Flex i Bison/Kalkulator z dynamicznymi zmiennymi - parser

%{
    #include <stdlib.h>
    #include <stdio.h>
    #include <string.h>
    int yylex(void);
    void yyerror(char* );
    #define NVARS 100
    char *vars[NVARS]; double vals[NVARS]; int nvars=0;
%}

%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' { vals[$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 ')'       { $$ = $2; }
| NAME               { $$ = vals[$1]; }
| DOUBLE             { $$ = $1; }
;

%%

int varindex(char *var)
{
    int i;
    for (i = 0; i < nvars; i++)
    if (strcmp(var, vars[i]) == 0) return i;
    vars[nvars] = strdup(var);
    return nvars++;
}

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

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