/* File: Arithmetic.java
   For CMSC 220, Fall 1998, U. Wolz, October 1998
*/

import javax.swing.*;

/* This class implements a two bit binary adder. For example it can handle 
   an addition such as 10 + 11. 
   
   MODIFY INSTRUCTIONS: Modify this class so that it implements a four bit 
   adder, for example it should handle addition such as 1010 + 0100.
   
   Read through the code, answer the questions below and then answer the following:
   
   1. Why store the values of the numbers as booleans instead of int or as 1 & 0. Discuss
      the tradeoffs.
*/

class Arithmetic {
// Two numbers are received from a user via SimpleGUI methods. These numbers, a and b, are stored
// as boolean values.
// Data fields
	// The input number "a"	
	private boolean a1; // the high order bit (2 to the power of 1)
	private boolean a0; // the low order bit (2 to the power of 0)
	
	
	// The input number "b"
	private boolean b1; // the high order bit (2 to the power of 1)
	private boolean b0; // the low order bit (2 to the power of 2)
	
	
	/* Asks for the numbers a and b in turn. Displays the full string of binary digits for each.
	   QUESTION: what is the purpose of passing the result of getInt to dTob? Why not simply
			     ask the user for boolean values, why use digits instead?
	   QUESTION: what are the values 0,1 for in the argument list for getInt.
	*/ 
	public void getDigits() {
		// QUESTION: explain what happens when the following statement is executed.
		a1 = dTob( Integer.parseInt(JOptionPane.showInputDialog(null, "a1 digit(0,1): ")));
		a0 = dTob( Integer.parseInt(JOptionPane.showInputDialog(null, "a0 digit(0,1): ")));
		
		JOptionPane.showMessageDialog(null, "a = " + bTod(a1) + bTod(a0));
		
		b1 = dTob(Integer.parseInt(JOptionPane.showInputDialog(null, "b1 digit(0,1): ")));
		b0 = dTob(Integer.parseInt(JOptionPane.showInputDialog(null, "b0 digit(0,1): ")));
		JOptionPane.showMessageDialog(null, "b = " + bTod(a1) + bTod(a0));
	}
	
	
	/* Creates a FullAdder instance, calculates the low order sum, then uses the low order
	   carry as input to reset the adder to calculate the high order result.
	   
	   QUESTION: why is the first carry argument set to "false".
	   QUESTION: why must the result of the low order sum be stored, why don't any of the other 
	   			 adder results need to be stored locally?
	*/ 
	   
	public void showResult() {
		FullAdder f = new FullAdder(b0,a0, false);
		
		boolean sumOut1 = f.sum();
		
		f.setBits(b1,a1, f.carry());
		
		// QUESTION: explain what happens when this statement is executed.
		JOptionPane.showMessageDialog(null, "Result " +  bTod(f.carry()) + bTod(f.sum()) + bTod(sumOut1));
	}
	
	// This takes an integer (assumed to be 1 or 0) and returns true if the integer is 
	// equal to 1.
	// QUESTION: Explain why this method does not require an if then statement.
	private static boolean dTob(int i) {
		return (i == 1);
	}
	
	// This takes a boolean value and returns 0 for false, 1 for true.
	// QUESTION: Explain why this method requires an if then when dTob didn't.
	
	private int bTod(boolean b) {
		if (b) return 1;
		else return 0;		
	}
	
		
}