/*
 * Author: Amit Dutta (amitdutta4255@gmail.com) | Date: 12 Dec 2025
 * Repo: https://github.com/notamitgamer/bsc
 * License: MIT
 */

/* Write a program to swap two numbers using a macro (#define). */

// IMPOSSIBLE
/* It is impossible to swap two literal numbers defined using the 
preprocessor directive #define. This is because #define performs simple 
text substitution and does not create variables in memory that can be 
manipulated or pointed to. */

// Using a Function-Like Macro

#include <stdio.h>

// Define the SWAP macro.
// The do-while(0) block is a common trick to ensure the macro behaves
// like a single statement, regardless of where it is used (e.g., inside an 'if' statement).
#define SWAP(a, b, data_type)   \
    do {                        \
        data_type temp = a;     \
        a = b;                  \
        b = temp;               \
    } while(0)

int main() {
    int num1 = 15;
    int num2 = 42;

    printf("--- Before Swap ---\n");
    printf("Number 1 (num1): %d\n", num1);
    printf("Number 2 (num2): %d\n", num2);

    // Call the macro, passing the variables and their type
    // The preprocessor replaces this line with the block of code defined above.
    SWAP(num1, num2, int);

    printf("\n--- After Swap (using macro) ---\n");
    printf("Number 1 (num1): %d\n", num1);
    printf("Number 2 (num2): %d\n", num2);

    return 0;
}