Regalis11
112 lines
3.7 KiB
C#
112 lines
3.7 KiB
C#
#nullable enable
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using System;
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using System.Diagnostics.CodeAnalysis;
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namespace Barotrauma
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{
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public readonly struct Option<T> where T : notnull
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{
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private readonly bool hasValue;
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private readonly T? value;
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private Option(bool hasValue, T? value)
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{
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this.hasValue = hasValue;
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this.value = value;
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}
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public bool IsSome() => hasValue;
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public bool IsNone() => !IsSome();
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public bool TryUnwrap<T1>([NotNullWhen(returnValue: true)] out T1? outValue) where T1 : T
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{
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bool hasValueOfGivenType = false;
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outValue = default;
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if (hasValue && value is T1 t1)
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{
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hasValueOfGivenType = true;
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outValue = t1;
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}
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return hasValueOfGivenType;
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}
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public bool TryUnwrap([NotNullWhen(returnValue: true)] out T? outValue)
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=> TryUnwrap<T>(out outValue);
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public Option<TType> Select<TType>(Func<T, TType> selector) where TType : notnull
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=> TryUnwrap(out T? selfValue) ? Option.Some(selector(selfValue)) : Option.None;
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public Option<TType> Bind<TType>(Func<T, Option<TType>> binder) where TType : notnull
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=> TryUnwrap(out T? selfValue) ? binder(selfValue) : Option.None;
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public T Fallback(T fallback)
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=> TryUnwrap(out var v) ? v : fallback;
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public Option<T> Fallback(Option<T> fallback)
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=> IsSome() ? this : fallback;
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public static Option<T> Some(T value)
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=> typeof(T) switch
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{
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var t when t == typeof(bool)
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=> throw new Exception("Option type rejects booleans"),
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{IsConstructedGenericType: true} t when t.GetGenericTypeDefinition() == typeof(Option<>)
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=> throw new Exception("Option type rejects nested Option"),
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{IsConstructedGenericType: true} t when t.GetGenericTypeDefinition() == typeof(Nullable<>)
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=> throw new Exception("Option type rejects Nullable"),
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_
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=> new Option<T>(hasValue: true, value: value ?? throw new Exception("Option type rejects null"))
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};
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public override bool Equals(object? obj)
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=> obj switch
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{
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Option<T> otherOption when otherOption.IsNone()
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=> IsNone(),
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Option<T> otherOption when otherOption.TryUnwrap(out var otherValue)
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=> ValueEquals(otherValue),
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T otherValue
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=> ValueEquals(otherValue),
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_
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=> false
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};
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public bool ValueEquals(T otherValue)
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=> TryUnwrap(out T? selfValue) && selfValue.Equals(otherValue);
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public override int GetHashCode()
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=> TryUnwrap(out T? selfValue) ? selfValue.GetHashCode() : 0;
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public static bool operator ==(Option<T> a, Option<T> b)
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=> a.Equals(b);
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public static bool operator !=(Option<T> a, Option<T> b)
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=> !(a == b);
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public static Option<T> None()
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=> default;
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public static implicit operator Option<T>(in Option.UnspecifiedNone _)
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=> None();
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public override string ToString()
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=> TryUnwrap(out var selfValue)
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? $"Some<{typeof(T).Name}>({selfValue})"
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: $"None<{typeof(T).Name}>";
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}
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public static class Option
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{
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public static Option<T> Some<T>(T value) where T : notnull
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=> Option<T>.Some(value);
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public static UnspecifiedNone None
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=> default;
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public readonly ref struct UnspecifiedNone
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{
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}
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}
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} |