Function Pointers

A function pointer stores the address of a function so code can call one operation through a variable.

function_pointers.c

#include <stdio.h>

int doubleValue(int value) {
    return value * 2;
}

int tripleValue(int value) {
    return value * 3;
}

int apply(int value, int (*op)(int)) {
    return op(value);
}

int main(void) {
    int value = ;
    int useTriple = ;
    int result = 0;

    if (useTriple) {
        result = apply(value, tripleValue);
    } else {
        result = apply(value, doubleValue);
    }

    printf("result=%d\n", result);
    return 0;
}

#include <stdio.h>

int doubleValue(int value) {
    return value * 2;
}

int tripleValue(int value) {
    return value * 3;
}

int apply(int value, int (*op)(int)) {
    return op(value);
}

int main(void) {
    int value = ;
    int useTriple = ;
    int result = 0;

    if (useTriple) {
        result = apply(value, tripleValue);
    } else {
        result = apply(value, doubleValue);
    }

    printf("result=%d\n", result);
    return 0;
}

#include <stdio.h>

int doubleValue(int value) {
    return value * 2;
}

int tripleValue(int value) {
    return value * 3;
}

int apply(int value, int (*op)(int)) {
    return op(value);
}

int main(void) {
    int value = ;
    int useTriple = ;
    int result = 0;

    if (useTriple) {
        result = apply(value, tripleValue);
    } else {
        result = apply(value, doubleValue);
    }

    printf("result=%d\n", result);
    return 0;
}

#include <stdio.h>

int doubleValue(int value) {
    return value * 2;
}

int tripleValue(int value) {
    return value * 3;
}

int apply(int value, int (*op)(int)) {
    return op(value);
}

int main(void) {
    int value = ;
    int useTriple = ;
    int result = 0;

    if (useTriple) {
        result = apply(value, tripleValue);
    } else {
        result = apply(value, doubleValue);
    }

    printf("result=%d\n", result);
    return 0;
}

#include <stdio.h>

int doubleValue(int value) {
    return value * 2;
}

int tripleValue(int value) {
    return value * 3;
}

int apply(int value, int (*op)(int)) {
    return op(value);
}

int main(void) {
    int value = ;
    int useTriple = ;
    int result = 0;

    if (useTriple) {
        result = apply(value, tripleValue);
    } else {
        result = apply(value, doubleValue);
    }

    printf("result=%d\n", result);
    return 0;
}

#include <stdio.h>

int doubleValue(int value) {
    return value * 2;
}

int tripleValue(int value) {
    return value * 3;
}

int apply(int value, int (*op)(int)) {
    return op(value);
}

int main(void) {
    int value = ;
    int useTriple = ;
    int result = 0;

    if (useTriple) {
        result = apply(value, tripleValue);
    } else {
        result = apply(value, doubleValue);
    }

    printf("result=%d\n", result);
    return 0;
}

function pointer `int (*op)(int)` is a pointer to a function that takes and returns an `int`.

callback Passing a function pointer lets another function call back into the selected operation.