smt2 tokenizer: keywords

Keywords are simple symbols preceded by a colon, and used for a range of
purposes in the SMT-LIB2 syntax. The tokenizer now recognizes keywords.

Author: Daniel Kroening

src/solvers/smt2/smt2_tokenizer.cpp

@@ -254,7 +254,13 @@ void smt2_tokenizert::get_token_from_stream()
 
     case ':': // keyword
       token = get_simple_symbol();
-      return;
+      if(token == SYMBOL)
+      {
+        token = KEYWORD;
+        return;
+      }
+      else
+        throw error("expecting symbol after colon");
 
     case '#':
       if(in->get(ch))

src/solvers/smt2/smt2_tokenizer.h

@@ -60,6 +60,7 @@ class smt2_tokenizert:public parsert
     STRING_LITERAL,
     NUMERAL,
     SYMBOL,
+    KEYWORD,
     OPEN,
     CLOSE
   };