F# and functional programming

F# and functional programming

• 1.
  Functional programming andF#Sanko.net meeting 8.6.2011
• 2.
  AgendaFunctional programming fromc# perspective, Linq principlesFunctional programming in generalF# and C# interoperabilityF# examples: ’basic’ stuffF# vs. C#
• 3.
  AgendaFunctional programming fromc# perspective, Linq principlesFunctional programming in generalF# and C# interoperabilityF# examples: ’basic’ stuffF# vs. C# Eh?There’s a bug in the Agenda!!!Wrong order and names missing!
• 4.
  This happens, whenyou Powerpoint without test harness! Lets kick the PowerPoint and.... Correct the agenda using....
• 5.
  F#?This happens, whenyou Powerpoint without test harness! Lets kick the PowerPoint and.... Correct the agenda using....
• 6.
  F#?This happens, whenyou Powerpoint without test harness! Lets kick the PowerPoint and.... Correct the agenda using....Java guy? Great!
• 7.
  Demo.... Source available@ github: https://github.com/ramik/Demo/blob/master/FunctionalTutorial/CSharpExamples/PresisDemo/SlideDemo.fsAnd if you don’t have internet access, snapshotted source just for youmodule SlideDemoopen System;type PresentationKeeper(name: string, employer : string) = member lollis.name = name member fuulis.employer = employer override this.ToString() = name + ", " + employerlet Rami = PresentationKeeper("Rami Karjalainen", "Reaktor")let Tuomas = PresentationKeeper("Tuomas Hietanen", "Basware")let topics = [ (2, "Functional programming from c# perspective, Linq principles", Tuomas); (1, "Functional programming in general", Rami); (3, "F# examples: ’basic’ stuff", Rami); (4, "F# and C# interoperability", Rami); (5, "F# vs. C#", Tuomas) ]let formatTopic topic keeper = String.Format ("{0} ({1})", topic, keeper.ToString())let pimpTheList = topics |> Seq.sortBy (fun (prio,_,_) -> prio) |> Seq.map (fun (_, a, b) -> a,b) |> Seq.map (fun x -> (formatTopic (fst x) (snd x)))let printPimped x = x |> Seq.iter (fun c -> printfn "%s" c)
• 8.
  Why F#?
• 9.
  Why F#?Well, simplybecause its fun!
• 10.
  Why F#?Well, simplybecause its fun!(fun is reserved keyword, for expression)!
• 11.
  F# has /is:SuccintClosuresFunctionalGenericsDiscrimated unions.net official language (v4  )Pattern matchingTail recursion optimization TuplesImmutable by defaultasynchronous workflowsVery expressiveInteroperableType inferenceClassesInfinite lists etc. (laziness) Strongly typedHybrid (oo, imperative)Lambda expressions (anon func)REPL (interactive)OCaml
• 12.
  F# has /is:But for now, lets focus on this!Functional
• 13.
  Well, what isfunctional programming?Immutable constructs
• 14.
  Functions as firstclass ”citizens”
• 15.
  Recursion
• 16.
  No mutable stateMany other concepts apply, but these are ones to focus in this presentation
• 17.
  Immutability:Object cannot bechanged after creationIn C#, mark fields as readonlyNo mutable state  no local variables
• 18.
  Functions as firstclass citizens:Functions can be passed as normal parameters CompositionHigher order functionsTakes a function as paramand/orReturns a function as outputFunctions as first class citizens:Functions can be passed as normal parameters CompositionHigher order functionsTakes a function as paramand/orReturns a function as outputTuomas will cover the deeps of the function theory later in the session
• 19.
  Recursion:In functional programming,no iteration or ”looping”Recursion is very important concept
• 20.
  Recursion:In functional programming,no iteration or ”looping”Recursion is very important conceptRecursion is very important, as without it ....
• 21.
  Recursion:In functional programming,no iteration or ”looping”Recursion is very important conceptRecursion is very important, as without it ....
• 22.
  Recursion:In functional programming,no iteration or ”looping”Recursion is very important conceptRecursion is very important, as without it ....Tail recursion or stack says bye!
• 23.
  Time to switchto Visual Studio!(for good this time)