// simple version of $X
// $X(exp);
// $X(exp, context);
// @source http://gist.github.com/3242.txt
function $X (exp, context) {
	context || (context = document);
	var expr = (context.ownerDocument || context).createExpression(exp, function (prefix) {
		return document.createNSResolver(context.documentElement || context).lookupNamespaceURI(prefix) ||
			context.namespaceURI || document.documentElement.namespaceURI || "";
	});

	var result = expr.evaluate(context, XPathResult.ANY_TYPE, null);
		switch (result.resultType) {
			case XPathResult.STRING_TYPE : return result.stringValue;
			case XPathResult.NUMBER_TYPE : return result.numberValue;
			case XPathResult.BOOLEAN_TYPE: return result.booleanValue;
			case XPathResult.UNORDERED_NODE_ITERATOR_TYPE:
				// not ensure the order.
				var ret = [], i = null;
				while (i = result.iterateNext()) ret.push(i);
				return ret;
		}
	return null;
}