Where to practice Lambda function? [closed]

Question

I am currently trying to learn all new features of C#3.0. I have found a very nice collection of sample to practice LINQ but I can't find something similar for Lambda.

Do you have a place that I could practice Lambda function?

Update

LINQpad is great to learn Linq (thx for the one who suggest) and use a little bit Lambda in some expression. But I would be interesting in more specific exercise for Lambda.

Answer 1

LINQPad is a good tool for learning LINQ

Answer 2

Lambdas are just something that, once you get your head around, you "get" it. If you're using a delegate currently, you can replace it with a lambda. Also the System.Action<...>, System.Func<...>, and System.Predicate<...> additions are nice shortcuts. Some examples showing syntax would be helpful though (warning: they are inane but I wanted to illustrate how you can swap functions):

public static void Main()
{
    // ToString is shown below for clarification
    Func<int,string,string> intAndString = (x, y) => x.ToString() + y.ToString();
    Func<bool, float, string> boolAndFloat = (x, y) => x.ToString() + y.ToString();

    // with declared
    Combine(13, "dog", intAndString);
    Combine(true, 37.893f, boolAndFloat);

    // inline
    Combine("a string", " with another", (s1, s2) => s1 + s2);
    // and multiline - note inclusion of return
    Combine(new[] { 1, 2, 3 }, new[] { 6, 7, 8 },
        (arr1, arr2) =>
        {
            var ret = "";
            foreach (var i in arr1)
            {
                ret += i.ToString();
            }
            foreach (var n in arr2)
            {
                ret += n.ToString();
            }

            return ret;
        }
    );

    // addition
    PerformOperation(2, 2, (x, y) => 2 + 2);
    // sum, multi-line
    PerformOperation(new[] { 1, 2, 3 }, new[] { 12, 13, 14 },
        (arr1, arr2) =>
        {
            var ret = 0;
            foreach (var i in arr1)
                ret += i;
            foreach (var i in arr2)
                ret += i;
            return ret;
        }
    );

    Console.ReadLine();

}

public static void Combine<TOne, TTwo>(TOne one, TTwo two, Func<TOne, TTwo, string> vd)
{
    Console.WriteLine("Appended: " + vd(one, two));
}

public static void PerformOperation<T,TResult>(T one, T two, Func<T, T, TResult> func)
{
    Console.WriteLine("{0} operation {1} is {2}.", one, two, func(one,two));
}

Mostly what confused me was the shortcut syntax, for example when using System.Action to just execute a delegate with no parameters you could use:

var a = new Action(() => Console.WriteLine("Yay!"));

Or you could do:

Action a = () => Console.WriteLine("Yay");

When you've got an Action, Func, or Predicate that takes one argument you can omit the parenthesis:

var f = new Func<int, bool>(anInt => anInt > 0);

or:

// note: no var here, explicit declaration
Func<int,bool> f = anInt => anInt > 0;

instead of:

Func<int,bool> f = (anInt) => anInt > 0;

or to go to the extreme:

Func<int,bool> f = (anInt) =>
{
    return anInt > 0;
}

As shown above, single line lambdas do not require the return statement, though multiline Func lambdas do.

I think you will find the best way to learn how to use lambdas is to work a lot with collections and include System.Linq in your using namespaces - you will see a ton of extension methods for your collections and most of these methods allow you to exercise your knowledge of lambdas.