New Results API

[sys27]

API:

public abstract class Result
{
    public static implicit operator Result(NumberValue n) => new NumberResult(n);
    public static implicit operator NumberValue(NumberResult r) => r.Number;
    // ...

    public bool TryGetNumber(out NumberValue number);
    // ...

    public NumberValue Number => ...; // throw exception
    // ...

    public sealed class NumberResult : Result
    {
        public override string ToString() => ...;

        public NumberValue Number => ...;
    }
    
    public sealed class AngleResult : Result
    {
        public override string ToString() => ...;

        public AngleValue Angle => ...;
    }
    
    // ...
}

Usage:

// ...
var processor = new Processor();
var result = processor.Solve("1 + 2");
Console.WriteLine(result.Number);

// or 
var processor = new Processor();
var result = processor.Solve("1 + 2");
if (result.TryGetNumber(out var number))
    Console.WriteLine(number);

// or 
var processor = new Processor();
var result = processor.Solve("1 + 2");
if (result is NumberResult numberResult)
    Console.WriteLine(numberResult.Number);

// or 
var processor = new Processor();
var result = processor.Solve("1 + 2");
Console.WriteLine(result);