member(unsigned nr) const
-  {
-    if(members.size()<nr) return members[nr];
-    return false;
-  }
-
-  void insert(
-    collectiont &_collection,
-    const typename collectiont::valuet &x)
-  {
-    set_collection(_collection);
-    insert(_collection[x].get_nr());
-  }
-
-  #if 0
-  void insert(
-    collectiont &_collection,
-    const collection_set &x)
-  {
-    set_collection(_collection);
-
-    if(x.collection==NULL) return;
-
-    for(unsigned i=0; i<x.members.size(); i++)
-    {
-
-    }
-  }
-  #endif
-
-  bool is_member(
-    const typename collectiont::valuet &x) const
-  {
-    if(collection==NULL) return false;
-    return is_member((*collection)[x].get_nr());
-  }
-
-  bool empty() const
-  {
-    for(unsigned i=0; i<members.size(); i++)
-      if(members[i]) return false;
-
-    return true;
-  }
-
-  void clear()
-  {
-    collection=NULL;
-    members.clear();
-  }
-
-  void swap(collection_set &x)
-  {
-    std::swap(collection, x.collection);
-    members.swap(x.members);
-  }
-
-  void insert(
-    collection_set &x)
-  {
-
-  }
-
-protected:
-  typedef std::vector<bool> memberst;
-  memberst members;
-
-  void set_collection(collectiont &_collection)
-  {
-    if(collection==NULL)
-      collection=&_collection;
-    else
-      assert(collection==&_collection);
-  }
-
-  collectiont *collection;
-};
-
-typedef collection_set<collection<std::string, string_hash> > string_collection_set;
-
-#endif // CPROVER_UTIL_OLD_COLLECTION_H
diff --git a/src/util/old/oexpr.cpp b/src/util/old/oexpr.cpp
deleted file mode 100644
index e5c76870f38..00000000000
--- a/src/util/old/oexpr.cpp
+++ /dev/null
@@ -1,21 +0,0 @@
-/*******************************************************************\
-
-Module: Expression Representation
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#include "oexpr.h"
-
-/*******************************************************************\
-
-Function:
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
diff --git a/src/util/old/oexpr.h b/src/util/old/oexpr.h
deleted file mode 100644
index b8d89b184f9..00000000000
--- a/src/util/old/oexpr.h
+++ /dev/null
@@ -1,163 +0,0 @@
-/*******************************************************************\
-
-Module:
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#ifndef CPROVER_UTIL_OLD_OEXPR_H
-#define CPROVER_UTIL_OLD_OEXPR_H
-
-#include "expr.h"
-#include "std_types.h"
-
-class oexprt:public exprt
-{
-public:
-  explicit inline oexprt(const exprt &src):exprt(src)
-  {
-  }
-
-  inline oexprt(const irep_idt &_id, const typet &_type):exprt(_id, _type)
-  {
-  }
-
-  inline oexprt(
-    const exprt &a, const irep_idt &_id, const exprt &b,
-    const typet &_type):exprt(_id, _type)
-  {
-    copy_to_operands(a, b);
-  }
-
-  inline oexprt(
-    const irep_idt &_id, const exprt &a,
-    const typet &_type):exprt(_id, _type)
-  {
-    copy_to_operands(a);
-  }
-
-  inline oexprt operator[](const exprt &_index) const
-  {
-    return oexprt(*this, ID_index, _index, type().subtype());
-  }
-};
-
-inline oexprt operator+(const exprt &a, const exprt &b)
-{
-  return oexprt(a, ID_plus, b, a.type());
-}
-
-inline oexprt operator-(const exprt &a, const exprt &b)
-{
-  return oexprt(a, ID_minus, b, a.type());
-}
-
-inline oexprt operator-(const exprt &a)
-{
-  return oexprt(ID_unary_minus, a, a.type());
-}
-
-inline exprt operator*(const exprt &a, const oexprt &b)
-{
-  return oexprt(a, ID_mult, b, a.type());
-}
-
-inline exprt operator*(const exprt &a)
-{
-  return oexprt(ID_dereference, a, a.type().subtype());
-}
-
-inline oexprt operator/(const exprt &a, const exprt &b)
-{
-  return oexprt(a, ID_div, b, a.type());
-}
-
-inline oexprt operator%(const exprt &a, const exprt &b)
-{
-  return oexprt(a, ID_mod, b, a.type());
-}
-
-inline oexprt operator&&(const exprt &a, const exprt &b)
-{
-  return oexprt(a, ID_and, b, bool_typet());
-}
-
-inline oexprt operator||(const exprt &a, const exprt &b)
-{
-  return oexprt(a, ID_or, b, bool_typet());
-}
-
-inline oexprt operator&(const exprt &a, const exprt &b)
-{
-  return oexprt(a, ID_bitand, b, a.type());
-}
-
-inline oexprt operator|(const exprt &a, const exprt &b)
-{
-  return oexprt(a, ID_bitor, b, a.type());
-}
-
-inline oexprt operator~(const exprt &a)
-{
-  return oexprt(ID_bitnot, a, a.type());
-}
-
-inline oexprt operator>>(const exprt &a, const exprt &b)
-{
-  return oexprt(a, ID_shr, b, a.type());
-}
-
-inline oexprt operator<<(const exprt &a, const exprt &b)
-{
-  return oexprt(a, ID_shl, b, a.type());
-}
-
-inline oexprt operator==(const oexprt &a, const oexprt &b)
-{
-  return oexprt(a, ID_equal, b, bool_typet());
-}
-
-inline oexprt operator!=(const oexprt &a, const oexprt &b)
-{
-  return oexprt(a, ID_notequal, b, bool_typet());
-}
-
-inline oexprt operator!(const oexprt &a)
-{
-  return oexprt(ID_not, a, bool_typet());
-}
-
-inline oexprt operator<(const oexprt &a, const oexprt &b)
-{
-  return oexprt(a, ID_lt, b, bool_typet());
-}
-
-inline oexprt operator>(const oexprt &a, const oexprt &b)
-{
-  return oexprt(a, ID_gt, b, bool_typet());
-}
-
-inline oexprt operator<=(const oexprt &a, const oexprt &b)
-{
-  return oexprt(a, ID_le, b, bool_typet());
-}
-
-inline oexprt operator>=(const oexprt &a, const oexprt &b)
-{
-  return oexprt(a, ID_ge, b, bool_typet());
-}
-
-static inline oexprt ite(const oexprt &cond, const oexprt &a, const oexprt &b)
-{
-  oexprt result(ID_if, a.type());
-  result.copy_to_operands(cond, a, b);
-  return result;
-}
-
-static inline oexprt typecast(const oexprt &a, const typet &t)
-{
-  return oexprt(ID_typecast, a, t);
-}
-
-#endif // CPROVER_UTIL_OLD_OEXPR_H
diff --git a/src/util/old/set_stack.h b/src/util/old/set_stack.h
deleted file mode 100644
index 6dcd155c4d3..00000000000
--- a/src/util/old/set_stack.h
+++ /dev/null
@@ -1,149 +0,0 @@
-#ifndef CPROVER_UTIL_OLD_SET_STACK_H
-#define CPROVER_UTIL_OLD_SET_STACK_H
-
-#include <set>
-#include <list>
-
-template <class T>
-class set_stack
-{
- protected:
-  typedef std::multiset<T> sett;
-  typedef typename sett::iterator set_iterator;
-  typedef typename sett::const_iterator set_const_iterator;
-  typedef typename std::list<set_iterator> listt;
-  typedef typename listt::size_type list_size_type;
-
- public:
-  typedef typename sett::const_iterator const_iterator;
-
-  const T &front() const
-  { return *l.front(); }
-
-  const T &back() const
-  { return *l.back(); }
-
-  T &front()
-  { return *l.front(); }
-
-  T &back()
-  { return *l.back(); }
-
-  const_iterator begin() const
-  { return s.begin(); }
-
-  const_iterator end() const
-  { return s.end(); }
-
-  set_const_iterator find(const T &e) const
-  { return s.find(e); }
-
-  void push_back(const T &e)
-  { l.push_back(s.insert(e)); }
-
-  void pop_back()
-  {
-    s.erase(l.back());
-    l.pop_back();
-  }
-
-  list_size_type size() const
-  { return l.size(); }
-
-  const T &back() const
-  { return *l.back(); }
-
-  void resize(list_size_type s);
-
-  bool empty() const
-  { return l.empty(); }
-
- protected:
-  sett s;
-  listt l;
-};
-
-template <class T>
-void set_stack<T>::resize(list_size_type s)
-{
-  if(l.size()>s)
-  {
-    for(unsigned i=l.size()-s; i!=0; i--)
-      pop_back();
-  }
-  else if(l.size()<s)
-  {
-    T e;
-
-    for(unsigned i=s-l.size(); i!=0; i--)
-      push_back(e);
-  }
-}
-
-#include "hash_cont.h"
-
-template <class T, class H>
-class hash_set_stack
-{
- protected:
-  typedef typename hash_multiset_cont<T, H> sett;
-  typedef typename sett::iterator set_iterator;
-  typedef typename sett::const_iterator set_const_iterator;
-  typedef typename std::list<set_iterator> listt;
-  typedef typename listt::size_type list_size_type;
-
- public:
-  typedef set_const_iterator const_iterator;
-
-  const_iterator begin() const
-  { return s.begin(); }
-
-  const_iterator end() const
-  { return s.end(); }
-
-  set_const_iterator find(const T &e) const
-  { return s.find(e); }
-
-  void push_back(const T &e)
-  { l.push_back(s.insert(e)); }
-
-  void pop_back()
-  {
-    s.erase(l.back());
-    l.pop_back();
-  }
-
-  list_size_type size() const
-  { return l.size(); }
-
-  const T &back() const
-  { return *l.back(); }
-
-  void resize(list_size_type s);
-
-  bool empty() const
-  { return l.empty(); }
-
- protected:
-  sett s;
-  listt l;
-};
-
-template <class T, class H>
-void hash_set_stack<T, H>::resize(list_size_type s)
-{
-  if(l.size()>s)
-  {
-    for(unsigned i=l.size()-s; i!=0; i--)
-      pop_back();
-  }
-  else if(l.size()<s)
-  {
-    T e;
-
-    for(unsigned i=s-l.size(); i!=0; i--)
-      push_back(e);
-  }
-}
-
-#endif // CPROVER_UTIL_OLD_SET_STACK_H
diff --git a/src/util/options.cpp b/src/util/options.cpp
index 3d8bdbeb421..e1cb8a369db 100644
--- a/src/util/options.cpp
+++ b/src/util/options.cpp
@@ -6,7 +6,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 \*******************************************************************/
 
-#include "i2string.h"
 #include "string2int.h"
 #include "options.h"
 
@@ -63,7 +62,7 @@ Function: optionst::set_option
 void optionst::set_option(const std::string &option,
                           const signed int value)
 {
-  set_option(option, i2string(value));
+  set_option(option, std::to_string(value));
 }
 
 /*******************************************************************\
@@ -81,7 +80,7 @@ Function: optionst::set_option
 void optionst::set_option(const std::string &option,
                           const unsigned int value)
 {
-  set_option(option, i2string(value));
+  set_option(option, std::to_string(value));
 }
 
 /*******************************************************************\
@@ -99,7 +98,7 @@ Function: optionst::get_bool_option
 bool optionst::get_bool_option(const std::string &option) const
 {
   const std::string value=get_option(option);
-  return value.empty()?false:(safe_string2int(value)!=0);
+  return value.empty()?false:(std::stoi(value)!=0);
 }
 
 /*******************************************************************\
@@ -117,7 +116,7 @@ Function: optionst::get_signed_int_option
 signed int optionst::get_signed_int_option(const std::string &option) const
 {
   const std::string value=get_option(option);
-  return value.empty()?0:safe_string2int(value);
+  return value.empty()?0:std::stoi(value);
 }
 
 /*******************************************************************\
diff --git a/src/util/parser.cpp b/src/util/parser.cpp
index 28ed62d6fbd..6162fca2570 100644
--- a/src/util/parser.cpp
+++ b/src/util/parser.cpp
@@ -7,7 +7,6 @@ Author: Daniel Kroening, kroening@kroening.com
 \*******************************************************************/
 
 #include "parser.h"
-#include "i2string.h"
 
 #ifdef _WIN32
 int isatty(int f)
diff --git a/src/util/pointer_predicates.cpp b/src/util/pointer_predicates.cpp
index 89116356ee8..732781878a2 100644
--- a/src/util/pointer_predicates.cpp
+++ b/src/util/pointer_predicates.cpp
@@ -7,6 +7,7 @@ Author: Daniel Kroening, kroening@kroening.com
 \*******************************************************************/
 
 #include "cprover_prefix.h"
+#include "namespace.h"
 #include "std_expr.h"
 #include "expr_util.h"
 #include "arith_tools.h"
diff --git a/src/util/pointer_predicates.h b/src/util/pointer_predicates.h
index 999c2df030e..a3b88e80cc6 100644
--- a/src/util/pointer_predicates.h
+++ b/src/util/pointer_predicates.h
@@ -9,7 +9,9 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_UTIL_POINTER_PREDICATES_H
 #define CPROVER_UTIL_POINTER_PREDICATES_H
 
-#include "namespace.h"
+class exprt;
+class namespacet;
+class typet;
 
 exprt same_object(const exprt &p1, const exprt &p2);
 exprt deallocated(const exprt &pointer, const namespacet &ns);
diff --git a/src/util/pretty_names.cpp b/src/util/pretty_names.cpp
deleted file mode 100644
index 9c7b822fbea..00000000000
--- a/src/util/pretty_names.cpp
+++ /dev/null
@@ -1,116 +0,0 @@
-/*******************************************************************\
-
-Module: Pretty name generation
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#include "identifier.h"
-#include "pretty_names.h"
-#include "namespace.h"
-#include "symbol.h"
-
-/*******************************************************************\
-
-Function: pretty_namest::get_pretty_names
-
-  Inputs:
-
- Outputs:
-
- Purpose: make displayed variable names unique, but
-          as short as possible
-
-\*******************************************************************/
-
-#if 0
-void pretty_namest::get_pretty_names(
-  const symbolst &symbols,
-  const namespacet &ns)
-{
-  symbolst todo(symbols);
-
-  // first try base names
-  std::multiset<irep_idt> names;
-
-  for(symbolst::const_iterator
-      it=symbols.begin();
-      it!=symbols.end();
-      it++)
-  {
-    const symbolt *symbol;
-    if(ns.lookup(*it, symbol))
-      pretty_map[*it]=*it;
-    else
-    {
-      names.insert(symbol->base_name);
-      pretty_map[*it]=symbol->base_name;
-    }
-  }
-
-  std::map<irep_idt, unsigned> name_components;
-
-  // find collisions
-
-  while(1)
-  {
-    std::set<irep_idt> collisions;
-
-    for(symbolst::const_iterator it=symbols.begin();
-        it!=symbols.end(); it++)
-      if(names.count(pretty_map[*it])>=2)
-        collisions.insert(*it);
-
-    if(collisions.empty())
-      return; // done
-
-    names.clear();
-
-    for(std::set<irep_idt>::const_iterator it=collisions.begin();
-        it!=collisions.end(); it++)
-    {
-      unsigned no_components=(++name_components[*it]);
-
-      identifiert id(id2string(*it));
-
-      if(no_components>=id.components.size())
-        pretty_map[*it]=*it;
-      else
-      {
-        while(no_components<id.components.size())
-          id.components.erase(
-            id.components.begin(),
-            id.components.begin()+(id.components.size()-no_components));
-
-        std::string new_name=id.as_string();
-
-        names.insert(new_name);
-        pretty_map[*it]=new_name;
-      }
-    }
-  }
-}
-#endif
-
-/*******************************************************************\
-
-Function: pretty_namest::pretty_names
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-#if 0
-const irep_idt &pretty_namest::pretty_name(
-  const irep_idt &identifier) const
-{
-  pretty_mapt::const_iterator it=pretty_map.find(identifier);
-  if(it==pretty_map.end()) return identifier;
-  return it->second;
-}
-#endif
diff --git a/src/util/pretty_names.h b/src/util/pretty_names.h
deleted file mode 100644
index f1776c16c1e..00000000000
--- a/src/util/pretty_names.h
+++ /dev/null
@@ -1,37 +0,0 @@
-/*******************************************************************\
-
-Module: Pretty name generation
-
-Author: Daniel Kroening, kroening@kroening.com
-
-\*******************************************************************/
-
-#ifndef CPROVER_UTIL_PRETTY_NAMES_H
-#define CPROVER_UTIL_PRETTY_NAMES_H
-
-// THIS FILE WILL GO AWAY
-
-#include <set>
-#include <map>
-
-#include "irep.h"
-
-class namespacet;
-
-#if 0
-class pretty_namest
-{
- public:
-  typedef std::set<irep_idt> symbolst;
-  typedef std::map<irep_idt, irep_idt> pretty_mapt;
-
-  pretty_mapt pretty_map;
-
-  void get_pretty_names(const symbolst &symbols,
-                        const namespacet &ns);
-
-  const irep_idt &pretty_name(const irep_idt &identifier) const;
-};
-#endif
-
-#endif // CPROVER_UTIL_PRETTY_NAMES_H
diff --git a/src/util/rational_tools.cpp b/src/util/rational_tools.cpp
index 08f303c31f9..22b5263a485 100644
--- a/src/util/rational_tools.cpp
+++ b/src/util/rational_tools.cpp
@@ -6,8 +6,9 @@ Author: Daniel Kroening, kroening@kroening.com
 
 \*******************************************************************/
 
-#include "std_expr.h"
+#include "rational.h"
 #include "std_types.h"
+
 #include "rational_tools.h"
 
 /*******************************************************************\
diff --git a/src/util/rational_tools.h b/src/util/rational_tools.h
index fecadc17f1a..34dcf8d4932 100644
--- a/src/util/rational_tools.h
+++ b/src/util/rational_tools.h
@@ -9,7 +9,9 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_UTIL_RATIONAL_TOOLS_H
 #define CPROVER_UTIL_RATIONAL_TOOLS_H
 
-#include "rational.h"
+#include "std_expr.h"
+
+class rationalt;
 
 bool to_rational(const exprt &expr, rationalt &rational_value);
 constant_exprt from_rational(const rationalt &rational_value);
diff --git a/src/util/ref_expr_set.h b/src/util/ref_expr_set.h
index a607d15baeb..197351399ce 100644
--- a/src/util/ref_expr_set.h
+++ b/src/util/ref_expr_set.h
@@ -9,18 +9,17 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_UTIL_REF_EXPR_SET_H
 #define CPROVER_UTIL_REF_EXPR_SET_H
 
-#include <set>
+#include <unordered_set>
 
-#include "hash_cont.h"
 #include "expr.h"
 #include "reference_counting.h"
 
-extern const hash_set_cont<exprt, irep_hash> empty_expr_set;
+extern const std::unordered_set<exprt, irep_hash> empty_expr_set;
 
 struct ref_expr_set_dt
 {
   ref_expr_set_dt() {}
-  typedef hash_set_cont<exprt, irep_hash> expr_sett;
+  typedef std::unordered_set<exprt, irep_hash> expr_sett;
   expr_sett expr_set;
 
   const static ref_expr_set_dt blank;
diff --git a/src/util/rename.cpp b/src/util/rename.cpp
index 3b66de68257..b121edb6acb 100644
--- a/src/util/rename.cpp
+++ b/src/util/rename.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <algorithm>
 
 #include "rename.h"
-#include "i2string.h"
 #include "symbol.h"
 #include "expr.h"
 #include "namespace.h"
@@ -51,7 +50,7 @@ void get_new_name(irep_idt &new_name, const namespacet &ns)
 
   std::string prefix=id2string(new_name)+"_";
 
-  new_name=prefix+i2string(ns.get_max(prefix)+1);
+  new_name=prefix+std::to_string(ns.get_max(prefix)+1);
 }
 
 /*******************************************************************\
diff --git a/src/util/rename_symbol.h b/src/util/rename_symbol.h
index 0beb85516f8..1e75c92e169 100644
--- a/src/util/rename_symbol.h
+++ b/src/util/rename_symbol.h
@@ -14,14 +14,18 @@ Author: Daniel Kroening, kroening@kroening.com
 // false: renamed something
 //
 
-#include "hash_cont.h"
-#include "expr.h"
+#include <unordered_map>
+
+#include "irep.h"
+
+class exprt;
+class typet;
 
 class rename_symbolt
 {
 public:
-  typedef hash_map_cont<irep_idt, irep_idt, irep_id_hash> expr_mapt;
-  typedef hash_map_cont<irep_idt, irep_idt, irep_id_hash> type_mapt;
+  typedef std::unordered_map<irep_idt, irep_idt, irep_id_hash> expr_mapt;
+  typedef std::unordered_map<irep_idt, irep_idt, irep_id_hash> type_mapt;
 
   inline void insert_expr(const irep_idt &old_id,
                           const irep_idt &new_id)
diff --git a/src/util/replace_expr.h b/src/util/replace_expr.h
index 9a804b1d785..74b2a64374c 100644
--- a/src/util/replace_expr.h
+++ b/src/util/replace_expr.h
@@ -14,10 +14,9 @@ Author: Daniel Kroening, kroening@kroening.com
 // false: replaced something
 //
 
-#include "hash_cont.h"
 #include "expr.h"
 
-typedef hash_map_cont<exprt, exprt, irep_hash> replace_mapt;
+typedef std::unordered_map<exprt, exprt, irep_hash> replace_mapt;
 
 bool replace_expr(const exprt &what, const exprt &by, exprt &dest);
 bool replace_expr(const replace_mapt &what, exprt &dest);
diff --git a/src/util/replace_symbol.h b/src/util/replace_symbol.h
index b27cd1f0378..8fad66c80ba 100644
--- a/src/util/replace_symbol.h
+++ b/src/util/replace_symbol.h
@@ -14,14 +14,13 @@ Author: Daniel Kroening, kroening@kroening.com
 // false: replaced something
 //
 
-#include "hash_cont.h"
 #include "expr.h"
 
 class replace_symbolt
 {
 public:
-  typedef hash_map_cont<irep_idt, exprt, irep_id_hash> expr_mapt;
-  typedef hash_map_cont<irep_idt, typet, irep_id_hash> type_mapt;
+  typedef std::unordered_map<irep_idt, exprt, irep_id_hash> expr_mapt;
+  typedef std::unordered_map<irep_idt, typet, irep_id_hash> type_mapt;
 
   inline void insert(const irep_idt &identifier,
                      const exprt &expr)
diff --git a/src/util/simplify_expr.cpp b/src/util/simplify_expr.cpp
index 865a3e982e0..2894544b8db 100644
--- a/src/util/simplify_expr.cpp
+++ b/src/util/simplify_expr.cpp
@@ -9,6 +9,7 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <cassert>
 #include <algorithm>
 
+#include "rational.h"
 #include "simplify_expr_class.h"
 #include "simplify_expr.h"
 #include "mp_arith.h"
@@ -47,10 +48,10 @@ struct simplify_expr_cachet
   friend class simplify_exprt;
 
   #if 1
-  typedef hash_map_cont<
+  typedef std::unordered_map<
     exprt, exprt, irep_full_hash, irep_full_eq> containert;
   #else
-  typedef hash_map_cont<
+  typedef std::unordered_map<
     exprt, exprt, irep_hash> containert;
   #endif
 
diff --git a/src/util/simplify_expr_boolean.cpp b/src/util/simplify_expr_boolean.cpp
index aa98a85b13b..89df15cf7be 100644
--- a/src/util/simplify_expr_boolean.cpp
+++ b/src/util/simplify_expr_boolean.cpp
@@ -7,6 +7,7 @@ Author: Daniel Kroening, kroening@kroening.com
 \*******************************************************************/
 
 #include <cassert>
+#include <unordered_set>
 
 #include "simplify_expr_class.h"
 #include "expr.h"
@@ -146,7 +147,7 @@ bool simplify_exprt::simplify_boolean(exprt &expr)
     {
       // first gather all the a's with !a
 
-      hash_set_cont<exprt, irep_hash> expr_set;
+      std::unordered_set<exprt, irep_hash> expr_set;
 
       forall_operands(it, expr)
         if(it->id()==ID_not &&
diff --git a/src/util/simplify_expr_class.h b/src/util/simplify_expr_class.h
index eeaa7e2bcfe..cfaea165f36 100644
--- a/src/util/simplify_expr_class.h
+++ b/src/util/simplify_expr_class.h
@@ -14,7 +14,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <sys/stat.h>
 #endif
 
-#include <map>
 #include <set>
 
 #include "type.h"
diff --git a/src/util/simplify_expr_int.cpp b/src/util/simplify_expr_int.cpp
index 98dab123a3f..acc1c0453a7 100644
--- a/src/util/simplify_expr_int.cpp
+++ b/src/util/simplify_expr_int.cpp
@@ -8,10 +8,11 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <cassert>
 
+#include "base_type.h"
+#include "rational.h"
 #include "simplify_expr_class.h"
 #include "expr.h"
 #include "namespace.h"
-#include "namespace_utils.h"
 #include "config.h"
 #include "bv_arithmetic.h"
 #include "std_expr.h"
@@ -478,7 +479,7 @@ bool simplify_exprt::simplify_plus(exprt &expr)
 
     // search for a and -a
     // first gather all the a's with -a
-    typedef hash_map_cont<exprt, exprt::operandst::iterator, irep_hash>
+    typedef std::unordered_map<exprt, exprt::operandst::iterator, irep_hash>
       expr_mapt;
     expr_mapt expr_map;
 
diff --git a/src/util/std_expr.cpp b/src/util/std_expr.cpp
index 25e18ceb09d..5efc4d6e70c 100644
--- a/src/util/std_expr.cpp
+++ b/src/util/std_expr.cpp
@@ -13,7 +13,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include "config.h"
 #include "namespace.h"
 #include "pointer_offset_size.h"
-#include "i2string.h"
 
 #include "std_types.h"
 #include "std_expr.h"
@@ -200,7 +199,7 @@ Function: constant_exprt::integer_constant
 
 constant_exprt constant_exprt::integer_constant(unsigned v)
 {
-  return constant_exprt(i2string(v), integer_typet());
+  return constant_exprt(std::to_string(v), integer_typet());
 }
 
 /*******************************************************************\
diff --git a/src/util/string2int.cpp b/src/util/string2int.cpp
index c5112c41d9b..7e746610118 100644
--- a/src/util/string2int.cpp
+++ b/src/util/string2int.cpp
@@ -15,7 +15,7 @@ Author: Michael Tautschnig, michael.tautschnig@cs.ox.ac.uk
 
 /*******************************************************************\
 
-Function: safe_c_str2number
+Function: str2number
 
   Inputs:
 
@@ -62,57 +62,6 @@ inline T str2number(const char *str, int base, bool safe)
 
 /*******************************************************************\
 
-Function: safe_c_str2int
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-int safe_c_str2int(const char *str, int base)
-{
-  return str2number<int>(str, base, true);
-}
-
-/*******************************************************************\
-
-Function: safe_c_str2unsigned
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-unsigned safe_c_str2unsigned(const char *str, int base)
-{
-  return str2number<unsigned>(str, base, true);
-}
-
-/*******************************************************************\
-
-Function: safe_string2int
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-int safe_string2int(const std::string &str, int base)
-{
-  return str2number<int>(str.c_str(), base, true);
-}
-
-/*******************************************************************\
-
 Function: safe_string2unsigned
 
   Inputs:
@@ -147,40 +96,6 @@ std::size_t safe_string2size_t(const std::string &str, int base)
 
 /*******************************************************************\
 
-Function: unsafe_c_str2int
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-int unsafe_c_str2int(const char *str, int base)
-{
-  return str2number<int>(str, base, false);
-}
-
-/*******************************************************************\
-
-Function: unsafe_c_str2unsigned
-
-  Inputs:
-
- Outputs:
-
- Purpose:
-
-\*******************************************************************/
-
-unsigned unsafe_c_str2unsigned(const char *str, int base)
-{
-  return str2number<unsigned>(str, base, false);
-}
-
-/*******************************************************************\
-
 Function: unsafe_string2int
 
   Inputs:
diff --git a/src/util/string2int.h b/src/util/string2int.h
index f77aed0274e..1a660eba864 100644
--- a/src/util/string2int.h
+++ b/src/util/string2int.h
@@ -13,21 +13,13 @@ Author: Michael Tautschnig, michael.tautschnig@cs.ox.ac.uk
 
 // These check that the string is indeed a valid number,
 // and fail an assertion otherwise.
-int safe_c_str2int(const char *str, int base=10);
-unsigned safe_c_str2unsigned(const char *str, int base=10);
-
-int safe_string2int(const std::string &str, int base=10);
+// We use those for data types that C++11's std::stoi etc. do not
+// cover.
 unsigned safe_string2unsigned(const std::string &str, int base=10);
 std::size_t safe_string2size_t(const std::string &str, int base=10);
 
-// The safe_* functions will eventually go away, and will be replaced
-// by C++11 std::stoi, std::stol, std::stoll, std::stoul and so on.
-
 // The below mimick C's atoi/atol: any errors are silently ignored.
 // They are meant to replace atoi/atol.
-int unsafe_c_str2int(const char *str, int base=10);
-unsigned unsafe_c_str2unsigned(const char *str, int base=10);
-
 int unsafe_string2int(const std::string &str, int base=10);
 unsigned unsafe_string2unsigned(const std::string &str, int base=10);
 std::size_t unsafe_string2size_t(const std::string &str, int base=10);
diff --git a/src/util/string_container.h b/src/util/string_container.h
index e4dda7d393d..c2ce0b22939 100644
--- a/src/util/string_container.h
+++ b/src/util/string_container.h
@@ -10,9 +10,9 @@ Author: Daniel Kroening, kroening@kroening.com
 #define CPROVER_UTIL_STRING_CONTAINER_H
 
 #include <list>
+#include <unordered_map>
 #include <vector>
 
-#include "hash_cont.h"
 #include "string_hash.h"
 
 struct string_ptrt
@@ -73,7 +73,7 @@ class string_containert
 
 protected:
   // the 'unsigned' ought to be size_t
-  typedef hash_map_cont<string_ptrt, unsigned, string_ptr_hash> hash_tablet;
+  typedef std::unordered_map<string_ptrt, unsigned, string_ptr_hash> hash_tablet;
   hash_tablet hash_table;
 
   unsigned get(const char *s);
diff --git a/src/util/symbol.h b/src/util/symbol.h
index f10084184f4..3f821421719 100644
--- a/src/util/symbol.h
+++ b/src/util/symbol.h
@@ -113,24 +113,6 @@ class symbolt
 std::ostream &operator<<(std::ostream &out,
                          const symbolt &symbol);
 
-#include <list>
-
-typedef std::list<symbolt> symbol_listt;
-
-#define forall_symbol_list(it, expr) \
-  for(symbol_listt::const_iterator it=(expr).begin(); \
-      it!=(expr).end(); ++it)
-
-typedef std::list<const symbolt *> symbolptr_listt;
-
-#define forall_symbolptr_list(it, list) \
-  for(symbolptr_listt::const_iterator it=(list).begin(); \
-      it!=(list).end(); ++it)
-
-#define Forall_symbolptr_list(it, list) \
-  for(symbolptr_listt::iterator it=(list).begin(); \
-      it!=(list).end(); ++it)
-
 /*! \brief Symbol table entry describing a data type
     \ingroup gr_symbol_table
 
diff --git a/src/util/symbol_table.h b/src/util/symbol_table.h
index b9905f215b8..b0fc5b7840b 100644
--- a/src/util/symbol_table.h
+++ b/src/util/symbol_table.h
@@ -20,8 +20,8 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <iosfwd>
 #include <map>
+#include <unordered_map>
 
-#include "hash_cont.h"
 #include "symbol.h"
 
 #define forall_symbols(it, expr) \
@@ -51,7 +51,7 @@ typedef std::multimap<irep_idt, irep_idt> symbol_module_mapt;
 class symbol_tablet
 {
 public:
-  typedef hash_map_cont<irep_idt, symbolt, irep_id_hash> symbolst;
+  typedef std::unordered_map<irep_idt, symbolt, irep_id_hash> symbolst;
 
   symbolst symbols;
   symbol_base_mapt symbol_base_map;
diff --git a/src/util/tempfile.cpp b/src/util/tempfile.cpp
index 3a6dd24e7cd..143b702abf6 100644
--- a/src/util/tempfile.cpp
+++ b/src/util/tempfile.cpp
@@ -32,7 +32,6 @@ Author: Daniel Kroening
 #include <fcntl.h>
 #endif
 
-#include "i2string.h"
 #include "tempfile.h"
 
 /*******************************************************************\
@@ -122,7 +121,7 @@ std::string get_temporary_file(
   // the path returned by GetTempPath ends with a backslash
   std::string t_template=
     std::string(lpTempPathBuffer)+prefix+
-    i2string(getpid())+".XXXXXX"+suffix;
+    std::to_string(getpid())+".XXXXXX"+suffix;
   #else
   std::string dir="/tmp/";
   const char *TMPDIR_env=getenv("TMPDIR");
@@ -131,7 +130,7 @@ std::string get_temporary_file(
   if(*dir.rbegin()!='/') dir+='/';
 
   std::string t_template=
-    dir+prefix+i2string(getpid())+".XXXXXX"+suffix;
+    dir+prefix+std::to_string(getpid())+".XXXXXX"+suffix;
   #endif
 
   char *t_ptr=strdup(t_template.c_str());
diff --git a/src/util/type.h b/src/util/type.h
index 6e007d261ff..1fa20503f80 100644
--- a/src/util/type.h
+++ b/src/util/type.h
@@ -9,8 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_UTIL_TYPE_H
 #define CPROVER_UTIL_TYPE_H
 
-#include <list>
-
 #include <util/source_location.h>
 
 #define SUBTYPE_IN_GETSUB
@@ -148,16 +146,6 @@ class type_with_subtypest:public typet
   #endif
 };
 
-typedef std::list<typet> type_listt;
-
-#define forall_type_list(it, type) \
-  for(type_listt::const_iterator it=(type).begin(); \
-      it!=(type).end(); ++it)
-
-#define Forall_type_list(it, type) \
-  for(type_listt::iterator it=(type).begin(); \
-      it!=(type).end(); ++it)
-
 #define forall_subtypes(it, type) \
   if((type).has_subtypes()) \
     for(typet::subtypest::const_iterator it=(type).subtypes().begin(), \
diff --git a/src/util/ui_message.cpp b/src/util/ui_message.cpp
index afa79a8d75c..4296c14666f 100644
--- a/src/util/ui_message.cpp
+++ b/src/util/ui_message.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <fstream>
 #include <iostream>
 
-#include "i2string.h"
 #include "xml.h"
 #include "json.h"
 #include "xml_expr.h"
@@ -212,7 +211,7 @@ void ui_message_handlert::print(
       const char *type=level_string(level);
 
       std::string sequence_number_str=
-        sequence_number>=0?i2string(sequence_number):"";
+        sequence_number>=0?std::to_string(sequence_number):"";
 
       ui_msg(type, tmp_message, sequence_number_str, location);
     }
diff --git a/src/util/xml.cpp b/src/util/xml.cpp
index fd8a870ec8d..957424302f3 100644
--- a/src/util/xml.cpp
+++ b/src/util/xml.cpp
@@ -9,7 +9,6 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <ostream>
 
 #include "string2int.h"
-#include "i2string.h"
 #include "xml.h"
 
 /*******************************************************************\
@@ -148,7 +147,7 @@ void xmlt::escape(const std::string &s, std::ostream &out)
     default:
       // &#0; isn't allowed, but what shall we do?
       if((ch>=0 && ch<' ') || ch==127)
-        out << "&#"+i2string((unsigned char)ch)+";";
+        out << "&#"+std::to_string((unsigned char)ch)+";";
       else
         out << ch;
     }
@@ -194,7 +193,7 @@ void xmlt::escape_attribute(const std::string &s, std::ostream &out)
     default:
       // &#0; isn't allowed, but what shall we do?
       if((ch>=0 && ch<' ') || ch==127)
-        out << "&#"+i2string((unsigned char)ch)+";";
+        out << "&#"+std::to_string((unsigned char)ch)+";";
       else
         out << ch;
     }
@@ -281,7 +280,7 @@ void xmlt::set_attribute(
   const std::string &attribute,
   unsigned value)
 {
-  set_attribute(attribute, i2string(value));
+  set_attribute(attribute, std::to_string(value));
 }
 
 /*******************************************************************\
@@ -300,7 +299,7 @@ void xmlt::set_attribute(
   const std::string &attribute,
   unsigned long value)
 {
-  set_attribute(attribute, i2string(value));
+  set_attribute(attribute, std::to_string(value));
 }
 
 /*******************************************************************\
@@ -319,7 +318,7 @@ void xmlt::set_attribute(
   const std::string &attribute,
   unsigned long long value)
 {
-  set_attribute(attribute, i2string(value));
+  set_attribute(attribute, std::to_string(value));
 }
 
 /*******************************************************************\
diff --git a/src/xmllang/graphml.cpp b/src/xmllang/graphml.cpp
index 1a8530f7ae0..c1ab6760f4f 100644
--- a/src/xmllang/graphml.cpp
+++ b/src/xmllang/graphml.cpp
@@ -11,7 +11,6 @@ Author: Michael Tautschnig, mt@eecs.qmul.ac.uk
 
 #include <util/message.h>
 #include <util/string2int.h>
-#include <util/i2string.h>
 
 #include "graphml.h"
 
@@ -586,7 +585,7 @@ bool write_graphml(const graphmlt &src, std::ostream &os)
     {
       xmlt &entry=node.new_element("data");
       entry.set_attribute("key", "threadNumber");
-      entry.data=i2string(n.thread_nr);
+      entry.data=std::to_string(n.thread_nr);
     }
 
     // <node id="A14">