WHY LEARN NEW PROGRAMMING

LANGUAGES?

What I’ve learned from Ruby and Scheme that applies to my daily work in C# and

JavaScript

Trondheim XP Meetup

Jonas Follesø, Scientist/Manager BEKK Trondheim

08/02/2012

3

4PERSONAL HISTORY OF PROGRAMMING LANGUAGES

QBasic(1996)

Turbo Pascal(1998)

Delphi(1999)

VBScript(2001)

C#(2002)

JavaScript(2003)

Java(2004)

Python(2005)

Scheme(2006)

Ruby(2010)

5PERSONAL HISTORY OF PROGRAMMING LANGUAGES

QBasic(1996)

Turbo Pascal(1998)

Delphi(1999)

VBScript(2001)

C#(2002)

JavaScript(2003)

Java(2004)

Python(2005)

Scheme(2006)

Ruby(2010)

6HIGHER ORDER FUNCTIONS

Formulating Abstractions with Higher-Order

Functions

7ABSTRACTIONS THROUGH FUNCTIONS

(* 3 3 3) ; outputs 27

(define (cube x)   (* x x x))  (cube 3) ; outputs 27

8ABSTRACTIONS THROUGH FUNCTIONS

(define (sum-int a b)  (if (> a b)      0      (+ a (sum-int (+ a 1) b))))

(define (sum-cubes a b)  (if (> a b)      0      (+ (cube a) (sum-cubes (+ a 1) b))))

9ABSTRACTIONS THROUGH FUNCTIONS

(define (sum-int a b)  (if (> a b)      0      (+ a (sum-int (+ a 1) b))))

(define (sum-cubes a b)  (if (> a b)      0      (+ (cube a) (sum-cubes (+ a 1) b))))

10ABSTRACTIONS THROUGH FUNCTIONS

(define (<name> a b)  (if (> a b)      0      (+ <term> (<name> (<next> a) b))))

11ABSTRACTIONS THROUGH FUNCTIONS

(define (sum term a next b)  (if (> a b)      0      (+ (term a) (sum term (next a) next b))))

(define (inc n) (+ n 1))(define (identity n) n)

(define (sum-int a b) (sum identity a inc b))(define (sum-cubes a b) (sum cube a inc b))

(sum-int 0 10) ; outputs 55(sum-cubes 0 10) ; outputs 3025

12ABSTRACTIONS THROUGH FUNCTIONS

(define (sum term a next b)  (if (> a b)      0      (+ (term a) (sum term (next a) next b))))

(define (inc n) (+ n 1))(define (identity n) n)

(define (sum-int a b) (sum identity a inc b))(define (sum-cubes a b) (sum cube a inc b))

(sum-int 0 10) ; outputs 55(sum-cubes 0 10) ; outputs 3025

13ABSTRACTIONS THROUGH FUNCTIONS - JAVASCRIPT

$("li").click(function() {    $(this).css({'color':'yellow'});});

$("li").filter(function(index) {    return index % 3 == 2;}).css({'color':'red'});

$.get("/some-content", function(data) {    // update page with data...});

14ABSTRACTIONS THROUGH FUNCTIONS – C#

SumEvenCubes(1, 10); // outputs 1800

public int SumEvenCubes() {    var num = new[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};    return num .Where(IsEven) .Select(Cube) .Aggregate(Sum);}

public bool IsEven(int n) { return n % 2 == 0; }public int Cube(int n) { return n*n*n; }public int Sum(int a, int b) { return a + b; }

15OBJECTS FROM CLOSURES

You don’t need classes to create objects

16OBJECTS FROM CLOSURES IN SCHEME (define (make-account balance)

  (define (withdraw amount)    (if (>= balance amount)        (set! balance (- balance amount))        "Insufficient funds"))    (define (deposit amount)    (set! balance (+ balance amount))    balance)    (define (dispatch m . args)    (case m      ((withdraw) (apply withdraw args))      ((deposit) (apply deposit args))))    dispatch)

(define account1 (make-account 100))(account1 'withdraw 50)(account1 'deposit 25) ; outputs 75

17OBJECTS FROM CLOSURES IN JAVASCRIPTvar make_account = function (balance) {    var withdraw = function (amount) {        if (balance >= amount) balance -= amount;        else throw "Insufficient funds";         return balance;    };     var deposit = function (amount) {        balance += amount;        return balance;    };     return {        withdraw: withdraw,        deposit: deposit    };};

var account1 = make_account(100);account1.withdraw(50);account1.deposit(25); // outputs 75

18READABILITY

Extreme emphasis on expressiveness

19READABILITY

“[…] we need to focus on humans, on how humans care about doing programming or operating the application of the machines. We are the masters. They are the slaves…”

20EXAMPLES OF RUBY IDIOMS

abort unless str.include? "OK"

x = x * 2 until x > 100

3.times { puts "olleh" }

10.days_ago2.minutes + 30.seconds

1.upto(100) do |i|  puts iend

21EXAMPLE OF RSPEC TEST

describe Bowling do    it "should score 0 for gutter game" do        bowling = Bowling.new        20.times { bowling.hit(0) }        bowling.score.should == 0    endend

22C# UNIT TEST INFLUENCED BY RSPEC

public class Bowling_specs {    public void Should_score_0_for_gutter_game() {        var bowling = new Bowling();        20.Times(() => bowling.Hit(0));        bowling.Score.Should().Be(0);    }}

public static class IntExtensions {    public static void Times(this int times, Action action) {        for (int i = 0; i <= times; ++i)            action();    }}

23C# FLUENT ASSERTIONS

string actual = "ABCDEFGHI";

actual.Should().StartWith("AB") .And.EndWith("HI") .And.Contain("EF") .And.HaveLength(9);

IEnumerable collection = new[] { 1, 2, 3 };collection.Should().HaveCount(4, "we put three items in collection"))collection.Should().Contain(i => i > 0);

24READABILITY

Internal DSLs andFluent Interfaces

25RUBY DSL EXAMPLES - MARKABY

26RUBY DSL EXAMPLES – ENUMERABLE PROXY API

27C# LINQ EXAMPLEstatic void Main(string[] args){ var people = new[] { new Person { Age=28, Name = "Jonas Follesø"}, new Person { Age=25, Name = "Per Persen"}, new Person { Age=55, Name = "Ole Hansen"}, new Person { Age=40, Name = "Arne Asbjørnsen"}, };

var old = from p in people where p.Age > 25 orderby p.Name ascending select p;

foreach(var p in old) Console.WriteLine(p.Name);}

---Arne AsbjørnsenJonas FollesøOle Hansen

28C# STORYQ EXAMPLE[Test]public void Gutter_game(){ new Story("Score calculation") .InOrderTo("Know my performance") .AsA("Player") .IWant("The system to calculate my total score") .WithScenario("Gutter game") .Given(ANewBowlingGame) .When(AllOfMyBallsAreLandingInTheGutter) .Then(MyTotalScoreShouldBe, 0) .WithScenario("All strikes") .Given(ANewBowlingGame) .When(AllOfMyBallsAreStrikes) .Then(MyTotalScoreShouldBe, 300) .ExecuteWithReport(MethodBase.GetCurrentMethod()); }

29C# OBJECT BUILDER PATTERN[Test]public void Should_generate_shipping_statement_for_order(){ Order order = Build

.AnOrder() .ForCustomer(Build.ACustomer()) .WithLine("Some product", quantity: 1) .WithLine("Some other product", quantity: 2);

var orderProcessing = new OrderProcessing(); orderProcessing.ProcessOrder(order);}

30MONKEY PATCHING

Runtime generation of codeand behaviour

31RUBY ACTIVE RECORD AND METHOD MISSING

32C# DYNAMIC AND EXPANDO OBJECTstatic void Main(string[] args){ dynamic person = new ExpandoObject(); person.Name = "Jonas Follesø"; person.Age = 28;

Console.WriteLine("{0} ({1})", person.Name, person.Age);}

Jonas Follesø (28)

33C# MONKEY PATCHINGpublic class DynamicRequest : DynamicObject{ public override bool TryGetMember(GetMemberBinder binder, out object result) { string key = binder.Name; result = HttpContext.Current.Request[key] ?? ""; return true; }}

@using MvcApplication1.Controllers@{ Page.Request = new DynamicRequest();}

<h4>Hello @Page.Request.Name</h4><h4>Hello @HttpContext.Current.Request["Name"]</h4>

34C# MICRO ORMS

• Afrer C# 4.0 with support for dynamic typing a whole new category of micro ORMs has emerged:

• Massive

• Simple.Data

• Peta Pico

• Dapper

35C# MICRO ORMS

IEnumerable<User> u = db.Users.FindAllByName("Bob").Cast<User>();

db.Users.FindByNameAndPassword(name, password)// SELECT * FROM Users WHERE Name = @p1 and Password = @p2

db.Users.FindAllByJoinDate("2010-01-01".to("2010-12-31"))// SELECT * FROM [Users] WHERE [Users].[JoinDate] <= @p1

36SAPIR–WHORF HYPOTHESIS

The principle of linguistic relativity holds that the structure of a language affects the ways in which its speakers are able to conceptualize their world, i.e. their world view.

http://en.wikipedia.org/wiki/Linguistic_relativity

TAKK FOR MEG

Jonas Follesø

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