The document compares the Swift programming language to an unknown language X, describing various features and capabilities. It poses questions about language X that hint it is focused on cross-platform development, open source, safety, and functional programming. It is eventually revealed that language X is F#, and provides links to learn more about F# and its use for both front-end and back-end development across platforms like iOS, Android, and Azure.

1. vs.
?
Swift
Language X
Can you guess what language this is?

2. vs.
?
Native development for
one mobile platform
Native development for
three mobile platforms

3. vs.
?
Desktop apps for one OS
Desktop apps for three OSes

4. vs.
?
Client only development
Use the same language
on client and server
Cloud-ready too

5. vs.
?
Closed source
Open source

6. vs.
?
Well-designed language
Modern.
Designed for safety.
Concise yet expressive syntax.
Interactive and fun.
Fast and powerful.
Well-designed language
Modern.
Designed for safety.
Concise yet expressive syntax.
Interactive and fun.
Fast and powerful.

7. vs.
?
A low-risk switch
Benefits from an existing eco-system.
Can interop with legacy code.
Can access a large number of existing
libraries.
A low-risk switch
Benefits from an existing eco-system.
Can interop with legacy code.
Can access a large number of existing
libraries.

8. vs.
?
Many awesome language features
Type inference ∙ Optional types ∙ Interactive REPL
Pattern matching ∙ 1st class functions ∙ Concise syntax
Functional patterns ∙ Tuples ∙ Immutable data
Object orientation ∙ Operator overloading ∙ Closures
Many awesome language features
Type inference ∙ Optional types ∙ Interactive REPL
Pattern matching ∙ 1st class functions ∙ Concise syntax
Functional patterns ∙ Tuples ∙ Immutable data
Object orientation ∙ Operator overloading ∙ Closures
And no semicolons!
And no semicolons!

9. vs.
?
Missing important things
Lacks full type inference ∙ No asynchronous flow
No parallelism ∙ Tricky garbage collection
Important things included
Excellent type inference ∙ Built-in async flow
Parallelism ∙ Algebraic types ∙ Units of measure
More powerful pattern matching ∙ Agents
One line parsing of JSON, XML, CSV
Syntax support for database queries.
Also, a very young language
And a mature language

10. ? So what is language X?

11. ? So what is language X?
Language X is F#

12. ? So what is language X?
Language X is F#
Surprised?
Why don't you give F# a try and see for
yourself?
What do other people say?
http://fsharp.org/testimonials/

13. Try F#
The F# Software Foundation has links to
everything you need: http://fsharp.org/
Learn key principles in just a few minutes:
http://www.tryfsharp.org/Learn
Play with it in a browser:
http://www.tryfsharp.org/Create
https://dotnetfiddle.net/

14. F# is available "out of the box" on all Xamarin-
supported platforms: Android, OS X and iOS.
http://developer.xamarin.com/guides/cross-
platform/fsharp/
Build better apps for iOS, Android and Mac with Xamarin
Studio: http://xamarin.com/studio
Or build native iOS, Android and Windows
apps in Visual Studio: http://xamarin.com/visual-studio
MonoGame on iOS: http://neildanson.wordpress.com/2013/07/31/f-and-
monogame-part-3-ios/
F# on the front end

15. 10 Reasons Why F# is a Hot Programming
Language for Developers: http://bit.ly/10-
reasons-why
Web Programming with F#: http://fsharp.org/webstacks/
F# on Azure: http://fsharp.org/cloud/
F# for data science: http://fsharp.org/data-science/
... and much more at http://fsharp.org/
F# on the back end