@Test
public void functionTest2() {

  String ruleCode = "set col: speed value: time_diff(now(), add_time(now(), 1, 'hour'))";
  RuleVisitorParser parser = new RuleVisitorParser();
  Set setRule = (Set) parser.parse(ruleCode);
  ExprEval exprEval = ((Expr)setRule.getValue()).eval(null);
  System.out.println(exprEval.toString());
  assertEquals("3600", exprEval.asString().substring(0,4));
}