फ़ंक्शन पॉइंटर

#include <iostream>

void greet() { std::cout << "Hello\n"; }

int main() {
    void (*g)() = greet;
    g();
    (*g)();
    return 0;
}

#include <iostream>

int apply(int x, int (*fn)(int)) { return fn(x); }
int doubler(int n) { return n * 2; }

int main() {
    std::cout << apply(10, doubler) << '\n';
    return 0;
}

#include <iostream>

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

int main() {
    bool wantAdd = true;
    int (*op)(int, int) = wantAdd ? add : sub;
    std::cout << op(8, 3) << '\n';
    return 0;
}

#include <iostream>

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

int main() {
    int (*ops[2])(int, int) = {add, mul};
    std::cout << ops[0](2, 3) << ' ' << ops[1](2, 3) << '\n';
    return 0;
}

#include <iostream>

using BinOp = int(*)(int, int);
int add(int a, int b) { return a + b; }

int main() {
    BinOp op = add;
    std::cout << op(6, 7) << '\n';
    return 0;
}

#include <iostream>
#include <vector>
#include <algorithm>

bool isEven(int n) { return n % 2 == 0; }

int main() {
    std::vector<int> v = {1, 2, 3, 4, 5, 6};
    int c = std::count_if(v.begin(), v.end(), isEven);
    std::cout << "Evens: " << c << '\n';
    return 0;
}

#include <iostream>

int counter = 0;
int next() { return ++counter; }

int main() {
    int (*fn)() = next;
    std::cout << fn() << ' ' << fn() << ' ' << fn() << '\n';
    return 0;
}

#include <iostream>

int main() {
    int (*fn)(int) = [](int x) { return x + 100; };
    std::cout << fn(1) << '\n';
    return 0;
}

#include <iostream>

int main() {
    int (*fn)(int) = nullptr;
    if (fn) {
        std::cout << fn(5) << '\n';
    } else {
        std::cout << "No function set\n";
    }
    return 0;
}