/*******************************************
  Engineering 4892 Data Structures
  Assignment: 1  Date Due: May 19th/2001
  Name: Daryl Martin
  Student #: 9713520
  Username: darylm
********************************************/

#include "evaluate.h"
#include <iostream>
#include <stack>
#include <cctype>


int evaluate(const std::string& exp) {

	stack<int> numbers;
	stack<char> oper;
	int i = 0;

	while(exp[i]){
		switch(exp[i]){
		
		case '1':
		case '2':
		case '3':
		case '4':
		case '5':
		case '6':
		case '7':
		case '8':
		case '9':
		case '0':
			string buffer;
			buffer = exp[i];
			numbers.push(atoi(buffer.c_str()))
			break;
		case '/':
		case '*':
		case '-':
		case '+':
			oper.push(exp[i]);
			break;
		
		case ')':
			int a = 0;
			int	b = 0;
			char oper;
			a = numbers.top();
			numbers.pop();
			b = numbers.top();
			numbers.pop();
			oper = oper.top();
			oper.pop();
				switch(oper){
					case '/':
					numbers.push(b/a);
					break;
					case '*':
					numbers.push(a*b);
					break;
					case '-':
					numbers.push(b-a);
					break;
					case '+':
					numbers.push(a+b);
					break;
				}
			break;
		}
	i++;
	}
}