#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>
#define print_int_expr_and_value(n)            printf("%6s == %d\n", (#n), (n))
#define print_address_expr_and_value(address)  printf("%6s == %p\n", (#address), (void*)(address))
// swap_wrong_2(…) - WRONG -- detect with assert(…) 

void swap_wrong_2(int** a_a_lhs, int** a_a_rhs) {
    int* a_lhs = *a_a_lhs;   // a_a_lhs is an int**  so  *a_a_lhs will be an int*
    int* a_rhs = *a_a_rhs;   // 
    *a_a_lhs = a_rhs;
    *a_a_rhs = a_lhs;
}

int main(int argc, char* argv[]) {
    int n1 =   3;
    int n2 = 100;
    printf("BEFORE:\n");
    print_int_expr_and_value(n1);
    print_int_expr_and_value(n2);

    int* a_n1 = &n1;
    int* a_n2 = &n2;
    assert(a_n1 == &n1);  // should be obvious
    assert(*a_n1 == n1);  // should be obvious
    print_address_expr_and_value(&n1);
    print_address_expr_and_value(&n2);
    print_address_expr_and_value(a_n1);
    print_address_expr_and_value(a_n2);

    swap_wrong_2(&a_n1, &a_n2);
    assert(a_n1 == &n1);  // "I promise that a_n1 == &n1 (or else you can blame me for bugs)."
    assert(*a_n1 == n1);  // "I promise that *a_n1 == n1 (or else you can blame me for bugs)."

    // Thanks to the assert(…), we learn that our variable names a_n1 and a_n2 were DECEPTIVE.
    // Because our swap(…) was buggy, a_n1 is actually the adddress of n2 (and likewise for a_n2 and n1)
    // Deceptive variable names are EVIL.
    printf("\nCalled swap(&a_n1, &a_n2)\n\n");

    printf("AFTER:\n");
    print_int_expr_and_value(n1);
    print_int_expr_and_value(n2);
    print_address_expr_and_value(&n1);
    print_address_expr_and_value(&n2);
    print_address_expr_and_value(a_n1);
    print_address_expr_and_value(a_n2);
    print_int_expr_and_value(*a_n1);
    print_int_expr_and_value(*a_n2);

    // DECEPTIVE:  a_n1 seems to mean "address of n1" but it now contains &n2 (address of n2)
    return EXIT_SUCCESS;
}
/* vim: set tabstop=4 shiftwidth=4 fileencoding=utf-8 noexpandtab: */