MicroUtils/Functional.cs at master · microsoftenator2022/MicroUtils · GitHub

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using System;
using System.Runtime.CompilerServices;

namespace MicroUtils
{
    public readonly record struct Unit();

    /// <summary>
    /// Functional utilities
    /// </summary>
    public static partial class Functional
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static U Upcast<T, U>(this T t) where T : U => t;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static object Box<T>(this T t) where T : notnull => t;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static T Identity<T>(T x) => x;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void Ignore<T>(T _) { }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<B, C> PartialApply<A, B, C>(Func<A, B, C> f, A a) =>
            (B b) => f(a, b);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<B, C, D> PartialApply<A, B, C, D>(Func<A, B, C, D> f, A a) =>
            (B b, C c) => f(a, b, c);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<B, C, D, E> PartialApply<A, B, C, D, E>(Func<A, B, C, D, E> f, A a) =>
            (B b, C c, D d) => f(a, b, c, d);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<B, C, D, E, F> PartialApply<A, B, C, D, E, F>(Func<A, B, C, D, E, F> f, A a) =>
            (B b, C c, D d, E e) => f(a, b, c, d, e);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<B, C, D, E, F, G> PartialApply<A, B, C, D, E, F, G>(Func<A, B, C, D, E, F, G> func, A a) =>
            (B b, C c, D d, E e, F f) => func(a, b, c, d, e, f);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<B, C, D, E, F, G, H> PartialApply<A, B, C, D, E, F, G, H>(Func<A, B, C, D, E, F, G, H> func, A a) =>
            (B b, C c, D d, E e, F f, G g) => func(a, b, c, d, e, f, g);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<A, Func<B, C>> Curry<A, B, C>(this Func<A, B, C> func) =>
            a => b => func(a, b);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<A, B, Func<C, D>> Curry<A, B, C, D>(this Func<A, B, C, D> func) =>
            (a, b) => c => func(a, b, c);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<A, B, C, Func<D, E>> Curry<A, B, C, D, E>(this Func<A, B, C, D, E> func) =>
            (a, b, c) => d => func(a, b, c, d);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<A, B, C, D, Func<E, F>> Curry<A, B, C, D, E, F>(this Func<A, B, C, D, E, F> func) =>
            (a, b, c, d) => e => func(a, b, c, d, e);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<A, B, C, D, E, Func<F, G>> Curry<A, B, C, D, E, F, G>(this Func<A, B, C, D, E, F, G> func) =>
            (a, b, c, d, e) => f => func(a, b, c, d, e, f);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Func<A, B, C, D, E, F, Func<G, H>> Curry<A, B, C, D, E, F, G, H>(this Func<A, B, C, D, E, F, G, H> func) =>
            (a, b, c, d, e, f) => g => func(a, b, c, d, e, f, g);
    }
}