C++ Function Pointer Tutorial

A function pointer in C++ is a variable that stores the address of a function. Function pointers allow you to call functions dynamically, pass functions as arguments, and implement callback mechanisms.

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1. Basic Function Pointer Example

#include <iostream>
using namespace std;

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

int main() {
    int (*funcPtr)(int, int) = add;
    cout << funcPtr(3, 4) << endl; // Output: 7
    return 0;
}

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2. Why Use Function Pointers?

• Callbacks: Pass functions as arguments to other functions.
• Dynamic Function Calls: Choose which function to call at runtime.
• Implementing Tables of Functions: Useful in menu-driven programs or interpreters.

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3. Passing Function Pointers to Functions

#include <iostream>
using namespace std;

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

void compute(int x, int y, int (*op)(int, int)) {
    cout << op(x, y) << endl;
}

int main() {
    compute(2, 3, add);      // Output: 5
    compute(2, 3, multiply); // Output: 6
    return 0;
}

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4. Array of Function Pointers

#include <iostream>
using namespace std;

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

int main() {
    int (*ops[2])(int, int) = {add, sub};
    cout << ops[0](5, 2) << endl; // Output: 7
    cout << ops[1](5, 2) << endl; // Output: 3
    return 0;
}

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5. Function Pointer Syntax

• Declaration: return_type (*pointer_name)(parameter_types)
• Example: int (*funcPtr)(int, int);

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6. Function Pointers vs Functors vs Lambdas

• Function Pointer: Points to a free/static function.
• Functor: Object with operator(); can hold state.
• Lambda: Anonymous function object; can capture variables.

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Summary

• Function pointers store addresses of functions.
• Useful for callbacks and dynamic function calls.
• Syntax can be tricky but powerful for flexible code.
• For more complex scenarios, consider functors or lambdas.