Add new join_strings function that applies a function to the elements of the container it flattens

and add tests for it.

Author: NlightNFotis

src/util/string_utils.h

@@ -50,19 +50,34 @@ std::string trim_from_last_delimiter(
 /// \return A reference to the ostream that was passed in
 template<typename Stream, typename It, typename Delimiter>
 Stream &join_strings(
-  Stream &os,
+  Stream &&os,
   const It b,
   const It e,
   const Delimiter &delimiter)
+{
+  using value_type = decltype(*b);
+  // Call auxiliary function with identity function
+  return join_strings(os, b, e, delimiter, [](const value_type &x) {
+    return x;
+  });
+}
+
+template<typename Stream, typename It, typename Delimiter, typename ToStringFunc>
+Stream &join_strings(
+  Stream &&os,
+  const It b,
+  const It e,
+  const Delimiter &delimiter,
+  ToStringFunc &&to_string_func)
 {
   if(b==e)
   {
     return os;
   }
-  os << *b;
+  os << to_string_func(*b);
   for(auto it=std::next(b); it!=e; ++it)
   {
-    os << delimiter << *it;
+    os << delimiter << to_string_func(*it);
   }
   return os;
 }

unit/Makefile

@@ -69,6 +69,7 @@ SRC += analyses/ai/ai.cpp \
 			 util/std_expr.cpp \
        util/string_utils/split_string.cpp \
        util/string_utils/strip_string.cpp \
+       util/string_utils/join_string.cpp \
        util/symbol_table.cpp \
        util/symbol.cpp \
        util/unicode.cpp \

unit/util/string_utils/join_string.cpp

@@ -0,0 +1,33 @@
+/*******************************************************************\
+
+Module: Unit tests of join_string
+
+Author: Diffblue Ltd.
+
+\*******************************************************************/
+
+/// \file
+/// join_string Unit Tests
+
+#include <vector>
+#include <sstream>
+#include <string>
+
+#include <testing-utils/use_catch.h>
+#include <util/string_utils.h>
+
+TEST_CASE("join_strings() should apply the function argument its passed to the elements of the container")
+{
+  std::vector<int> vec{1, 2, 3};
+  auto result = join_strings(std::ostringstream(), vec.begin(), vec.end(), "-", [](int x){
+      return std::to_string(x);
+  }).str();
+  REQUIRE(result == "1-2-3");
+}
+
+TEST_CASE("join_strings() when passed no function argument should apply the default identity function to the elements of the container")
+{
+  std::vector<int> vec{1, 2, 3};
+  auto result = join_strings(std::ostringstream(), vec.begin(), vec.end(), ",").str();
+  REQUIRE(result == "1,2,3");
+}