Category.cs

using System;

public static class Category {
  public static T Identity<T>(T obj) {
    return obj;
  }
  
  public static Func<T1, TFinal> Compose<T1, TResult, TFinal>(Func<TResult, TFinal> f, Func<T1, TResult> g) {
    return (T1 t) => {
      return f(g(t));
    };
  }
}