Clousers

Albahari_Example.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Net;

internal class Program
{
    public static void Main()
    {
        var mem = MemoizeFunction<string, string>(GetWebPage);

        Stopwatch stopwatch = new();

        stopwatch.Start();
        var result = mem("https://www.youtube.com/");
        stopwatch.Stop();
        Console.WriteLine($"First result length: {result.Length} | time: {stopwatch.ElapsedMilliseconds}");
        stopwatch.Reset();

        stopwatch.Start();
        var result2 = mem("https://www.youtube.com/");
        stopwatch.Stop();
        Console.WriteLine($"Second result length: {result2.Length} | time: {stopwatch.ElapsedMilliseconds}");
        stopwatch.Reset();

        stopwatch.Start();
        var result3 = mem("https://www.youtube.com/");
        stopwatch.Stop();
        Console.WriteLine($"Third result length: {result3.Length} | time: {stopwatch.ElapsedMilliseconds}");
        stopwatch.Reset();
    }

    static Func<TIn, TOut> MemoizeFunction<TIn, TOut>(Func<TIn, TOut> func)
    {
        var cache = new Dictionary<TIn, TOut>();

        return input => cache.TryGetValue(input, out var result)
            ? result
            : cache[input] = func(input);
    }

    static string GetWebPage(string uri)
    {
        return new WebClient().DownloadString(uri);
    }
}