using uCalcSoftware;

var uc = new uCalc();
uc.DefineFunction("MyRound(x)", uc.ItemOf("Floor").FunctionAddress);
Console.WriteLine(uc.Eval("MyRound(2.5)"));

uc.ItemOf("MyRound").SetFunctionAddress(uc.ItemOf("Ceil").FunctionAddress);
Console.WriteLine(uc.Eval("MyRound(2.5)"));