using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace t1
{
    static class Program
    {

        static void Main(string[] args)
        {
            var v = new List<int>();
            for (var i = 0; i < 10; i++) v.Add(i);
            Console.WriteLine();
            var csum = Curry<int[], int, int>(Sum);
            var fix = Uncurry(IFix(csum));
            var r = fix(v.ToArray(), 0);
            Console.WriteLine(r);
            Console.ReadKey();
        }

        static int Sum(Func<int[], int, int> fix, int[] array, int index)
        {
            if (index >= array.Length) return 0;
            return fix(array, index + 1) + 1;
        }

        static Func<I, O> Fix<I, O>(Func<Func<I, O>, Func<I, O>> f)
        {
            //Y f = f ( Y f )
            return x => f(Fix(f))(x);
        }

        static Func<Func<Tuple<I1, I2>, O>, Func<Tuple<I1, I2>, O>> Curry<I1, I2, O>(Func<Func<I1, I2, O>, I1, I2, O> f)
        {
            return y => i => f(Uncurry(y), i.Item1, i.Item2);
        }

        static Func<I1, I2, O> Uncurry<I1, I2, O>(Func<Tuple<I1, I2>, O> f)
        {
            return (t1, t2) => f(Tuple.Create(t1, t2));
        }

        static Func<I, O> IFix<I, O>(Func<Func<I, O>, Func<I, O>> f)
        {
            return x =>
            {
                //f(Fix(f))(x);
                I got = default(I);
                var called = true;
                Func<I, O> next = i =>
                {
                    got = i;
                    called = true;
                    return default(O);
                };
                var ret = f(next)(x);
                while (called)
                {
                    called = false;
                    ret = f(next)(got);
                }
                return default(O);
            };
        }

    }
}