73 lines
2.5 KiB
C#
73 lines
2.5 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using Mutable = System.Collections.Generic;
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public static class Func {
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// supply 1 argument to function of 2 arguments
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public static Func<B,C> Partial<A,B,C>(this Func<A,B,C> f, A a) {
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return b => f(a, b);
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}
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// supply 1 argument to function of 3 arguments
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public static Func<B,C,D> Partial<A,B,C,D>(this Func<A,B,C,D> f, A a) {
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return (b, c) => f(a, b, c);
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}
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// supply 2 arguments to function of 3 arguments
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public static Func<C,D> Partial<A,B,C,D>(this Func<A,B,C,D> f, A a, B b) {
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return c => f(a, b, c);
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}
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// break down function of 2 arguments to require 2 successive 1-argument calls
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public static Func<A,Func<B,C>> Curry<A,B,C>(this Func<A,B,C> f) {
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return a => b => f(a, b);
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}
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// break down function of 3 arguments to require 2 successive 1-argument calls
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public static Func<A,Func<B,Func<C,D>>> Curry<A,B,C,D>(this Func<A,B,C,D> f) {
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return a => b => c => f(a, b, c);
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}
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public static Func<A, B> YMemoize<A, B>(this Func<Func<A, B>, A, B> f) where A : IEquatable<A> {
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var d = new Mutable.Dictionary<A, B>();
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// I'm too lazy to implement the Y combinator…
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Func<A, B> memf = null;
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memf = a => {
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if (d.TryGetValue(a, out var b)) {
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return b;
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} else {
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var calcB = f(memf, a);
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d.Add(a, calcB);
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return calcB;
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}
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};
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return memf;
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}
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public static Func<A, B, C> YMemoize<A, B, C>(this Func<Func<A, B, C>, A, B, C> f) where A : IEquatable<A> where B : IEquatable<B>
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=> (a, b) => YMemoize<ValueTuple<A, B>, C>(
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(memf, ab) =>
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f((aa, bb) => memf((aa, bb)),
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ab.Item1,
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ab.Item2))
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((a, b));
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public static Func<A, B> Memoize<A, B>(this Func<A, B> f) where A : IEquatable<A>
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=> YMemoize<A, B>((memf, aa) => f(aa));
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public static Func<A, B, C> Memoize<A, B, C>(this Func<A, B, C> f) where A : IEquatable<A> where B : IEquatable<B>
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=> YMemoize<A, B, C>((memf, aa, bb) => f(aa, bb));
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public static B Memoized<A, B>(this Func<A, B> f, A a) where A : IEquatable<A>
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=> f.Memoize()(a);
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public static C Memoized<A, B, C>(this Func<A, B, C> f, A a, B b) where A : IEquatable<A> where B : IEquatable<B>
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=> f.Memoize()(a, b);
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public static B YMemoized<A, B>(this Func<Func<A, B>, A, B> f, A a) where A : IEquatable<A>
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=> f.YMemoize()(a);
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public static C YMemoized<A, B, C>(this Func<Func<A, B, C>, A, B, C> f, A a, B b) where A : IEquatable<A> where B : IEquatable<B>
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=> f.YMemoize()(a, b);
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} |