Function Pointers in C

1#include <stdio.h>
2
3// A simple function
4int add(int a, int b) {
5    return a + b;
6}
7
8int subtract(int a, int b) {
9    return a - b;
10}
11
12int main() {
13    // Declare a function pointer
14    // It can point to any function that:
15    // - Returns int
16    // - Takes two int parameters
17    int (*operation)(int, int);
18    
19    // Point to 'add' function
20    operation = add;  // or: operation = &add;
21    
22    // Call through pointer
23    int result = operation(10, 5);
24    printf("add(10, 5) = %d\n", result);
25    
26    // Point to 'subtract' function
27    operation = subtract;
28    
29    result = operation(10, 5);
30    printf("subtract(10, 5) = %d\n", result);
31    
32    return 0;
33}

1#include <stdio.h>
2
3// Callback function type for processing array elements
4void applyToArray(int* arr, int size, int (*callback)(int)) {
5    for (int i = 0; i < size; i++) {
6        arr[i] = callback(arr[i]);  // Apply callback to each element
7    }
8}
9
10// Functions to use as callbacks
11int doubleValue(int x) {
12    return x * 2;
13}
14
15int square(int x) {
16    return x * x;
17}
18
19int addTen(int x) {
20    return x + 10;
21}
22
23void printArray(int* arr, int size) {
24    for (int i = 0; i < size; i++) {
25        printf("%d ", arr[i]);
26    }
27    printf("\n");
28}
29
30int main() {
31    int numbers[] = {1, 2, 3, 4, 5};
32    int size = 5;
33    
34    printf("Original: ");
35    printArray(numbers, size);
36    
37    // Apply 'double' callback
38    applyToArray(numbers, size, doubleValue);
39    printf("Doubled:  ");
40    printArray(numbers, size);
41    
42    // Reset and apply 'square'
43    int nums2[] = {1, 2, 3, 4, 5};
44    applyToArray(nums2, size, square);
45    printf("Squared:  ");
46    printArray(nums2, size);
47    
48    // Reset and apply 'addTen'
49    int nums3[] = {1, 2, 3, 4, 5};
50    applyToArray(nums3, size, addTen);
51    printf("Add 10:   ");
52    printArray(nums3, size);
53    
54    return 0;
55}

1#include <stdio.h>
2
3int add(int a, int b) { return a + b; }
4int subtract(int a, int b) { return a - b; }
5int multiply(int a, int b) { return a * b; }
6int divide(int a, int b) { return b != 0 ? a / b : 0; }
7
8int main() {
9    // Array of function pointers
10    int (*operations[4])(int, int) = {add, subtract, multiply, divide};
11    char* names[] = {"Add", "Subtract", "Multiply", "Divide"};
12    
13    int a = 20, b = 5;
14    
15    printf("Calculator Demo (a=%d, b=%d):\n\n", a, b);
16    
17    for (int i = 0; i < 4; i++) {
18        int result = operations[i](a, b);  // Call through array
19        printf("%s: %d\n", names[i], result);
20    }
21    
22    // Menu-driven selection
23    printf("\nEnter operation (0=Add, 1=Sub, 2=Mul, 3=Div): ");
24    int choice = 0;  // Simulating user input
25    printf("%d\n", choice);
26    
27    printf("Result: %d\n", operations[choice](a, b));
28    
29    return 0;
30}

1#include <stdio.h>
2
3// Define a type for our function pointer
4typedef int (*Operation)(int, int);
5
6int add(int a, int b) { return a + b; }
7int multiply(int a, int b) { return a * b; }
8
9// Now function parameters are clean!
10int calculate(int a, int b, Operation op) {
11    return op(a, b);
12}
13
14int main() {
15    // Clean variable declaration
16    Operation myOp = add;
17    printf("add: %d\n", myOp(10, 5));
18    
19    myOp = multiply;
20    printf("multiply: %d\n", myOp(10, 5));
21    
22    // Pass to function easily
23    printf("calculate with add: %d\n", calculate(10, 5, add));
24    printf("calculate with multiply: %d\n", calculate(10, 5, multiply));
25    
26    return 0;
27}