Function Pointers

Ek function, ek variable ki tarah, ek address par rehta hai — aur C aapko wo address ek pointer mein store karne deta hai. int (*operation)(int, int) operation ko do ints lene wale aur ek int return karne wale function ke pointer ke roop mein declare karta hai; use ek function naam assign karna (call kiye bina) us function ka address store kar deta hai.

#include <stdio.h>

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

int main() {
    int (*operation)(int, int) = add;
    printf("%d\n", operation(5, 3));
    operation = subtract;
    printf("%d\n", operation(5, 3));
    return 0;
}

8
2

operation(5, 3) call karna jo bhi function operation currently point kar raha hai use call karta hai — pehli baar add, reassignment ke baad subtract. Isi tarah C callbacks aur dynamic dispatch implement karta hai, bina is site ki doosri languages ke class ya interface machinery ke jo isi idea ke liye use hoti hai.

Aage: preprocessor — ek alag, purely textual pass jo compiler ke aapka code dekhne se pehle run hota hai.