/*
 * This is a simple post-fix expression evaluator.  (I needed to exercise the
 * our latest stack, and got tired of completely meaningless stack 
 * manipulation.)  Input is integers, operators +, -, *, /, or the period
 * character as an end marker.  This is evaluated as a postfix expression 
 * with minimal error checking.
 */

#include <iostream>
#include <cctype>
#include <string>

#include "lnkstack.h"

using namespace std;

int main()
{
	// Stack of integers.
	Stack<int> is;

	// Read the input.
	char op;
	while(cin >> op) {
		// See what we got.
		if(op == '.') {
			// Halt char.
			break;
		} else if(isdigit(op)) {
			// Digit.  Unget it, read the number, and push it
			// on the stack.
			cin.unget();
			int val;
			cin >> val;
			is.push(val);
			continue;
		} else if(string("+-*/").find(op) != string::npos) {
			// Operator, pop the operands.
			int a,b;
			if(!is.pop(b)) break;
			if(!is.pop(a)) break;

			// Push the operation result in place of the operands.
			switch(op)
				{
				case '+':
					is.push(a+b);
					break;
				case '-':
					is.push(a-b);
					break;
				case '*':
					is.push(a*b);
					break;
				case '/':
					is.push(a/b);
					break;
				}
		} else {
			// Just what it says.
			cout << "Bad char " << op << endl;
		}
	}

	// If there's a result, print it.  If the stack is empty, just
	// whine about it.
	int res;
	if(is.pop(res))
		cout << "Value: " << res << endl;

	cout << "Stack has " << is.size() << " elements at exit." << endl;
}