How to cast(or convert) to some type ?

[Himmelt]

Hello!

Dictionary<string, Func<object>> varMap = new() {
    ["sec"] = () => DateTime.Now.Second
};

var calc = Funny.WithFunction("vars", (string name) => varMap[name]()).BuildForCalcConstant();

var result = calc.Calc("1 + vars('sec')");

Console.WriteLine(result);

These codes will cause NFun.Exceptions.FunnyParseException:“Invalid operator call argument: +(T0, T0)->T0. Expected: T0”.

I want to cast or convert the object{int} type to integer or real type, but I didn't found the usage in the examples.

Can you show me how to do this ?

Thanks !

[tmteam]

Hi! As i see here - the func in the dictionary returns object, that means that vars function returns any type (object, in terms of C#)

But as far as Nfun has strict type system - it denies to sum any and number item, so you have the error.

to show it more clearly - lets simplify your code (in terms of types) like this:

var calc = Funny.WithFunction<string, object> ("vars", (string name) => new object()).BuildForCalcConstant();
var result = calc.Calc("1 + vars('sec')"); 

here you can see, that it is impossible to sum 1 and new object().

so, the solution is to change Func<object> to Func<int>:

        Dictionary<string, Func<int>> varMap = new() {
            ["sec"] = () => DateTime.Now.Second
        };
        var calc = Funny.WithFunction("vars", (string name) => varMap[name]()).BuildForCalcConstant();
        var result = calc.Calc("1 + vars('sec')");
        Console.WriteLine(result);

or to use named typed function:

        var calc = Funny.WithFunction("sec", () => DateTime.Now.Second).BuildForCalcConstant();
        var result = calc.Calc("1 + sec()");
        Console.WriteLine(result);