public boolean isFactor(String input, int pos)
	{

		if(isLetter(input,pos))	{return true;}
		
		if(isParen(input,pos))
		{
			pos = takeParen(input,pos);
			if(isExpression(input,pos)){
				pos = takeExpression(input,pos);
				if(isCloseParen(input,pos)){return true;}
			}
			
		}
		return false;
	}