flex,bison に詳しい方、お願いします。

Question

###前提・実現したいこと
(変数の追加)
例えば、変数A,B,C,Dに、さらに"X", "Y"を加えるようにするためにはどう書けばいいのでしょうか？教えていただければ幸いです。
###理想結果

A=3*4-4;
XX=A*A;
YY=XX+A;
print XX;
64
print YY;
72

###実際の結果

A=3*4-4;
XX=A*A;
YY=XX+A;
print XX;
print YY;

xx

###flex

%%
"\n" {;} /* 改行を無視  */
" " {;}  /* スペースを無視  */
"\t" {;} /* タブを無視  */

print return(PRT);
"=" return(EQU); 
"+" return(ADD); 
"-" return(SUB); 
"*" return(MUL); 
"/" return(DIV); 
"(" return(LPA); 
")" return(RPA); 
";" return(SEM); 
"A" { yylval.val=0.0;
 return (ID);}
"B" { yylval.val=1.0;
 return (ID);}
"C" { yylval.val=2.0;
 return (ID);}
"D" { yylval.val=3.0;
 return (ID);}
"X"{yylval.val=4.0;
return(ID);}
"Y"{yylval.val=4.0;
return(ID);}

[0-9]+ {yylval.val=atof(yytext);
 return (NUM);}
%%
int yywrap(){ /* 定義要 */ return 1;}

###bison

%{
#include <stdio.h>
  double Symtbl[6];
%}
%union{
  double val;
}
%token <val> NUM  ID
%type <val> Expr
%token LPA RPA EQU PRT SEM
%left ADD SUB
%left DIV MUL
%start Program
%%
Program: Statement
       | Program Statement
;
Statement: Assign 
         | Print
;
Assign: ID EQU Expr SEM
{
  Symtbl[(int)($1)]=$3;
}
;
Print: PRT ID SEM
{
  printf("%f\n", Symtbl[(int)($2)]);
}
;
Expr: Expr ADD Expr {$$=$1+$3;}
| Expr SUB Expr {$$=$1-$3;}
| Expr MUL Expr {$$=$1*$3;}
| Expr DIV Expr {$$=$1/$3;}
| LPA Expr RPA {$$=$2;}
| NUM {$$=$1;}
| ID {$$=Symtbl[(int)($1)];}
;
%%
int main(){
  yyparse();
}
int yyerror(char *s)
{ /* 定義要 */
}

###補足情報(言語/FW/ツール等のバージョンなど)
より詳細な情報

Answer 1

This reminds me of my younger days when learning yacc and lex! It may not reach you...

Your codes were almost done but there should be mistyping or copying incorrectly. It might be:

"Y"{yylval.val=5.0; // not 4.0
 return (ID);}

And you have shown a sample input, but it was wrong for your calculator. Something like (not two Xs and Ys but single X and Y to use):

A=3*4-4;
X=A*A;
Y=X+A;
print X;
64.000000
print Y;
72.000000

Modifying only a little bit code and correct inputing do fix this problem.