function addDigit(value)
{
	
	document.calculator.expression.value = document.calculator.expression.value + value;
	document.calculator.result.value="";
}

function addMathOp(value)
{
	
	if(document.calculator.result.value != "" && document.calculator.expression.value == "")
	{
		var str = document.calculator.result.value;
		if(str.substring(0, 8) == " = Could" || str.substring(0, 7) == " = NAN")
			document.calculator.expression.value = document.calculator.expression.value + value;
		else		
			document.calculator.expression.value = str.substring(3, str.length) + value;
	}
	else
	document.calculator.expression.value = document.calculator.expression.value + value;

	document.calculator.result.value="";
}

function addFunc(value)
{
	
	if(document.calculator.result.value != "" && document.calculator.expression.value == "")
	{
		var str = document.calculator.result.value;
		if(str.substring(0, 8) == " = Could" || str.substring(0, 7) == " = NAN")
			document.calculator.expression.value = document.calculator.expression.value + value;
		else	
			document.calculator.expression.value = value+"("+str.substring(3, str.length)+")";
	}
	else
	document.calculator.expression.value = document.calculator.expression.value + value;

	document.calculator.result.value="";
}

function doC()
{
	
	document.calculator.expression.value ="";
	document.calculator.result.value="";
}


function doClear()
{
	
	document.calculator.expression.value ="";
}