F #: Hello, World

About a year later, we are waiting for the next release of Microsoft Visual Studio and perhaps the most delicious new product promises to be F # - a functional language through the eyes of young people from the Cambridge Microsoft Research laboratory. This language is completely new and is now at the licking stage in the Microsoft Research laboratories. Microsoft is positioning F # as one of the main languages ​​for .Net along with C # and VB.Net, which most likely means that sooner or later, many programmers will have to deal with .Net. I, like many developers, have never come across purely functional languages, but the principle “Prepare sledge in summer” has not yet been canceled. This article is my personal little "Hello F #".

So, you can feel the novelty now. For this we need Visual Studio 2008 and Microsoft F #, September 2008 Community Technology Preview . After installing the latter, a new project branch will appear in the studio - Visual F #.
Let's create a console application and after some time spent on google, we will try to say hello to the world:

// - <br/>
#light <br/>

// C# : using System; <br/>
open System<br/>

// <br/>
printfn "Hello, World! What is your name, user?" <br/>

// ? C# : var name = Console.ReadLine(); <br/>
let name = Console .ReadLine()<br/>

// , "" who. <br/>
// C#: <br/>
// public delegate void SaySomethingDelegate(string toWho); <br/>
// SaySomethingDelegate sayHello = who => Console.WriteLine("Hello, {0}!", who); <br/>
let sayHello who = printfn "Hello, %s!" who<br/>

// , ! <br/>
sayHello name<br/>

// .Net Framework: <br/>
let sayHelloDotNet who = Console .WriteLine( "Hello from F# via .Net, " + name + "!" )<br/>

// ! <br/>
sayHelloDotNet name<br/>

// :) <br/>
let rec fib i = // <br/>
match i with // <br/>
| 1 | 2 -> 1 // 1 2, 1 <br/>
| i -> fib(i-1) + fib(i-2) // - <br/>

// , <br/>
printfn "%i" (fib 20)<br/>

* This source code was highlighted with Source Code Highlighter .

Output of our program:

Hello, World! What is your name, user?
Habrahabr
Hello, Habrahabr!
Hello from F# via .Net, Habrahabr!
6765


Like this. The language is quite pleasant. Yes, OP is a fundamentally different area than traditional languages ​​like C #. Yes, F # is still raw. Yes, many features are missing. Yes, there is Nemerle , but it is unlikely that MS will drastically change F # over the coming year.
If there is interest in this topic - I will try to write something else, at least this area is very interesting to me.