Function Pointers

Ek function, ek variable ki tarah, ek address par rehta hai — aur C aap ko 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 taur par declare karta hai; use ek function naam assign karna (call kiye baghair) 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;
}

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2

operation(5, 3) call karna jo bhi function operation is waqt 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 istemal hoti hai.

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