cs-extensions/exasynctools/Maybes.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace Tools.Maybes
{
    static class test
    {
        public static void maybe()
        {
            var result = Maybe.Some(false);

            if(result)
            {
                bool value = result;

            }
            else
            {

            }

            result.Match(Some: value =>
            {
                return 10;
            }, None: () =>
            {
                return 0;
            });

            var valresult = ValueMaybe.Some(10.1f);
            if(valresult)
            {
                float res = valresult;
            }
            else
            {

            }

            valresult.Match(Some: value =>
            {
                return value * 2;
            }, None: () =>
            {
                return 0;
            });
        }
       /* public void tresult()
        {
            var result = Result.Ok("hi");
        }*/
    }

    public static class ValueMaybe
    {
        public static ValueMaybe<T> Some<T>(T value)
            => new ValueMaybe<T>(value, true);
        public static ValueMaybe<T> None<T>()
            => new ValueMaybe<T>(default, false);
    }
    public readonly struct ValueMaybe<T>
    {
        private readonly T value;
        private readonly bool hasValue;

        public bool Equals(ValueMaybe<T> other)
        {
            return other.hasValue == this.hasValue && (ReferenceEquals(value, other.value) || (value?.Equals(other.value) ?? false));
        }
        public override int GetHashCode()
        {
            return hasValue ? Math.Abs(value?.GetHashCode() ?? 0) : -1;
        }

        public override bool Equals(object obj)
        {
            return (obj is ValueMaybe<T> some && Equals(some)) || (hasValue && obj is T val && (ReferenceEquals(val, value) || (value?.Equals(val) ?? false)));
        }

        internal ValueMaybe(T value, bool hasValue)
        {
            this.hasValue = hasValue;
            this.value = value;
        }

        public static bool operator true(ValueMaybe<T> some)
            => some.hasValue;
        public static bool operator false(ValueMaybe<T> some)
            => !some.hasValue;

        public static implicit operator T(ValueMaybe<T> input)
            => input.hasValue ? input.value : throw new InvalidCastException("No value");
        public static implicit operator ValueMaybe<T>(T input)
            => ValueMaybe.Some(input);

        public T Value => value;
        public bool HasValue => hasValue;

        public bool TryGetValue(out T value)
        {
            if(HasValue)
            {
                value = Value;
                return true;
            }
            value = default;
            return false;
        }

        public void Match(Action<T> Some=null, Action None=null)
        {
            if (hasValue)
                Some?.Invoke(value);
            else
                None?.Invoke();
        }
        public V Match<V>(Func<T, V> Some=null, Func<V> None=null)
        {
            if(hasValue)
            {
                if (Some != null) return Some(value);
                else return default;
            }
            else
            {
                if (None != null) return None();
                else return default;
            }
        }

        public static bool operator ==(ValueMaybe<T> left, ValueMaybe<T> right)
        {
            return left.Equals(right);
        }

        public static bool operator !=(ValueMaybe<T> left, ValueMaybe<T> right)
        {
            return !(left == right);
        }
    }

    public sealed class Some<T> : Maybe<T>
    {
        public override T Value { get; }
        internal Some(T value)
        {
            Value = value;
        }

        public override bool Equals(object obj)
        {
            return obj is Some<T> some && (ReferenceEquals(some.Value, Value) || (some.Value?.Equals(Value) ?? false));
        }
        public override int GetHashCode()
        {
            return Math.Abs(Value?.GetHashCode() ?? 0);
        }

        public override string ToString()
        {
            return "Some(" + (Value?.ToString() ?? "null") + ")";
        }
    }
    public sealed class None<T> : Maybe<T>
    {
        internal None() { }

        public override bool Equals(object obj)
        {
            return obj is None<T>;
        }
        public override int GetHashCode()
        {
            return -1;
        }

        public override string ToString()
        {
            return "None";
        }
    }
    public static class Maybe
    {
        public static Maybe<T> Some<T>(T value)
            => new Some<T>(value);

        public static Maybe<T> None<T>()
            => new None<T>();
    }
    public abstract class Maybe<T>
    {
        public static bool operator true(Maybe<T> input)
            => input is Some<T>;
        public static bool operator false(Maybe<T> input)
            => input is None<T>;

        public override bool Equals(object obj)
        {
            throw new NotImplementedException();
        }
        public override int GetHashCode()
        {
            throw new NotImplementedException();
        }
        public override string ToString()
        {
            throw new NotImplementedException();
        }

        public static bool operator ==(Maybe<T> left, T right)
            => left.HasValue && (left == Maybe.Some(right));
        public static bool operator !=(Maybe<T> left, T right)
            => !(left == right);
        public static bool operator ==(Maybe<T> left, Maybe<T> right)
        {
            return ReferenceEquals(left, right) || (left?.Equals(right) ?? false);
        }
        public static bool operator !=(Maybe<T> left, Maybe<T> right)
            => !(left == right);

        public static implicit operator T(Maybe<T> some) => some is Some<T> thing ? thing : throw new InvalidCastException("No value");
        public static implicit operator Maybe<T>(T some) => new Some<T>(some);

        public virtual T Value => (T)this;
        public bool HasValue => this is Some<T>;

        public bool TryGetValue(out T value)
        {
            if(this is Some<T> thing)
            {
                value = thing.Value;
                return true;
            }
            value = default;
            return false;
        }

        public void Match(Action<T> Some = null, Action None = null)
        {
            if (this is Some<T> some)
            {
                Some?.Invoke(some.Value);
            }
            else if (this is None<T> none)
                None?.Invoke();
            throw new InvalidOperationException("Maybe is neither some nor none.");
        }
        public V Match<V>(Func<T, V> Some = null, Func<V> None = null)
        {
            if (this is Some<T> some)
            {
                if (Some == null) return default;
                else return Some(some.Value);
            }
            else if (this is None<T> none)
            {
                if (None == null) return default;
                else
                    return None();
            }
            throw new InvalidOperationException("Maybe is neither some nor none.");
        }
    }
#if REWORK && false
    public class Ok<T,E> : Result<T,E>
    {
        public override T Value { get; }
        public Ok(T value)
        {
            Value = value;
        }
    }
    public class Err<T,E> : Result<T,E>
    {
        public override E Error { get; }
        public Err(E exception)
        {
            Error = exception;
        }
    }
    public static class Result
    {
        public static Ok<T, E> Ok<T, E>(T value)
            => new Ok<T, E>(value);
        public static Err<T, E> Err<T, E>(E value)
            => new Err<T, E>(value);
    }
    public abstract class Result<T,E>
    {
        public static bool operator true(Result<T, E> input)
            => input is Ok<T, E>;
        public static bool operator false(Result<T, E> input)
            => input is Err<T, E>;

        public virtual T Value => (T)this;
        public virtual E Error => (E)this;


        public bool TryGetValue(out T value)
        {
            if (this is Ok<T, E> thing)
            {
                value = thing.Value;
                return true;
            }
            value = default;
            return false;
        }
        public bool TryGetError(out E value)
        {
            if (this is Err<T, E> thing)
            {
                value = thing.Error;
                return true;
            }
            value = default;
            return false;
        }

        public static implicit operator T(Result<T, E> validResult) => validResult is Ok<T, E> ok ? ok.Value : throw new InvalidCastException("No value");
        public static implicit operator E(Result<T, E> invalidResult) => invalidResult is Err<T, E> ok ? ok.Error : throw new InvalidCastException("No exception");
    }
#endif
}