69 lines
2.7 KiB
C#
69 lines
2.7 KiB
C#
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using System.Diagnostics.CodeAnalysis;
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namespace SJK.Functional;
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public readonly struct Option<T> : IOption<T>,
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IOption<Option<T>, T>//,
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// K<Option,T,Option<T>>,
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// IEquatable<Option<T>>
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{
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private readonly T? _value;
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private Option(T? value, bool hasValue)
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{
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_value = value;
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HasValue = hasValue;
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}
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public static Option<T> None => new Option<T>(default!,false);
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public T? Value => _value;
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[MemberNotNullWhen(true, nameof(HasValue), nameof(_value))]
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[MemberNotNullWhen(true, nameof(HasValue), nameof(Value))]
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public bool HasValue {get;init;}
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public static Option<T> Some(T value) => new Option<T>(value, true);
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// public bool Equals(Option<T> other)
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// {
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// return other.HasValue == HasValue && EqualityComparer<T>.Default.Equals(_value,other._value);
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// }
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public TResult Match<TResult>(Func<T, TResult> onSome, Func<TResult> onNone) => HasValue ? onSome(_value) : onNone();
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// public TOption Map<TResult, TOption>(Func<T, TResult> f) where TOption : IOption<TOption, TResult> => HasValue ? TOption.Some(f(Value)) : TOption.None;
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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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public Option<TResult> Map<TResult>(Func<T,TResult> f) => HasValue ? Option<TResult>.Some(f(_value)) : Option<TResult>.None;
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public Option<TResult> Bind<TResult>(Func<T,Option<TResult>> f) => HasValue ? f(_value) : Option<TResult>.None;
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public static implicit operator Option<T> (T? nullable) => nullable is not null?Some(nullable) : None;
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public static implicit operator T? (Option<T> nullable) => nullable.Value;
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// public static implicit operator bool(Option<T> option) => option.HasValue;
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public static bool operator true(Option<T> value) => value.HasValue;
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public static bool operator false(Option<T> value) => !value.HasValue;
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public override int GetHashCode()=> HasValue? _value.GetHashCode() : 0;
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public override string ToString() => HasValue ? $"Some({_value})" : $"None<{typeof(T).Name}>()";
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// public override bool Equals([NotNullWhen(true)] object? obj) => obj is Option<T> option?Equals(option):false;
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// public T Or(Func<T> aDefault) => HasValue?_value:aDefault();
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// public T OrDefault(T aDefault) => HasValue?_value:aDefault;
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// IOption<TResult> IOption<T>.Map<TResult>(Func<T, TResult> f) => Match<IOption<TResult>>(onSome => Some<TResult>.Of(f(onSome)), ()=>None<TResult>.Of);
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// public bool TryGetValue(out T value)
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// {
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// if (HasValue)
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// {
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// value = Value;
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// return true;
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// }
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// value = default;
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// return false;
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// }
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}
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