115 lines
4.2 KiB
C#
115 lines
4.2 KiB
C#
namespace Immutable {
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using System;
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public interface Option<out T> : System.Collections.Generic.IEnumerable<T> {
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U Match_<U>(Func<T, U> Some, Func<U> None);
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bool IsSome { get; }
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bool IsNone { get; }
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}
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public static class Option {
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public static Option<T> Some<T>(T value) => new Types.Some<T>(value);
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public static Option<T> None<T>() => new Types.None<T>();
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private static class Types {
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public class Some<T> : Option<T>, System.Collections.IEnumerable {
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public readonly T value;
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public Some(T value) { this.value = value; }
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public U Match_<U>(Func<T, U> Some, Func<U> None) => Some(value);
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public bool IsSome { get => true; }
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public bool IsNone { get => false; }
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public System.Collections.Generic.IEnumerator<T> GetEnumerator()
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=> value.Singleton().GetEnumerator();
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System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
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=> this.GetEnumerator();
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public override string ToString()
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=> $"Some({value.ToString()})";
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}
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public class None<T> : Option<T>, System.Collections.IEnumerable {
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public None() { }
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public U Match_<U>(Func<T, U> Some, Func<U> None) => None();
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public bool IsSome { get => false; }
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public bool IsNone { get => true; }
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public System.Collections.Generic.IEnumerator<T> GetEnumerator()
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=> System.Linq.Enumerable.Empty<T>().GetEnumerator();
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System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
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=> this.GetEnumerator();
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public override string ToString()
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=> $"None";
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}
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}
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}
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public static class OptionExtensionMethods {
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public static Option<T> Some<T>(this T value) => Option.Some<T>(value);
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public static U Match<T, U>(this Option<T> o, Func<T, U> Some, Func<U> None)
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=> o.Match_(Some: Some,
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None: None);
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public static U Match<T, U>(this Option<T> o, Func<T, U> Some, U None)
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=> o.Match_(Some: Some,
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None: () => None);
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public static Option<U> Map<T, U>(this Option<T> o, Func<T, U> some)
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=> o.Match_(Some: value => some(value).Some(),
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None: () => Option.None<U>());
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public static Option<U> IfSome<T, U>(this Option<T> o, Func<T, U> some)
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=> o.Map(some);
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public static Option<T> If<T>(this T value, Func<T, bool> predicate)
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=> predicate(value) ? value.Some() : Option.None<T>();
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public static Option<ValueTuple<T1, T2>> If<T1, T2>(this ValueTuple<T1, T2> value, Func<T1, T2, bool> predicate)
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=> predicate(value.Item1, value.Item2) ? value.Some() : Option.None<ValueTuple<T1, T2>>();
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public static Option<Tuple<T1, T2>> If<T1, T2>(this Tuple<T1, T2> value, Func<T1, T2, bool> predicate)
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=> predicate(value.Item1, value.Item2) ? value.Some() : Option.None<Tuple<T1, T2>>();
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public static Option<Tuple<T1, T2>> If<T1, T2>(this Option<Tuple<T1, T2>> value, Func<T1, T2, bool> predicate)
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=> value.Bind(val => val.If(predicate));
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public static Option<U> IfSome<T1, T2, U>(this Option<Tuple<T1, T2>> o, Func<T1, T2, U> some)
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=> o.Map(o1o2 => some(o1o2.Item1, o1o2.Item2));
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public static Option<U> IfSome<T1, T2, U>(this Option<ValueTuple<T1, T2>> o, Func<T1, T2, U> some)
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=> o.Map(o1o2 => some(o1o2.Item1, o1o2.Item2));
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public static Option<U> Bind<T, U>(this Option<T> o, Func<T, Option<U>> f)
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=> o.Match_(Some: some => f(some),
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None: () => Option.None<U>());
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public static T Else<T>(this Option<T> o, Func<T> none)
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=> o.Match_(Some: some => some,
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None: none);
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public static T Else<T>(this Option<T> o, T none)
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=> o.Match_(Some: some => some,
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None: () => none);
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public static Option<T> Else<T>(this Option<T> o, Func<Option<T>> none)
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=> o.Match_(Some: value => value.Some(),
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None: none);
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public static T ElseThrow<T>(this Option<T> o, Func<Exception> none)
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=> o.Match_(Some: value => value,
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None: () => throw none());
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public static T ElseThrow<T>(this Option<T> o, Exception none)
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=> o.Match_(Some: value => value,
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None: () => throw none);
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}
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} |