#include <stdlib.h>
#include <stdio.h>
#include "stack-c.h"

int getop(struct Stack* s, int* n1, int* n2)
{
   if (empty(s))
   {
      printf("empty stack!\n");
      return 0;
   }
   *n2 = pop(s);
   if (empty(s))
   {
      push(s, *n2);
      printf("two operands needed!\n");
      return 0;
   }
   *n1 = pop(s);
   return 1;
}

int main(void)
{
   struct Stack* s = createStack();
   while (1)
   {
      char str[31];
      int i;
      printf("> ");
      gets(str);
      if (sscanf(str, " %d", &i)==1) push(s, i);
      else
      {
         int n1, n2;
         char c;
         sscanf(str, "%c", &c);
         switch(c)
         {
            case '+':
               if (getop(s, &n1, &n2)) push(s, n1+n2);
               break;
            case '-':
               if (getop(s, &n1, &n2)) push(s, n1-n2);
               break;
            case '/':
               if (getop(s, &n1, &n2)) push(s, n1/n2);
               break;
            case '*':
               if (getop(s, &n1, &n2)) push(s, n1*n2);
               break;
            case 'q':
               return 0;
            default:
               printf("error\n");
         }
      }
      {
         int i;
         for (i=0; i<s->top; i++)
            printf("%d:%6d\n", i, s->elems[i]);
      }
   }
}