Why generated parser issues syntax error?

Question

I am trying to write a simple grammar which accepts statements of the form

     7 = var int
     9 = abc float

But with the following LEX and YACC code, the generated parser issues syntax error (Calls yyerror)

LEX :---

[0-9]+      { yylval.num = atof(yytext); return NUM; }
"int"       return INT;
"float"     return FLOAT;
[a-z]+      {  yylval.str = strdup(yytext); return ID; }
\n              /* Ignore end of lines */
[ \t]+          /* Ignore white spaces and tabs */

YACC:---

%% 
commands: /* empty */
    | commands command
    ;                                                                                     

command:                                                                                  
    int_exp
    |                                                                                     
    float_exp
    ;                                                                                     

int_exp: exp INT                                                                        
    ;                                          

float_exp: exp FLOAT
    ;

exp : NUM '=' ID
    ;

%%

Answer 1

You need to define a token for '=' in your lex file and use its terminal symbol name instead of '=' in your grammar definition.

[0-9]+      { yylval.num = atof(yytext); return NUM; }
"int"       return INT;
"float"     return FLOAT;
[a-z]+      {  yylval.str = strdup(yytext); return ID; }
\n              /* Ignore end of lines */
[ \t]+          /* Ignore white spaces and tabs */
"="         return ASSIGN;

exp : NUM ASSIGN ID
    ;