public void CustomStaticIterator() { // Creating some example lambda to run our expression on. var hl = @"foo howdy:XXX"; var lambda = new Parser(hl).Lambda().Children; // Creating an expression, and evaluating it on above lambda. Iterator.AddStaticIterator("^^", (identity, input) => { return(input.Where(x => x.GetEx <string>() == "XXX")); }); var x = new Expression("../**/^^"); var result = x.Evaluate(lambda.First()).ToList(); Assert.Single(result); Assert.Equal("howdy", result.First().Name); }