63 lines
3.0 KiB
C#
63 lines
3.0 KiB
C#
using System;
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using System.Collections.Immutable;
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public sealed class ImmutableDictionaryValueLens<TKey, TValue, Whole> : ILens<TValue, Whole> {
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public readonly Func<ImmutableDictionary<TKey, TValue>, Whole> wrap;
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public readonly ImmutableDictionary<TKey, TValue> oldDictionary;
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public readonly TKey oldKey;
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public ImmutableDictionaryValueLens(Func<ImmutableDictionary<TKey, TValue>, Whole> wrap, ImmutableDictionary<TKey, TValue> oldDictionary, TKey oldKey) {
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// TODO: check that key exists.
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this.wrap = wrap;
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this.oldDictionary = oldDictionary;
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this.oldKey = oldKey;
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}
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// Put methods with the following signature here to focus on sub-parts of the list as needed.
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// public ILens<ImmutableList<T>,Whole> sub-part => oldHole.sub-part.ChainLens(value => oldHole.with-sub-part(value));
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public Whole Update(Func<TValue, TValue> update) {
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var oldValue = oldDictionary[oldKey];
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return wrap(oldDictionary.SetItem(oldKey, update(oldValue)));
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}
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public ImmutableDictionaryValueLens<TKey, TValue, Whole> UpdateKey(Func<TKey, TKey> update) {
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var newKey = update(oldKey);
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return new ImmutableDictionaryValueLens<TKey, TValue, Whole>(
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wrap,
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oldDictionary.Remove(oldKey).Add(newKey, oldDictionary[oldKey]),
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newKey);
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}
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}
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public sealed class ImmutableDictionaryLens<TKey, TValue, Whole> : ILens<ImmutableDictionary<TKey, TValue>, Whole> {
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public readonly Func<ImmutableDictionary<TKey, TValue>, Whole> wrap;
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public readonly ImmutableDictionary<TKey, TValue> oldHole;
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public ImmutableDictionaryLens(Func<ImmutableDictionary<TKey, TValue>, Whole> wrap, ImmutableDictionary<TKey, TValue> oldHole) {
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// TODO: check that key exists.
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this.wrap = wrap;
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this.oldHole = oldHole;
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}
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// Put methods with the following signature here to focus on sub-parts of the list as needed.
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public ImmutableDictionaryValueLens<TKey, TValue, Whole> this[TKey key] {
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get => new ImmutableDictionaryValueLens<TKey, TValue, Whole>(wrap, oldHole, key);
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}
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public Whole Update(Func<ImmutableDictionary<TKey, TValue>, ImmutableDictionary<TKey, TValue>> update) {
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return wrap(update(oldHole));
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}
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}
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public static class ImmutableDictionaryLensExtensionMethods {
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public static ImmutableDictionaryLens<TKey, TValue, ImmutableDictionary<TKey, TValue>> lens<TKey, TValue>(this ImmutableDictionary<TKey, TValue> d)
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=> new ImmutableDictionaryLens<TKey, TValue, ImmutableDictionary<TKey, TValue>>(x => x, d);
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public static ImmutableDictionaryValueLens<TKey, TValue, Whole> UpdateKey<TKey, TValue, Whole, Whole>(this ImmutableDictionaryValueLens<TKey, TValue, Whole> lens, TKey newKey)
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=> lens.UpdateKey(oldKey => newKey);
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// This would need an IFocusable<TValue> constraint which is hard to get
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//public static ILens<ImmutableDictionary<TKey, ?>, Whole> ChainLens<TKey, Whole>(this ImmutableDictionary<TKey, ?> hole, System.Func<ImmutableDictionary<TKey, ?>, Whole> wrap)
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// => new ImmutableDictionaryLens<TKey, ?, Whole>(wrap: wrap, oldHole: hole);
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} |