Phil #SDDConf, London, 2015

Transcription

1 Phil #SDDConf, London, 2015

2 Founded Feb Members Meets every 2 weeks Topics include Machine Learning Finance Games Web

3 Online & offline groups at

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8 Statically Typed Functional First Object Orientated Open Source.Net language In Visual Studio & Xamarin Studio

9 Kaggle Testimonial we have a large existing code base in C#, getting started with F# was an easy decision. The F# code is consistently shorter, easier to read, easier to refactor and contains far fewer bugs. we ve become more productive. Source:

10 Phil #SDDConf, London, 2015

11 Time to Market Efficiency Correctness Complexity

12 speed development by 50 percent or more, European IB order of magnitude increase in productivity, GameSys

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

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

15 Billion-dollar mistake I call it my billion-dollar mistake. It was the invention of the null reference in [ ] I couldn't resist the temptation to put in a null reference, simply because it was so easy to implement. This has led to innumerable errors, vulnerabilities, and system crashes, which have probably caused a billion dollars of pain and damage in the last forty years. Tony Hoare

16 everything becomes simple and clear when expressed in F#, Byron Cook, Microsoft Research

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20 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

21 F# type VerySimpleStockTrader (analysisservice:istockanalysisservice, brokerageservice:ionlinebrokerageservice) = member this.executetrades() = () //... C# public class VerySimpleStockTrader { private readonly IStockAnalysisService analysisservice; private readonly IOnlineBrokerageService brokerageservice; public VerySimpleStockTrader( IStockAnalysisService analysisservice, IOnlineBrokerageService brokerageservice) { this.analysisservice = analysisservice; this.brokerageservice = brokerageservice; } } public void ExecuteTrades() { //... }

22 for i = 1 to 100 do let text = if i % 3 = 0 && i % 5 = 0 then "FizzBuzz" elif i % 3 = 0 then "Fizz" elif i % 5 = 0 then "Buzz" else i.tostring() Console.WriteLine(text)

23 for i = 1 to 100 do match i%3, i%5 with 0, 0 -> "FizzBuzz" 0, _ -> "Fizz" _, 0 -> "Buzz" _, _ -> i.tostring() > Console.WriteLine

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25 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); } }

26 F# Foq let ``order sends mail if unfilled``() = // setup data let order = Order("TALISKER", 51) let mailer = mock() order.setmailer(mailer) // exercise order.fill(mock()) // verify verify <@ 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()); }

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28 open FSharp.Data type Person = JsonProvider<""" { "name":"name", "age":64 } """> let thomas = Person.Parse(""" { "name":"thomas", "age":12 } """) person.age

29 R TYPE PROVIDER

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32 trainings teaching F# software stacks user groups snippets mac and linux cross-platform books and tutorials F# Software Foundation F# community open-source MonoDevelop contributions research support consultancy mailing list

33 // // About Let // // The let keyword is one of the most fundamental parts of F#. // You'll use it in almost every line of F# code you write, so // let's get to know it well! (no pun intended) // [<Koan(Sort = 2)>] module ``about let`` = [<Koan>] let LetBindsANameToAValue() = let x = 50 AssertEquality x

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36 Blog F# exchange: