Struct function & function pointer

#include<stdio.h>
#include<stdlib.h>
//  Structure function 
struct str_func{
    int a;
    int b;
    int (*add)(int a,int b);// A function pointer , It's essentially a pointer variable , Point to the function address ,
    int(*sub) (int a, int b);
    int (*compare)(int a, int b);
};

//  A function pointer 


int add(int a,int b){
    return a+b ;
}

int sub(int a,int b){
    return a-b;
}

int compare(int a, int b){
    if (a>b){
        return a;
    }
    else 
        return b;
}

struct str_func test = {
    .a=5,
    .b=7,
    .add=add,
    .sub = sub,
    .compare = compare,
};
int main(){
    if (test.compare){
        printf("a b max=%d\n",(test.compare(test.a,test.b)));
    };
    if (test.compare){
        printf("a add b =%d\n",(test.add(test.a,test.b)));
    };
    if (test.compare){
        printf("a b max=%d\n",(test.sub(test.a,test.b)));
    };
    
}