Chapter-4/4-4/polishcalc.c
/* swap:  swap the two top elements of the stack */
swap the two top elements of the stack
swap the two top elements of the stack
void swap_top(void) {
  double tmp1 = pop();
  double tmp2 = pop();
  push(tmp1);
  push(tmp2);
}
void swap_top ( void ) { double tmp1 = pop ( ) ; double tmp2 = pop ( ) ; push ( tmp1 ) ; push ( tmp2 ) ; }
swap:  swap the two top elements of the stack
swap : swap the two top elements of the stack