package CS_240_Project_1;
import java.util.*;

public class RPN implements REPL  {
	ArrayStack<Integer> stack;

	public RPN(){
	    stack = new ArrayStack<Integer>();
	    }

	public String[] read() {
        Scanner sc = new Scanner(System.in);
        System.out.print("rpn> ");
        String ans = sc.next();
        StringTokenizer s = new StringTokenizer(ans);

        int x = 0;
        String[] a = new String[30];
        while (s.hasMoreElements()) {
        	a[x] = s.nextToken();
        	x++;
        }
        return a;
	}

	public void eval(String expr) throws StackUnderflowException {
		if (isInt(expr)) {
			int x = Integer.parseInt(expr);
			stack.push(x);
		}
		else if (expr == "+") {
			int x = stack.pop();
			int y = stack.pop();
			stack.push(x+y);
		}
		else if (expr == "*") {
			int x = stack.pop();
			int y = stack.pop();
			stack.push(x*y);
		}
		else if (expr == "-") {
			int x = stack.pop();
			int y = stack.pop();
			stack.push(y-x);
		}
		else if (expr == "/") {
			int x = stack.pop();
			int y = stack.pop();
			stack.push(y/x);
		}

		else if (expr == "!") {
			while (!stack.isEmpty()) {
				stack.pop();
			}
		}
		else if (expr == ".") {
			System.out.println(stack.pop());
		}
	}

	public void eval(String[] exprs) throws StackUnderflowException {
		for (int i = 0; i <= exprs.length; i++) {
			eval(exprs[i]);
		}
	}

	public void print() throws StackUnderflowException {
	    ArrayStack<Integer> stackCopy = stack;
		if (!stackCopy.isEmpty()) {
		    System.out.println(stackCopy.pop());
		}
	}

	public void loop() throws StackUnderflowException {
		while (true) {
			read();
			print();
		}
	}

	public boolean isInt(String expr) {
	    try { Integer.parseInt(expr);
	    	} catch (NumberFormatException E) {
	    		return false;
	    	}
	    return true;
	}
}