C# solution to g()(“al”)

Here is a fun coding problem. The idea is simple. g()(“al”) outputs “goal”. g()()(“al”) outputs “gooal”. And so on. So here is what it comes down to. A call to g(), needs to return either a function, or a string. Sounds simple enough. In C# you can get it done with heavy use of the ‘dynamic’ type, and a delegate.

namespace Goal
{
    using System;
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(G()("al"));
            Console.WriteLine(G()()("al"));
            Console.WriteLine(G()()()("al"));
            Console.WriteLine(G()()()()("al"));
            Console.WriteLine(G()()()()()("al"));
            Console.ReadLine();
        }
        delegate dynamic g(string a = "o");
        static dynamic G(string o = "o", string curr = "g")
        {
            return o == "al" ? (dynamic)curr + o : new g((a) => G(a, curr + o));
        }
    }
}

There we have it! The output will be something like:

• goal
• gooal
• goooal
• gooooal
• goooooal