Introduction to the F# language for curious C# developers

1. F# Eye 4 the C# Guy
Phillip Trelford
@ptrelford
http://trelford.com/blog

2. Visual F#

3. The F in F# is for FUN!

4. Halo 3 with F# Skills

5. XBLA: Path to Go – F# AI

6. Facebook: Monopoly

7. F#
• Statically Typed
• Functional
• Object Orientated
• Open Source
• .Net language
• In Visual Studio
& Xamarin Studio

8. F# for Profit
• Time to Market
• Efficiency
• Correctness
• Complexity

9. Time to market
speed development by 50 percent or more,
European IB
order of magnitude increase in productivity,
GameSys

10. Efficiency
processes that used to require hours now take just minutes,
Grange Insurance
performance is 10× better than the C++ that it replaces,
Aviva

11. Correctness
leads to virtually bug-free code,
Fixed Income
I am still waiting for the first bug to come in,
E-On

12. Complexity
everything becomes simple and clear when expressed in F#,
Byron Cook

13. DEMOS

14. Light Syntax: POCOs
F#
type Person(name:string,age:int) =
/// Full name
member person.Name = name
/// Age in years
member person.Age = age
C#
public class Person
{
public Person(string name, int age)
{
_name = name;
_age = age;
}
private readonly string _name;
private readonly int _age;
/// <summary>
/// Full name
/// </summary>
public string Name
{
get { return _name; }
}
/// <summary>
/// Age in years
/// </summary>
public int Age
{
get { return _age; }
}
}

15. Light Syntax: DI
F#
type VerySimpleStockTraderImpl
(analysisService:IStockAnalysisService,
brokerageService:IOnlineBrokerageService) =
interface IAutomatedStockTrader with
member this.ExecuteTrades() =
() // ...
C#
public class VerySimpleStockTraderImpl
: IAutomatedStockTrader
{
private readonly
IStockAnalysisService analysisService;
private readonly
IOnlineBrokerageService brokerageService;
public VerySimpleStockTraderImpl(
IStockAnalysisService analysisService,
IOnlineBrokerageService brokerageService)
{
this.analysisService = analysisService;
this.brokerageService = brokerageService;
}
public void ExecuteTrades()
{
// ...
}
}

16. Unit Testing
F# NUnit
module MathTest =
open NUnit.Framework
let [<Test>] ``2 + 2 should equal 4``() =
Assert.AreEqual(2 + 2, 4)
C# NUnit
using NUnit.Framework;
[TestFixture]
public class MathTest
{
[Test]
public void
TwoPlusTwoShouldEqualFour()
{
Assert.AreEqual(2 + 2, 4);
}
}

17. Mocking
F# Foq
let [<Test>] ``order sends mail if unfilled``() =
// setup data
let order = Order("TALISKER", 51)
let mailer = mock()
order.SetMailer(mailer)
// exercise
order.Fill(mock())
// verify
verify <@ mailer.Send(any()) @> once
C# Moq
public void OrderSendsMailIfUnfilled()
{
// setup data
var order = new Order("TALISKER", 51);
var mailer = new Mock<MailService>();
order.SetMailer(mailer.Object);
// exercise
order.Fill(Mock.Of<Warehouse>());
// verify
mailer.Verify(mock =>
mock.Send(It.IsAny<string>()),
Times.Once());
}

18. Tickspec: Debugging

19. FunScript
TypeScript Type Provider

20. Try F#:
http://tryfsharp.org

21. RESOURCES

22. F# Books

23. F#UNCTIONAL LONDONERS
• 550 Members
• Founded 2010
• Meets every 2 weeks

24. Meet the F#ers
Twitter #fsharp
@rickasaurus
@tomaspetricek
@jonharrop

25. Show me the money!

26. Questions?
Twitter:
@ptrelford
Blog:
http://trelford.com/blog
Foundation:
http://fsharp.org