Introduce Result<T,E>, an either monad

csharp/Lib/Utils/Result.cs

@@ -0,0 +1,104 @@
+namespace InnovEnergy.Lib.Utils;
+
+
+// TODO: discriminated union
+public abstract record Result<T> 
+{
+    public sealed record Success(T      Value) : Result<T>;
+    public sealed record Failure(String Error) : Result<T>;
+
+    public Boolean IsError => this is Failure;
+    public Boolean IsOk    => this is Success;
+    
+    public static implicit operator Result<T>(T t)      => new Success(t);
+    public static implicit operator Result<T>(String e) => new Failure(e);
+}
+
+public abstract record Result<T, E>
+{
+    public sealed record Success(T Value) : Result<T, E>;
+    public sealed record Failure(E Error) : Result<T, E>;
+
+    public Boolean IsError => this is Failure;
+    public Boolean IsOk    => this is Success;
+    
+    public static implicit operator Result<T, E>(T t) => new Success(t);
+    public static implicit operator Result<T, E>(E e) => new Failure(e);
+    
+    public R Map<R>(Func<T, R> onSuccess, Func<E, R> onFailure) => this switch
+    {
+        Success s => onSuccess(s.Value),
+        Failure f => onFailure(f.Error),
+        _         => throw new ArgumentOutOfRangeException()
+    };
+
+    public Result<R, E> OnSuccess<R>(Func<T, R> onOk) => this switch
+    {
+        Success s => onOk(s.Value),
+        Failure f => f.Error,
+        _         => throw new ArgumentOutOfRangeException()
+    };
+
+    public Result<T, R> OnFailure<R>(Func<E, R> onError) => this switch
+    {
+        Success s => s.Value,
+        Failure f => onError(f.Error),
+        _         => throw new ArgumentOutOfRangeException()
+    };
+}
+
+public static class Result
+{
+    public static Result<T, Exception> Try<T>(Func<T> func)
+    {
+        try
+        {
+            return func();
+        }
+        catch (Exception e)
+        {
+            return e;
+        }
+    }
+
+    public static String? GetError<T>(this Result<T> r) 
+    {
+        return r is Result<T>.Failure err 
+             ? err.Error 
+             : null;
+    }
+}
+
+public static class ResultClass
+{
+    public static T? GetValue<T>(this Result<T> r) where T : class
+    {
+        return r is Result<T>.Success ok 
+             ? ok.Value 
+             : null;
+    }
+
+    public static E? GetError<T, E>(this Result<T, E> r) where E : class
+    {
+        return r is Result<T, E>.Failure err
+             ? err.Error
+             : null;
+    }
+}
+
+public static class ResultStruct
+{
+    public static T? GetValue<T>(this Result<T> r) where T : struct
+    {
+        return r is Result<T>.Success ok 
+             ? ok.Value 
+             : null;
+    }
+    
+    public static E? GetError<T, E>(this Result<T, E> r) where E : struct
+    {
+        return r is Result<T,E>.Failure err 
+             ? err.Error 
+             : null;
+    }
+}

csharp/Lib/Utils/WIP/Result.cs

@@ -1,9 +0,0 @@
-namespace InnovEnergy.Lib.Utils.WIP;
-
-
-// TODO: discriminated union
-public abstract record Result
-{
-    public sealed record Ok(Object Result) : Result;
-    public sealed record Error(String Message) : Result;
-}