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CSharp · Console

/Program.cs

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

public class Program
{
    public static async Task Main()
    {
        Console.WriteLine(await FutureApplicative.LiftA2(Task.FromResult(10), FutureApplicative.Pure(20), (a, b) => a*b)); // выведет 200
    }
}

public static class FutureApplicative
{
    public static Task<A> Pure<A>(A a) => Task.FromResult(a);

    public static async Task<C> LiftA2<A, B, C>(Task<A> ta, Task<B> tb, Func<A, B, C> map2)
    {
        await Task.WhenAll(ta, tb);
        return map2(ta.Result, tb.Result);
    }
}