public static boolean isValidType(String type, Symtab st) {
		if (!(type.equals("int")
				|| type.equals("decimal")
				|| type.equals("String")
				|| type.equals("message")
				|| type.equals("boolean") || type.startsWith("list") || st.lookup(type) != null))
			return false;
		if (type.startsWith("list"))
			return isValidType(getListType(type), st);
		return true;
	}