41 lines
2.0 KiB
C#
41 lines
2.0 KiB
C#
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using System.Diagnostics;
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using System.Diagnostics.CodeAnalysis;
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using System.Runtime.CompilerServices;
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namespace SJK.Functional;
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public struct Option<T> : IEquatable<Option<T>>
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{
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private readonly T? _value;
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[MemberNotNullWhen(true, nameof(_value))]
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public bool HasValue { get; }
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public static Option<T> None => new(default, false);
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public static Option<T> Some(T value) => new(value, true);
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private Option(T? value, bool hasValue)
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{
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Debug.Assert(!(value is null && hasValue), "Can not create an option with a null value had say it has one");
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_value = value;
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HasValue = hasValue;
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}
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public T? Value => HasValue ? _value : throw new InvalidOperationException("Can not retrive value when there is no value.");
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// [MethodImpl(MethodImplOptions.AggressiveInlining)]
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public TResult Match<TResult>(Func<T, TResult> some, Func<TResult> none) => HasValue ? some(_value) : none();
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// [MethodImpl(MethodImplOptions.AggressiveInlining)]
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public Option<TResult> Map<TResult>(Func<T, TResult> f) => HasValue ? Option<TResult>.Some(f(_value)) : Option<TResult>.None;
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// [MethodImpl(MethodImplOptions.AggressiveInlining)]
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public Option<TResult> Bind<TResult>(Func<T, Option<TResult>> f) => HasValue ? f(_value) : Option<TResult>.None;
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// [MethodImpl(MethodImplOptions.AggressiveInlining)]
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public T OrDefault(T value) => HasValue ? _value : value;
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// [MethodImpl(MethodImplOptions.AggressiveInlining)]
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public T Or(Func<T> factory) => HasValue ? _value : factory();
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public override bool Equals([NotNullWhen(true)] object? obj) => obj is Option<T> other && Equals(other);
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public bool Equals(Option<T> other) => (HasValue == other.HasValue) && (!HasValue || EqualityComparer<T>.Default.Equals(_value, other._value));
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public override int GetHashCode() => HasValue ? EqualityComparer<T>.Default.GetHashCode(_value) : 0;
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public override string ToString() => HasValue ? $"Some({_value})" : $"None<{typeof(T).Name}>()";
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}
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