flex 'yyval' undeclared

Question

So, I'm very new to flex/bison but I need to write this parser to recognize a simple integer calculator and I was having trouble getting flex and bison to talk to each other.

Flex returns token values like it should and all, but I can't quite get it to actually return semantic values. This is my flex file:

            %option noyywrap
            %{
                #include "test_Calc_Answer.tab.h"
                #include <malloc.h>
                #include <process.h>
                #define fileno _fileno
            %}
            NUM    [0-9]
            %%
            "{"[\^{}}]*"}"

            [ \t]+

            [\n]        {
                            return (int)'\n';
                        }

            "+"         {
                            return (int)'+';
                        }

            "-"         {
                            return (int)'-';
                        }

            "*"         {
                            return (int)'*';
                        }

            "/"         {
                            return (int)'/';
                        }

            {NUM}+      {
                            int i, value = 0;

                            for(i = yyleng-1; i>=0; i--)
                                value = 10*value + ( yytext[i] - '0' );
                            yyval = value;

                            return DIGIT;
                        }
            %%

When I try compiling the generated code, I get a 'yyval undeclared' error. I noticed it is declared in the *.tab.h file so I can't understand what the problem could be. Tell me if I need to provide additional information...

Thanks, sorry for my noobness or if I re-asked a question.

Answer 1

The variable for the lexical value is usually called yylval and not yyval, so that is almost certainly what the variable in your *.tab.h is called.