问Bison Stack赋值

EN

#include <iostream> 
#include <cstdio>

#define YY_DECL extern "C" int yylex()

#include "conv.tab.h"
using namespace std;

%}
eq [ \t]*=
%%

[ \t]           ;
(?:POINT|LINE)  { yylval.ename = strdup(yytext); return ENAME; }
x{eq}           { yylval.xval = atof(yytext);
                    return XVAL; }
y{eq}           { yylval.yval = atof(yytext);
                    return YVAL; }
.               ;
%%

%{
#include <iostream>
#include <cstdio>
#include <stdio.h>
using namespace std;

extern "C" int yylex ();
extern "C" int yyparse (void);
extern "C" FILE *yyin;
extern int line_no;

void yyerror(const char *s);

%}

%union{
    float xval;
    float yval;
    char *ename;
}

%token <ename> ENAME
%token XVAL
%token YVAL

%%

converter:
    converter ENAME { cout << "entity = " << $2 << endl; }
    | converter XVAL {// x -> xval = $2; 
      cout << "x value = " << endl; }
    | converter YVAL {// y -> yval = $2; 
       cout << "y value = " << endl; }
    | ENAME { cout << "entity = " << $1 << endl; }
    | XVAL { cout << "xvalue " << endl; }
    | YVAL { cout << "yvalue " << endl; }

%%
main() {
    FILE *myfile = fopen("conv.aj", "r");

    if (!myfile) {
            cout << "I can't open file" << endl;
            return -1;
    }

    yyin = myfile;

    do{
            yydebug = 1;
            yyparse();
    } while (!feof(yyin));
    yydebug = 2;
}

void yyerror(const char *s) {
    cout << "Parser error! Message: " << s << endl;
    exit(-1);
}