On my flight to the US I had a small competition with my dad. He was solving a Sudoku and I tried to write a generic solver in the same time. I admit he was a little bit faster but anyway I put my code on github.
Tags: F#, SudokuOn my flight to the US I had a small competition with my dad. He was solving a Sudoku and I tried to write a generic solver in the same time. I admit he was a little bit faster but anyway I put my code on github.
Tags: F#, Sudoku![]() |
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Letzte Woche habe ich im Rahmen der F# Gruppe der .NET Online User Group einen Vortrag zu “Higher-Order-Functions in C#†gehalten. Unter http://vimeo.com/17048170 ist die Aufzeichnung nun zu finden.
Tags: .NET Online User Group, F#Funktionale Programmiersprachen nehmen seit geraumer Zeit einen hohen Stellenwert in der Wissenschaft ein. Mittlerweile ziehen viele der funktionalen Konzepte bereits in den Mainstream ein. Bei diesem Treffen wollen wir einen Einblick in funktionale Konzepte und deren Umsetzung in C# gewinnen. Insbesondere soll auf "Funktionen höherer Ordnung", "Pattern Matching", "Unveränderlichkeit" und parallele Programmierung eingegangen werden.
Vortragsabstract
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Gestern hat Björn Rochel mit seinem Vortrag zum Thema Rhino.ServiceBus den aktiven Start der .NET Online User Group vollzogen. Mit 28 Teilnehmern war dies (trotz einiger technischer Probleme bei mir als geplantem Co-Moderator) schon ein voller Erfolg. Wenn die nächsten Treffen auch so in der Art stattfinden, dann kann die NOUG (Twitter-Hashtag #NOUG) echt etwas Großes werden. Danke an alle die mitmachen und der NOUG in so kurzer Zeit schon ein Gesicht und Struktur geben.
Björn hat aus seinem Vortrag auch schon eine geniale weiterführende Idee für die NOUG entwickelt. In einer "Build your own CQRS"-Gruppe will er gemeinsam mit anderen Interessierten eine vollständige Implementierung einer CQRS – Beispielanwendung vorantreiben.
Nächsten Montag hat dann die F#-Gruppe ihr Kick-Off-Meeting. Ich würde mich über viele interessierte Teilnehmer freuen. Bei diesem Treffen wollen wir einen ersten Einblick in funktionale Konzepte gewinnen. Insbesondere soll auf "Funktionen höherer Ordnung", "Pattern Matching", "Unveränderlichkeit" und parallele Programmierung eingegangen werden. Damit wir uns nicht zu sehr in Diskussionen zur F#-Syntax verfangen wollen wir dies beim ersten Treffen in C# probieren. Damit wir auch ein möglichst interaktives Treffen hinbekommen wäre ein Mikrofon und im Idealfall auch eine Webcam nicht schlecht. 😉
Wichtige Links:
[Das Bild habe ich schamlos von DerAlbert geklaut.]
Tags: .NET Online User Group, CQRS, F#, Rhino.ServiceBus![]() |
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Nach einigen Diskussionen und Anregungen auf Twitter und einer konstitutionellen Skype-Session (zwischen DerAlbert, Björn Rochel und mir) wurde heute die “.NET Online User Group†gegründet.
Unter dem Deckmantel dieser Gruppe wollen wir versuchen möglichst oft und regelmäßig Online-Treffen für .NET-Entwickler aus dem deutschsprachigen Raum zu organisieren.
Die Online User Group sieht sich damit keinesfalls als Konkurrenz zu den bereits bestehenden lokalen User Groups. Wir stellen uns dabei eher vor durch ein breites Angebot an Formaten und das große Einzugsgebiet auch in speziellere Themen tief reinschauen zu können, die bei den lokalen Gruppen aufgrund der heterogenen Interessen eher vermieden werden.
So ist es z.B. geplant Gruppen zu bilden, die sich zu bestimmten “Randgruppenâ€-Themen ganz intensiv austauschen können. Den Anfang machen wir mit einer F# Gruppe, deren Ziel es ist die Sprache F# im Speziellen und Funktionale Programmierung im Allgemeinen detailliert zu beleuchten. Beim ersten Treffen am 15.11. wollen wir uns mit “Funktionen höherer Ordnung†beschäftigen.
Jede der Gruppen wird min. einen Paten haben. Die Aufgabe des Paten ist es als Ansprechpartner zu fungieren und Termine zu koordinieren. Das soll aber nicht heißen, dass der Pate bei jedem Treffen selbst einen Vortrag halten soll.
In letzter Zeit ist es des Öfteren vorgekommen, dass einige Themen auf Twitter oder in Newsgroups plötzlich sehr intensiv diskutiert wurden. Wir wollen mit der User Group nun auch eine Kommunikationsplattform bieten, die in der Lage ist kurzfristig in einem direkteren Rahmen über solche Themen zu diskutieren. Wir können uns dabei gut vorstellen, dass spontan verabredet wird (z.B. über Twitter) sich am Abend zu einem bestimmten Thema über die Kanäle der User Group (insbesondere LiveMeeting) zu unterhalten.
Auch das bereits etablierte Online Coding Dojo mit Albert Weinert und Ilker Cetinkaya wird ab jetzt unter der Flagge der .NET Online User Group durchgeführt werden. Der erste Termin hierfür ist der 18. November.
Aber auch Vorträge wird es bei der .NET Online User Group geben. Zum jetzigen Zeitpunkt stehen bereits 4 Termine fest:
Um die .NET Online User Group ordentlich anlaufen lassen zu können benötigen wir natürlich jede Menge Hilfe:
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This article has been moved to http://fsharp.github.io/FAKE/specifictargets.html
Tags: F#, F-sharp Make, Fake![]() |
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Today I released a new bugfix release for “FAKE – F# Makeâ€. We fixed some path and logging issues and as a new feature we introduced the @@ operator which allows to combine paths.
Tags: F#, F#, F-sharp Make![]() |
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Yesterday I showed how we can map some of the Rx operators to an API which looks more like the F# base classes. Today I wanted to use these mapped operators in a WPF-application written in F#.
F# gives us a nice way to use events as first class citizen (via IEvent) but these events implement their own version of IObservable<T> (in FSharp.Core.dll), which is unfortunately incompatible with the Rx version and therefore with the mapped API.
The solution I found is to wrap the F# IEvent with a Rx IObservable<T>:
/// Generates an observable from an IEvent
let fromEvent (event:IEvent<_,_>) =
Observable.Create<_>(fun x ->
event.Subscribe x.OnNext |> ignore
new System.Action(fun () -> ()))
Now we are able to use the WPF events as observables:
// Register ListBox Commands
listBox1.KeyDown
|> Observable.fromEvent
|> Observable.filter (fun args -> args.Key = Key.Delete)
|> Observable.subscribe deleteElement
I am interested if someone has a different and maybe better solution to this problem.
Updated: 21.12.2009 – Observable.Context is no longer supported by Rx ==> Removed
Tags: F#, Reactive Framework![]() |
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The “Reactive Extensions for .NET (Rx)†comes with lot’s of operators for using IObservable<T>. This code mimics the signature of the default F# sequence combinators and allows to use observables like sequences. It is a similar approach like Matthews Podwysocki’s blog post about mapping the IParallelEnumerable.
I will update this post from time to time to include more of the operators.
module RxExtensions.Observable
open System.Linq
open System
open System.Threading
open System.Windows.Threading
type ‘a observable = IObservable<‘a>
type ‘a observer = IObserver<‘a>
/// converts a lambda in a System.Action
let asAction f = new System.Action(f)
/// System.Action whichs does nothing
let doNothing = asAction (fun () -> ())
/// Creates an observer
let createObserver next error completed =
{new System.IObserver<_> with
member this.OnCompleted() = completed()
member this.OnError(e) = error e
member this.OnNext(args) = next args}
/// Creates a new observable
let create f =
Observable.Create<_>(fun x ->
f x
doNothing)
/// Creates a observable from a async
let ofAsync async =
create
(fun obs ->
Async.StartWithContinuations
(async,obs.OnNext,obs.OnError,obs.OnError))
/// Gets a dispatcher Schdeuler for the current dispatcher
let getDispatcherScheduler _ =
new DispatcherScheduler(Dispatcher.CurrentDispatcher)
/// Generates an observable from an IEvent
let fromEvent (event:IEvent<_,_>) = create (fun x -> event.Add x.OnNext)
/// Generates an empty observable
let empty<‘a> = Observable.Empty<‘a>()
/// Takes the head of the elements
let head = Observable.First
/// Merges the two observables
let mergeWith obs1 obs2 = Observable.Merge(obs2, obs1)
/// Merges all observables
let mergeAll (observables:IObservable<IObservable<‘a>>) =
Observable.Merge observables
/// Merges all observables
let merge (observables:(IObservable<‘a>) seq) =
Observable.Merge observables
/// Creates a range as an observable
let range start count = Observable.Range(start, count)
/// Converts a seq in an observable
let toObservable (seq: ‘a seq) = Observable.ToObservable seq
/// Converts a observable in a seq
let toEnumerable = Observable.ToEnumerable
/// Subscribes to the Observable with all 3 callbacks
let subscribeComplete next error completed (observable: ‘a observable) =
observable.Subscribe(
(fun x -> next x),
(fun e -> error e),
(fun () -> completed()))
/// Subscribes to the Observable with a
/// next and an error-function
let subscribeWithError next error observable =
subscribeComplete next error (fun () -> ()) observable
/// Subscribes to the Observable with just a next-function
let subscribe next observable =
subscribeWithError next ignore observable
/// throttles the observable for the given interval
let throttle interval observable =
Observable.Throttle(observable,interval)
/// throttles the observable scheduled on the current dispatcher
let throttleOnCurrentDispatcher interval observable =
Observable.Throttle(
observable,getDispatcherScheduler(),interval)
/// samples the observable at the given interval
let sample interval observable =
Observable.Sample(observable,interval)
/// samples the observable at the given interval
/// scheduled on the current dispatcher
let sampleOnCurrentDispatcher interval observable =
Observable.Sample(
observable,getDispatcherScheduler(),interval)
/// returns the observable sequence that reacts first.
let takeFirstOf2Reactions obs1 obs2 =
Observable.Amb(obs1,obs2)
/// returns the observable sequence that reacts first.
let amb (obs: IObservable<‘a> seq) =
Observable.Amb obs
/// returns the observable sequence that reacts first.
let takeFirstReaction (obs: IObservable<‘a> seq) =
Observable.Amb obs
/// Matches when both observable sequences
/// have an available value.
let both obs1 obs2 = Observable.And(obs1,obs2)
/// Merges two observable sequences
/// into one observable sequence.
let zip obs1 obs2 =
Observable.Zip(obs1, obs2, Func<_,_,_>(fun a b -> a, b))
/// Merges two observable sequences into one observable sequence
/// whenever one of the observable sequences has a new value.
/// ==> More results than zip
let combineLatest obs1 obs2 =
Observable.CombineLatest(
obs1, obs2, Func<_,_,_>(fun a b -> a, b))
/// Concats the two observables to one observable
let concat observable =
Observable.SelectMany(
observable,
Func<_,_>(fun (x:IObservable<‘a>) -> x))
/// maps the given observable with the given function
let map f observable =
Observable.Select(observable,Func<_,_>(f))
/// maps the given observable with the given function
let mapi f observable =
Observable.Select(observable,Func<_,_,_>(fun x i ->f i x))
/// Filters all elements where the given predicate is satified
let filter f observable =
Observable.Where(observable, Func<_,_>(f))
/// Splits the observable into two observables
/// Containing the elements for which the predicate returns
/// true and false respectively
let partition predicate observable =
filter predicate observable,
filter (predicate >> not) observable
/// Skips n elements
let skip n observable = Observable.Skip(observable, n)
/// Skips elements while the predicate is satisfied
let skipWhile f observable =
Observable.SkipWhile(observable, Func<_,_>(f))
/// Runs all observable sequences in parallel
/// and combines their first values.
let forkJoin (observables: (‘a observable) seq) =
Observable.ForkJoin observables
/// Counts the elements
let length = Observable.Count
/// Takes n elements
let take n observable =
Observable.Take(observable, n)
/// Determines whether the given observable is empty
let isEmpty observable = Observable.IsEmpty observable
/// Determines whether the given observable is not empty
let isNotEmpty observable = not (Observable.IsEmpty observable)
/// Determines whether an observable sequence
/// contains a specified value
/// which satisfies the given predicate
let exists predicate observable =
observable
|> skipWhile (predicate >> not)
|> isNotEmpty
/// Continues an observable sequence that is terminated
/// by an exception with the next observable sequence.
let catch (newObservable:IObservable<‘a>) failingObservable =
Observable.Catch(failingObservable,newObservable)
/// Takes elements while the predicate is satisfied
let takeWhile f observable =
Observable.TakeWhile(observable, Func<_,_>(f))
/// Iterates through the observable
/// and performs the given side-effect
let perform f observable =
Observable.Do(observable,fun x -> f x)
/// Invokes finallyAction after source observable
/// sequence terminates normally or by an exception.
let performFinally f observable =
Observable.Finally(observable,fun _ -> f())
/// Folds the observable
let fold f seed observable =
Observable.Aggregate(observable, seed, Func<_,_,_>(f))
/// Retruns an observable from a async pattern
let fromAsync beginF endF =
Observable.FromAsyncPattern<_>(
Func<_,_,_>(fun x y -> beginF(x,y)),
(fun x -> endF x)).Invoke()
/// Runs all observable sequences in parallel
/// and combines their first values.
let subscribeAll next observables =
observables |> Seq.map (subscribe next) |> Seq.toList
type IObservable<‘a> with
/// Subscribes to the Observable with just a next-function
member this.Subscribe(next) =
subscribe next this
/// Subscribes to the Observable with a next
/// and an error-function
member this.Subscribe(next,error) =
subscribeWithError next error this
/// Subscribes to the Observable with all 3 callbacks
member this.Subscribe(next,error,completed) =
subscribeComplete next error completed this
open System.Net
type WebRequest with
member this.GetRequestStreamAsync() =
fromAsync
this.BeginGetRequestStream
this.EndGetRequestStream
member this.GetResponseAsync() =
fromAsync
this.BeginGetResponse
this.EndGetResponse
member this.GetResponseStreamAsync() =
fromAsync
this.BeginGetRequestStream
this.EndGetRequestStream
type Async<‘a> with
member this.ToObservable() = ofAsync this
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I just released a new version of my Open Source Build Automation Framework “FAKE – F# Makeâ€. You can read more about FAKE on the project website or in the Getting started with "FAKE – F# Make"-article.
Although the new release contains many bugfixes, I only want to show the two major improvements here.
From now on FAKE uses the “F# Interactive†(fsi.exe) instead of the F# Compiler (fsc.exe) to run the build scripts, which brings two major improvements.
Due to the fact that FAKE scripts are no longer compiled at the beginning of the build process, we don’t need a temporary folder for the created binaries.
The #load command in F# scripts allows us to load modules at runtime. Now we are able to put reusable Targets or TargetTemplates (see below) into external build script files.
TargetTemplates provide an easy way to reuse common Targets. Let’s consider a (very) small sample:
Target "TraceHello" (fun () ->
trace "Hello World from FAKE"
)
This Target “TraceHello†traces a “Hello World†string into our build log. Now we want it to be slightly more generic and to trace a custom string. We can do this by using a TargetTemplate:
/// createTraceTarget: string -> string -> Target
let createTraceTarget = TargetTemplate (fun s ->
trace s
)
Now we have a template (or a function which generates targets) that gets a string for the target name and a string for the trace text and generates a usable target:
createTraceTarget "TraceHello" "Hello World from FAKE"
createTraceTarget "Trace2" "Trace another text"
Of course the TargetTemplate function is generic and can be used with any tuple as parameter:
/// createTraceTarget: string -> string*int -> Target
let createTraceTarget = TargetTemplate (fun (s,d) ->
trace s
trace <| sprintf "my int: %d" d
)
createTraceTarget "TraceHello" ("Hello World from FAKE",2)
createTraceTarget "Trace2" ("Trace another text",42)
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This artile has been moved to http://fsharp.github.io/FAKE/teamcity.html
Tags: Code Quality, Continuous Integration, F#, F-sharp Make, Fake, FxCop, nunit, TeamCity![]() |
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