#include <stdio.h>
#include <stdlib.h>    /* atof() */

#define MAXLEN 100

/* function prototypes */
int getop(char []);
void push(double);
double pop(void);

/* reverse Polish calculator */
main()
{
  int type;
  double op2;
  char s[MAXLEN];

  while ((type = getop(s)) != EOF) {
    switch (type) {
    case '0':
      push(atof(s));
      break;
    case '+':
      push(pop() + pop());
      break;
    case '*':
      push(pop() * pop());
      break;
    case '-':
      op2 = pop();
      push(pop() - op2);
      break;
    case '/':
      op2 = pop();
      if (op2 != 0.0)
        push(pop() / op2);
      else
        printf("ERROR: Division by zero!\n");
      break;
    case '\n':
      printf("\t%f\n", pop());
      break;
    default:
      printf("ERROR: Unknown input!\n");
      break;
    }
  }
}