Lambda the Ultimate

Extension Methods

a la SmallTalk

Instead of making a string class of your own, you can extend it without inheritance or composition. The method "Chomp" does not exist in .NET string type.

----------Extensions.cs-------------
namespace MyCompany.StringUtilities
{
	public static class Extensions
	{
		public static int Chomp(this string s) 
		{
			return s.EndsWith("\n") ? s.TrimEnd("\n".ToCharArray()) : s;
		}

	}

}

-------MyClass.cs------------
using MyCompany.StringUtilities;

class MyClass 
{
	public static void Main()
	{
		string s1 = "test\n";
	        string s2 = s1.Chomp();
	}
}

Lambda Expressions

As taken from the Language Specifications:

x => x + 1	// Implicitly typed, expression body
x => { return x + 1; }	// Implicitly typed, statement body
(int x) => x + 1	// Explicitly typed, expression body
(int x) => { return x + 1; }	// Explicitly typed, statement body
(x, y) => x * y		// Multiple parameters
() => Console.WriteLine()	// No parameters

myObject.MyMethodTakingDelegateParam( x => x + 1);

Type Inference

int i; // you can still use type annotations
var i = 0;  // type inferred as int
var name = "dude";  // type inferred as string;
var question = new[] { "dude", "where's", "my", "car" }; // type inferred string[] array

Anonymous Types

var person = new { Name = "dude", Weight = 150 }
var employees = new[] {
	new {
		Name = "Chris Smith",
		PhoneNumbers = new[] { "206-555-0101", "425-882-8080" }
	},
	new {
		Name = "Bob Harris",
		PhoneNumbers = new[] { "650-555-0199" }
	}
};

The actual mention on OSNews (titled "Nemerle 0.9.0 released") is getting harder to track down.

Falcon, if you don't include the "this" keyword, how can C# tell that you want MyCompany.StringUtilities.Extensions.Chomp() to be an extension method instead of a normal method in the Extensions class?

The "this" keyword is what signals to C# 3.0 that this is an extension method. This is logical since the string "s" becomes the hidden "this" parameter when calling Chomp().