@RequestMapping(value = "/evaluate", method = RequestMethod.GET)
@ResponseBody
public Map<String, Object> evaluate(HttpServletRequest request) throws UnknownFunctionException, UnparsableExpressionException {
String query = request.getParameter("query");
Calculable calc = new ExpressionBuilder(query).build();
return Collections.singletonMap(query, (Object) calc.calculate());
}