bison i need to access the expr

Question

I can use this very nicely but in the expr i want to validate the expr tADD etc i created, but i can not access the expr inside operation, how do i access it ? it just returns the result that is 0

%{
#include <stdio.h>
void yyerror (const char *s)
#define YYSTYPE char *
extern YYSTYPE yylval;
extern int line; 
{}
%}

%token tADD tSUB tMUL tDIV tSTRING tNUM tPRINT tGET tSET tFUNCTION tRETURN tIDENT tEQUALITY tIF tGT tLT tGEQ tLEQ tINC tDEC

%start prog


%%
prog:       '[' stmtlst ']' 
;

stmtlst:    stmtlst stmt |
;

stmt:       setStmt | if | print | unaryOperation | expr | returnStmt
;

getExpr:    '[' tGET ',' tIDENT ',' '[' exprList ']' ']'
        | '[' tGET ',' tIDENT ',' '[' ']' ']'
        | '[' tGET ',' tIDENT ']'
;

setStmt:    '[' tSET ',' tIDENT ',' expr ']'
;

if:     '[' tIF ',' condition ',' '[' stmtlst ']' ']'
        | '[' tIF ',' condition ',' '[' stmtlst ']' '[' stmtlst ']' ']'
;

print:      '[' tPRINT ',' '[' expr ']' ']'
;

operation:  '[' tADD ',' expr ',' expr ']' {
                    if($2){
                        printf("op\n");
                    }
                    printf("%d here ", $4);
            }
        | '[' tSUB ',' expr ',' expr ']'
        | '[' tMUL ',' expr ',' expr ']'
        | '[' tDIV ',' expr ',' expr ']'
;   

unaryOperation: '[' tINC ',' tIDENT ']'
        | '[' tDEC ',' tIDENT ']'
;

expr:        tNUM | tSTRING | function | operation | condition
            
;

function:    '[' tFUNCTION ',' '[' parametersList ']' ',' '[' stmtlst ']' ']'
        | '[' tFUNCTION ',' '[' ']' ',' '[' stmtlst ']' ']'
;

condition:  '[' tEQUALITY ',' expr ',' expr ']'
        | '[' tGT ',' expr ',' expr ']'
        | '[' tLT ',' expr ',' expr ']'
        | '[' tGEQ ',' expr ',' expr ']'
        | '[' tLEQ ',' expr ',' expr ']'
;

returnStmt: '[' tRETURN ',' expr ']'
        | '[' tRETURN ']'
;

parametersList: parametersList ',' tIDENT | tIDENT
;

exprList:   exprList ',' expr | expr{
                printf("%s\n", $1);
        }
;

%%
int main ()
{
if (yyparse()) {
// parse error
printf("ERROR\n");
return 1;
}
else {
// successful parsing
printf("OK\n");
return 0;
}
}

I use $4 but I always get 0 as the value for all Operations,

expr:        tNUM | tSTRING | function | operation | condition
            
;

Also flex that i use

%{
#include "username-hw3.tab.h" 
%}
%%

['][^']*[']     return tSTRING;

["]Get["]       return tGET;
["]Set["]       return tSET;
["]Function["]      return tFUNCTION;
["]Print["]     return tPRINT;
["]If["]        return tIF;
["]Return["]        return tRETURN;

["]"+"["]               return tADD;
["]"-"["]               return tSUB;
["]"*"["]               return tMUL;
["]"/"["]               return tDIV;
["]"++"["]      return tINC;
["]">"["]       return tGT;
["]"=="["]      return tEQUALITY;
["]"--"["]      return tDEC;
["]"<"["]       return tLT;
["]"<="["]      return tLEQ;
["]">="["]      return tGEQ;


["][_a-zA-Z][a-zA-Z0-9_]*["]    return tIDENT;
                
[0-9]+ |
-[0-9]+ |       
[0-9]+"."[0-9]+ |
-[0-9]+"."[0-9]+    return tNUM; 
    
[ \t\n]+ 
.           return yytext[0];

%%