/*
This program simulates the behavior of stack4.c.
*/

#include <stdio.h>

int stack[50];
int *stackpointer = stack + 50;
double returnvalue;

int main(void)
{
  /* printf("20 factorial is %f\n",factorial(20)); */
  stackpointer -= 1;
  stackpointer[0] = 271;
  stackpointer -= 1;
  stackpointer[0] = 20;
  goto factorial;
  instruction271:
  printf("20 factorial is %f\n",returnvalue);
  /* return 0; */
  return 0;


  factorial:
#define n (stackpointer[0])

  /* printf("n is %d; &n is %u\n",n,(unsigned int) &n); */
  printf("n is %d; &n is %u\n",n,(unsigned int) &n);

  /* if (!n) return 1; */
  if (!n) {
    returnvalue = 1;
    stackpointer += 2;
    goto returnaddress;
  }

  /* return n * factorial(n - 1); */
  stackpointer -= 1;
  stackpointer[0] = 314;
  stackpointer -= 1;
  stackpointer[0] = stackpointer[2] - 1;
  goto factorial;
  instruction314:
  returnvalue = n * returnvalue;
  stackpointer += 2;
  goto returnaddress;


  returnaddress:
  switch(stackpointer[-1]) {
    case 271: goto instruction271;
    case 314: goto instruction314;
  }
}