#include <stdio.h>

// we define a macro to swap two variables:
//   one should protect all the macro parameters with (...)
//   and the whole macro with {...}
#define   SWAP(A,B)   { temp__yzVBZq = (A); (A) = (B); (B) = temp__yzVBZq; }

// global variable used by the above macro:
int temp__yzVBZq;
// Why do we use this crazy name?

int main(void) {

  // our two variables:
  int one = 1, two = 2;

  // now, we do not want to swap them:
  if (1) SWAP(one,two);

  // look at the result:
  printf("one = %d, two = %d\n", one, two);
  
  // end:
  return 0;
}