/*
Postfix calculator

file: main.c++
author: Jakob Klepp
date: 2017-03-09
*/

#include <iostream>
#include "stack.h++"

typedef enum e_inputType {
  BINARY_OPERATION,
  EVALUATE,
  NUMBER,
} InputType;

typedef struct t_input {
  InputType inputType;
  int value;
} Input;

Input getInput();
int operateBinary(char op, int n1, int n2);

int main(int argc, char const *argv[]) {
  Stack stack = Stack_new();
  Input in;
  int n1, n2, res;
  bool evaluated = false;

  do {
    in = getInput();
    switch (in.inputType) {
      case BINARY_OPERATION:
        n2 = Stack_pop(&stack);
        n1 = Stack_pop(&stack);
        res = operateBinary(in.value, n1, n2);
        Stack_push(&stack, res);
        break;
      case EVALUATE:
        std::cout << Stack_pop(&stack) << '\n';
        evaluated = true;
        break;
      case NUMBER:
        Stack_push(&stack, in.value);
        break;
    }
  } while (!Stack_isEmpty(&stack) && !evaluated);

  Stack_destroy(&stack);

  return 0;
}

Input getInput() {
  char in;
  int number;

  while (true) {
    std::cin.get(in);
    if ('+' == in || '-' == in ||
        '*' == in || '/' == in ||
        '%' == in) {
      return (Input){ BINARY_OPERATION, in };
    } else if ('=' == in) {
      return (Input){ EVALUATE, '=' };
    } else if ('0' <= in && '9' >= in) {
      number = in - '0';
      for (int i = 1; i <= 10; i++) {
        std::cin.get(in);
        if ('0' <= in && '9' >= in) {
          number = number * 10 + in - '0';
        } else {
          break;
        }
      }
      return (Input){ NUMBER, number };
    }
  }
}

int operateBinary(char op, int n1, int n2) {
  switch (op) {
    case '+': return n1 + n2;
    case '-': return n1 - n2;
    case '*': return n1 * n2;
    case '/': return n1 / n2;
    case '%': return n1 % n2;
  }
}