Pass function as argument Dry Run in C

Pass function as argument is an interactive C dry run visualizer from the Pointersfunctions programs section. Study the source code, then use the execution controls to follow each step, variable update, highlighted line, and console output.

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Pass function as argument Program Code

#include <stdio.h>

// Different transformation functions
int square(int x) { return x * x; }
int cube(int x) { return x * x * x; }
int timesTwo(int x) { return x * 2; }
int plusTen(int x) { return x + 10; }

// Generic function that applies transformation to array
void applyToArray(int *arr, int size, int (*transform)(int)) {
    int i;
    for(i = 0; i < size; i++) {
        arr[i] = transform(arr[i]);
    }
}

// Function that returns function pointer based on choice
int (*selectOperation(int choice))(int) {
    int (*ops[4])(int) = {square, cube, timesTwo, plusTen};
    if(choice >= 0 && choice < 4) {
        return ops[choice];
    }
    return square;  // default
}

// Higher-order function: apply operation and print
void processAndPrint(int *arr, int size, int (*op)(int), char *opName) {
    int i;
    printf("\nApplying %s:\n", opName);
    printf("Before: ");
    for(i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    
    applyToArray(arr, size, op);
    
    printf("\nAfter:  ");
    for(i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}

int main() {
    int i;
    int numbers[] = {1, 2, 3, 4, 5};
    int size = 5;
    int temp[5];
    int (*op)(int);
    
    // Pass different functions to applyToArray
    printf("=== Passing functions as arguments ===\n");
    
    // Square
    for(i = 0; i < size; i++) {
        temp[i] = numbers[i];
    }
    processAndPrint(temp, size, square, "square");
    
    // Cube
    for(i = 0; i < size; i++) {
        temp[i] = numbers[i];
    }
    processAndPrint(temp, size, cube, "cube");
    
    // Times two
    for(i = 0; i < size; i++) {
        temp[i] = numbers[i];
    }
    processAndPrint(temp, size, timesTwo, "timesTwo");
    
    // Return function pointer from function
    printf("\n=== Returning function pointers ===\n");
    op = selectOperation(1);  // Get cube function
    printf("cube(5) = %d\n", op(5));
    
    return 0;
}

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