Why learn new programming languages

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

PERSONAL HISTORY OF PROGRAMMING LANGUAGES 4

QBasic Turbo Pascal Delphi VBScript
(1996) (1998) (1999) (2001)

C# JavaScript Java Python Scheme Ruby
(2002) (2003) (2004) (2005) (2006) (2010)

PERSONAL HISTORY OF PROGRAMMING LANGUAGES 5

QBasic Turbo Pascal Delphi VBScript
(1996) (1998) (1999) (2001)

C# JavaScript Java Python Scheme Ruby
(2002) (2003) (2004) (2005) (2006) (2010)

HIGHER ORDER FUNCTIONS 6

Formulating Abstractions with
Higher-Order Functions

ABSTRACTIONS THROUGH FUNCTIONS 7

(* 3 3 3) ; outputs 27

(define (cube x)
(* x x x))

(cube 3) ; outputs 27


(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))))


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


(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

ABSTRACTIONS THROUGH FUNCTIONS - JAVASCRIPT 13

$("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...
});

ABSTRACTIONS THROUGH FUNCTIONS – C# 14

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; }

OBJECTS FROM CLOSURES 15

You don’t need classes
to create objects

OBJECTS FROM CLOSURES IN SCHEME 16

(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

OBJECTS FROM CLOSURES IN JAVASCRIPT 17

var 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

READABILITY 18

Extreme emphasis
on expressiveness

READABILITY 19

“[…] 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…”

EXAMPLES OF RUBY IDIOMS 20

abort unless str.include? "OK"

x = x * 2 until x > 100

3.times { puts "olleh" }

10.days_ago
2.minutes + 30.seconds

1.upto(100) do |i|
puts i
end

EXAMPLE OF RSPEC TEST 21

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

C# UNIT TEST INFLUENCED BY RSPEC 22

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();
}
}

C# FLUENT ASSERTIONS 23

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);

READABILITY 24

Internal DSLs and
Fluent Interfaces

RUBY DSL EXAMPLES - MARKABY 25

RUBY DSL EXAMPLES – ENUMERABLE PROXY API 26

C# LINQ EXAMPLE 27

static 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 Asbjørnsen
Jonas Follesø
Ole Hansen

C# STORYQ EXAMPLE 28

[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());
}

C# OBJECT BUILDER PATTERN 29

[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);
}

MONKEY PATCHING 30

Runtime generation of code
and behaviour

RUBY ACTIVE RECORD AND METHOD MISSING 31

C# DYNAMIC AND EXPANDO OBJECT 32

static 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)

C# MONKEY PATCHING 33

public 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>

C# MICRO ORMS 34

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

• Massive
• Simple.Data
• Peta Pico
• Dapper

C# MICRO ORMS 35

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

SAPIR–WHORF HYPOTHESIS 36

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

37

TAKK FOR MEG

Jonas Follesø

Why learn new programming languages

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