Flex i Bison/Kalkulator z prostymi zmiennymi - parser

%{
    #include <stdlib.h>
    #include <stdio.h>
    int yylex(void);
    void yyerror(char* );
    double var[26];
%}

%union { double dval; int ivar; }
%token <dval> DOUBLE
%token <ivar> NAME
%type <dval> expr
%type <dval> mulex
%type <dval> term

%%
program
: line program
| line
;

line
: expr '\n' { printf("%g\n",$1); }
| NAME '=' expr '\n' { var[$1] = $3; }
;

expr
: expr '+' mulex { $$ = $1 + $3; }
| expr '-' mulex { $$ = $1 - $3; }
| mulex { $$ = $1; }
;

mulex 
: mulex '*' term { $$ = $1 * $3; }
| mulex '/' term { $$ = $1 / $3; }
| term { $$ = $1; }
;

term
: '(' expr ')' { $$ = $2; }
| NAME { $$ = var[$1]; }
| DOUBLE { $$ = $1; }
;

%%

void yyerror(char *s)
{
    fprintf(stderr,"%s\n",s);
    return;
}

int main(void)
{
    /*yydebug=1;*/
    yyparse();
    return 0;
}