Sum of tuples, pure functional

sum_tuples.cs

  public class MyTupleIntTest
  {
    [Fact]
    public void should_retain_values()
    {
      var tuple = MyTuple.Build(44, 100);

      tuple.First().Should().Be(44);
      tuple.Second().Should().Be(100);
    }

    [Fact]
    public void should_add_tuples()
    {
      var tuple1 = MyTuple.Build(2, 5);
      var tuple2 = MyTuple.Build(100, 50);

      var result = tuple1.Add(tuple2);

      result.First().Should().Be(102);
      result.Second().Should().Be(55);
    }
  }

  public static class MyTuple
  {
    public static Func<Func<int, int, int>, int> Build(int a, int b) => f => f(a, b);

    public static int First(this Func<Func<int, int, int>, int> tuple) => tuple((a, _) => a);
    
    public static int Second(this Func<Func<int, int, int>, int> tuple) => tuple((_, b) => b);
    
    public static Func<Func<int, int, int>, int> Add(
      this Func<Func<int, int, int>, int> a, 
      Func<Func<int, int, int>, int> b) => Build(a.First() + b.First(), a.Second() + b.Second());
}