FuncExtensions

using System;

namespace FunctionalProgrammingInCSharp
{
    public static class FuncExtensions
    {
        public static Func<T1, Func<T2, TResult>> Curry<T1, T2, TResult>(this Func<T1, T2, TResult> func) =>
            x => y => func(x, y);

        public static Func<T2, TResult> Partial<T1, T2, TResult>(this Func<T1, T2, TResult> function, T1 arg1) =>
            b => function(arg1, b);

        public static Func<T2, T1, TResult> Flip<T1, T2, TResult>(this Func<T1, T2, TResult> function) =>
            (b, a) => function(a, b);

        public static Func<T1, TResult> FlipAndPartial<T1, T2, TResult>(this Func<T1, T2, TResult> func, T2 value) =>
            func.Flip().Partial(value);

        public static Func<T, TResult> Compose<T, TResult>(this Func<T, TResult> f, Func<T, T> g) where T : TResult =>
            x => f(g(x));

        public static Func<T, C, Func<T, C, R>, R> Compose<T, C, R>(this Func<T, C, Func<T, C, R>, R> outer, Func<T, C, Func<T, C, R>, R> inner)
        {
            return (target, token, next) => outer(target, token, (t, c) => inner(t, c, next));
        }

        public static Func<T> Aggregate<T>(this Func<T> action, Func<T, T> other)
        {
            T a = action();
            T b = other(a);
            return () => b;
        }
    }
}