Declarative Programming--Unifying Form And Web Development

// Copyright (c) 2004 Marc Clifton.  All Rights Reserved

using System;
using System.Globalization;
using System.Web.UI.WebControls;

using MyXaml;

namespace declarativeWeb
{
	public class SimpleCalc
	{
		private bool cleared;
		private string lastOp;
		private string lastValue;
		private NumberFormatInfo formatProvider;
	
		[MyXamlAutoInitialize] private TextBox display=null;

		public SimpleCalc()
		{
			cleared=true;
			lastOp=String.Empty;
			lastValue=String.Empty;

			formatProvider=new NumberFormatInfo();
			formatProvider.NumberDecimalDigits=2;
		}

		public void OnClear(object sender, EventArgs e)
		{
			display.Text="0.00";
			cleared=true;
			lastOp=String.Empty;
			lastValue=String.Empty;
		}

		public void OnClearEntry(object sender, EventArgs e)
		{
			display.Text="0.00";
			cleared=true;
		}

		public void OnDigit(object sender, EventArgs e)
		{
			Button btn=(Button)sender;
			if (cleared)
			{
				display.Text=btn.Text;
				cleared=false;
			}
			else
			{
				display.Text=display.Text+btn.Text;
			}
		}

		public string ProcessLastOp(string val)
		{
			double d=0;
			switch(lastOp)
			{
				case "+":
				{
					d=Convert.ToDouble(lastValue) + Convert.ToDouble(val);
					break;
				}
				case "-":
				{
					d=Convert.ToDouble(lastValue) - Convert.ToDouble(val);
					break;
				}
				case "*":
				{
					d=Convert.ToDouble(lastValue) * Convert.ToDouble(val);
					break;
				}
				case "/":
				{
					if (Convert.ToDouble(val) != 0.0)
					{
						d=Convert.ToDouble(lastValue) / Convert.ToDouble(val);
					}
					break;
				}
			}
			lastValue=d.ToString("N", formatProvider);
			return lastValue;
		}

		public void OnAdd(object sender, EventArgs e)
		{
			if (lastValue==String.Empty)
			{
				lastValue=display.Text;
			}
			else
			{
				lastValue=ProcessLastOp(display.Text);
				display.Text=lastValue;
			}
			lastOp="+";
			cleared=true;
		}

		public void OnSubtract(object sender, EventArgs e)
		{
			if (lastValue==String.Empty)
			{
				lastValue=display.Text;
			}
			else
			{
				lastValue=ProcessLastOp(display.Text);
				display.Text=lastValue;
			}
			lastOp="-";
			cleared=true;
		}

		public void OnMultiply(object sender, EventArgs e)
		{
			if (lastValue==String.Empty)
			{
				lastValue=display.Text;
			}
			else
			{
				lastValue=ProcessLastOp(display.Text);
				display.Text=lastValue;
			}
			lastOp="*";
			cleared=true;
		}

		public void OnDivide(object sender, EventArgs e)
		{
			if (lastValue==String.Empty)
			{
				lastValue=display.Text;
			}
			else
			{
				lastValue=ProcessLastOp(display.Text);
				display.Text=lastValue;
			}
			lastOp="/";
			cleared=true;
		}

		public void OnEqual(object sender, EventArgs e)
		{
			if (lastValue != String.Empty)
			{
				display.Text=ProcessLastOp(display.Text);
				lastValue=String.Empty;
				lastOp=String.Empty;
				cleared=true;
			}
		}
	}
}