Re: How to get the actual string for a symbol?

[Philip Herron]

On 31/12/2009 05:11, Peng Yu wrote:
> I want to get words from a file and print them out. But I'm not sure
> how to make yylval a pointer to the string yytext. Could somebody let
> me know how to modify the following code so that the string can be
> retrieved the symbol WORD.
>
>    
> > yylval_string.l
> >      
> %option nodefault
> %{
> # include "yylval_string.tab.h"
> %}
> %%
> [A-Za-z]+ { /*I'm not sure how to make yylval a point to yytext */
> return WORD; }
> [[:space:]] { /*SPACE*/ }
> .       {
>   return UNEXPECTED_CHARACTER;
>   /*fprintf(stderr, "unexpeced_character: '%s'\n", yytext);*/
>   }
> %%
>    
> > yylval_string.y
> >      
> %{
> #  include<stdio.h>
> %}
> %token WORD UNEXPECTED_CHARACTER
> %%
> words:
>         WORD { printf("WORD = %s\n", $1); }
>         | words WORD { printf("WORD = %d\n", $2); }
>   ;
> %%
> main()
> {
>    yyparse();
> }
>
> yyerror(char *s)
> {
>    fprintf(stderr, "error: %s\n", s);
> }
>
>
> _______________________________________________
> address@hidden http://lists.gnu.org/mailman/listinfo/help-bison
>    
I am fairly sure this stuff is well documented now, just going to post 
an example from one of my projects...

Lexer:

ID       [_a-zA-Z][a-zA_Z0-9_]*

{ID}                    {
                          yylval.string= xstrdup( yytext );
                          return IDENTIFIER;
                        }

Parser:

union {
  char *string;
  ....
}

%token <string>IDENTIFIER // now points to whatever :)

You might want to think about the difference between keywords and static 
data a little more too. And terminals or non-terminals how it all fits.

--Phil