#include <stdlib.h>
#include <stdio.h>
#include "stack4.h"

class RPN : public Stack {
   int getop(int* n1, int* n2);
 public:
   void sum() { int n1, n2; if (getop(&n1, &n2)) push(n1+n2); }
   void sub() { int n1, n2; if (getop(&n1, &n2)) push(n1-n2); }
   void mul() { int n1, n2; if (getop(&n1, &n2)) push(n1*n2); }
   void div() { int n1, n2; if (getop(&n1, &n2)) push(n1/n2); }
};

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

int main(void)
{
   RPN* s = new RPN;
   while (1)
   {
      char str[31];
      int n;
      printf("> ");
      gets(str);
      if (sscanf(str, " %d", &n)==1) s->push(n);
      else
      {
         char c;
         sscanf(str, "%c", &c);
         switch(c)
         {
            case '+': s->sum(); break;
            case '-': s->sub(); break;
            case '*': s->mul(); break;
            case '/': s->div(); break;
            case 'q': delete s; return 0;
            default:
               printf("error\n");
         }
      }

      int i = 0;
      StackIterator si(s);
      while (!si.end())
         printf("%d:%6d\n", i++, si.next());
   }
}