public function evaluate(Context $context, $expression) {
		if(is_numeric($expression)) {
			$expression = (string)$expression;
		}
		if(! isset($context->view->lexers[$expression]) ) {
			$lexer = new Lexer($expression);
			$context->view->lexers[$expression] = & $lexer;
			$lexer->parse($context);
		} else {
			$lexer = & $context->view->lexers[$expression];
		}

		$result = $lexer->evaluate($context);
		return $result;
	}