Presentation was given june 2011 in sanko.net meeting

1. Functional programming and F# Sanko.net meeting 8.6.2011

2. Agenda Functional programming from c# perspective, Linq principles Functional programming in general F# and C# interoperability F# examples: ’basic’ stuff F# vs. C#

3. Agenda Functional programming from c# perspective, Linq principles Functional programming in general F# and C# interoperability F# examples: ’basic’ stuff F# vs. C# Eh? There’s a bug in the Agenda!!! Wrong order and names missing!

4. This happens, when you Powerpoint without test harness! Lets kick the PowerPoint and.... Correct the agenda using....

5. F#? This happens, when you Powerpoint without test harness! Lets kick the PowerPoint and.... Correct the agenda using....

6. F#? This happens, when you 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.fs And if you don’t have internet access, snapshotted source just for you module SlideDemo open System; type PresentationKeeper(name: string, employer : string) = member lollis.name = name member fuulis.employer = employer override this.ToString() = name + ", " + employer let 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, simply because its fun!

10. Why F#? Well, simply because its fun! (fun is reserved keyword, for expression)!

11. F# has / is: Succint Closures Functional Generics Discrimated unions .net official language (v4  ) Pattern matching Tail recursion optimization Tuples Immutable by default asynchronous workflows Very expressive Interoperable Type inference Classes Infinite lists etc. (laziness) Strongly typed Hybrid (oo, imperative) Lambda expressions (anon func) REPL (interactive) OCaml

12. F# has / is: But for now, lets focus on this! Functional

14. Functions as first class ”citizens”

15. Recursion

16. No mutable state Many other concepts apply, but these are ones to focus in this presentation

17. Immutability: Object cannot be changed after creation In C#, mark fields as readonly No mutable state  no local variables

19. Recursion: In functional programming, no iteration or ”looping” Recursion is very important concept

23. Time to switch to Visual Studio! (for good this time)