F# on the Road to Visual Studio 2010

With thanks to Don Syme, Leon “secretGeek” Bambrick, Chris Smith

and the puppies

Robert Pickering – LexiFi (ALTi)

Session Overview

• Why was F# created? Why learn F#?

• A taste of the F# language– Especially the functional side!

• See a complete working F# “Collective Intelligence” application

F#...

Do not be afraid.

Part 1

hello

I’m F#

Friendly, Approachable.

I'll let you in on a secret: I'm doing F# simply because it's lots and lots of fun. In a very broad sense of the word: functional programming is fun, OO programming with F# is fun, watching people use F# is fun.

One of the wonderful things about F# is that you can actually end up working in your domain. In the zone. With F#, you're not necessarily "just" a programmer! You're likely to also be a probabilistic modeller, or an AutoCAD engineer, or a finance engineer, or a symbolic programmer, or one of many other things.

- Don Syme, F#’s creator

F# is unique amongst both imperative and declarative languages in that it is the golden middle road where these two extremes converge. F# takes the best features of both paradigms and tastefully combines them in a highly productive and elegant language that both scientists and developers identify with. F# makes programmers better mathematicians and mathematicians better programmers.

- Eric Meijer, Forward to Expert F#

Julien LaugelHead of Research & DevelopmentEuroPerformance

A Few Words From …

F#: Combining ParadigmsI've been coding in F# lately, for a production task.

F# allows you to move smoothly in your programming style... I start with pure functional code, shift slightly towards an object-oriented style, and in production code, I sometimes have to do some imperative programming.

I can start with a pure idea, and still finish my project with realistic code. You're never disappointed in any phase of the project!

Julien Laugel, Head of Research & Development, EuroPerformance

F#: Influences

OCa

ml

C#/.NETF#

Similar core language

Similar objectmodel

• Current Release: September CTP for VS 2008

• Next Release: as part of VS 2010 beta 1

• Plugin for VS Shell and CodePlex release in VS 2010 timeframe

• More:http://blogs.msdn.com/dsyme/archive/2008/12/10/fsharp-to-ship-as-part-of-visual-studio-2010.aspx

Road Map

Part 2

F# the Language ...

... and the Functional Point of View

Code!//F#open Systemlet a = 2Console.WriteLine a

//C#using System;

namespace ConsoleApplication1{ class Program { static int a() { return 2; } static void Main(string[] args) { Console.WriteLine(a); } }}

More Code!//F#open Systemlet a = 2Console.WriteLine a

//C#using System;

namespace ConsoleApplication1{ class Program { static nt a() { return 2; }

static void Main(string[] args) { Console.WriteLine(a); } }}

More Noise Than Signal!

Let Bindings & Literals

let aString = "Stringy" // a string

Declaration of a binding

Like “var” in C#

An identifier

A literal

A comment

ListsLet binding

The empty list

The empty list

ConcatenateLiteral

// the empty listlet emptyList = []

// adding to a listlet conact = "One" :: []

Lists

let list = 1 :: 2 :: 3 :: []

let list = [1; 2; 3]

These are the same

// a functionlet addTen = fun x -> x + 10

Functions

Let binding

Parameter

Result

Functions

Let binding

Parameter

Result

// shorter versionlet addTen x = x + 10

FunctionsLet binding

Result

Parameters

WhitespaceSensitive

IntermediateValue

// multi parameters and // intermediate resultslet addThenTimesTwo x y = let temp = x + y temp * 2

Pattern Matching

// simple pattern matchinglet matching n = match n with | 1 -> "One" | 2 -> "Two" | _ -> "Other"

Pattern Result

Pattern Matching

// more pattern matching// over listslet rec subOne list = match list with | head :: tail -> head - 1 :: subOne tail | [] -> []

Pattern

Result

Recursive function

Recursive call

// pattern matching// over listslet rec addOne list = match list with | head :: tail -> head + 1 :: addOne tail | [] -> []

DRY!

DRY

(ML is 23 years older than Ruby)

on’teapt

ourself

Functions as Parameters// pattern matching// over listslet rec map func list = match list with | head :: tail -> func head :: map tail | [] -> []

let addOne list = List.map (fun x -> x + 1) list

let subOne list = List.map (fun x -> x + 1) list

Function parameter

Call function

Part 3

A “Collective Intelligence” Example Application

Classifying the Bloggers

Representing a Blog

• A blog can be represented by the frequency that words appear in it

• Most and least common words are cut – words like “the” are ignored– words like “woah” are ignored

Phone Email Book People Affiliate

Heckler Spray 0 0 1 2 0

Shiny Shiny 3 0 0 5 0

Chris Garret on New Media 1 75 12 60 24

Measuring “Closeness” of Blogs

Email Book

People

Heckler Spray

Chris Garret on New Media

Measuring “Closeness” of Blogs

• Pervious slide shows “Euclidean Distance”• While this could be use we use “Pearson

correlation”– “Pearson correlation” corrects for the problem

that some blogs are longer than others

where

Pearson correlation in F#let pearson (wc1: seq<float>) (wc2: seq<float>) = let sum = PSeq.reduce (+) let sum1 = sum wc1 let sum2 = sum wc2 let sumSq1 = sum (Seq.map (fun x -> x * x) wc1) let sumSq2 = sum (Seq.map (fun x -> x * x) wc2) let pSum = sum (Seq.map2 (fun x y -> x * y) wc1 wc2) let len = float (Seq.length wc1) let num = pSum - ((sum1 * sum2) / len) let den = sqrt ((sumSq1 - (sum1 * sum1) / len) * (sumSq2 - (sum2 * sum2) / len)) if den = 0. then 0. else num / den

Hierarchical Clustering

A B

C

D E

A B

C

D E

A B

C

D E

B

E

C

A B

C

D E

A

D

Viewing the Hierarchical Clustering

A

B

C

D

E

THE ALGORITHMHow we implement hierarchical clustering efficiently in F#

Map

Fetch Data Process Data Build Tree

EndStart

Make HTTP Request

Clean DataSplit DataCount WordCreate Master Word List

Calculate Words UsedBuild Tree

Reduce

Map

Fetch Data Process Data Build Tree

EndStart

Reduce

Parallelized by Asynchronous WorkflowsParallelized by the Parallel Task Library

3 Layer Architecture

Data Access – dataAccess.fs

Business Logic – algo.fs

UI – Program.fs

Helpersextentions.fs

Tests – test.fsx

DEMOHierarchical clustering application in action

Application Metrics

• Helper/Extension Code: ~60 lines

• Data Access Code: ~30 lines

• Main algorithm: ~220 lines

• UI code: ~150 lines (F#) / ~40 lines (XAML)

Other Things To Cluster

• Any other kind of text:– Books from project Gutenberg– Twitter!– Messages boards or other web pages

• People in social networks

• Reviewers on Amazon

• Companies based on metrics

Collective IntelligenceBy Toby Segaran

Part 3

End Bit

msdn.microsoft.com/fsharp/

F# Resources• MDSN Resource center: http://msdn.microsoft.com/fsharp/

• User forums: http://cs.hubfs.net/forums

• Blogs (there are lots of others!): • http://blogs.msnd.com/dsyme• http://strangelights.com/blog

• Samples on the web:• http://code.msdn.microsoft.com/fsharpsamples • http://code.google.com/hosting/search?q=label:fsharp• http://codeplex.com/Project/ProjectDirectory.aspx?TagName=F%23

• Source available with the distribution: %ProgramFiles%\FSharp-1.9.6.2\source

Current Books about F#

Books to come about F#

Second Edition

alt.net.france

Program:• 18 February: Aspectize – Frédéric Fadel –

Winwise, 16 rue Gaillon 75002 Paris• 18 March: TDD – Djamel Zouaoui – chez OCTO

Technology, 50 avenue des champs Elysées• 22 April: Entity Framework – Matthieu MEZIL• More info: http://

groups.google.com/group/parisaltnet

Questions?