Scala vs Ruby

SCALA VS RUBY
Rémy-Christophe Schermesser
rcs@octo.com
@El_Picador

1

<relationships>
<ejb-relation>
<ejb-relation-name>a-b</ejb-relation-name>
<ejb-relationship-role>

<ejb-relationship-role-name>a2b</ejb-
relationship-role-name>
<multiplicity>One</multiplicity>
<relationship-role-source>
<ejb-name>A</ejb-name>
</relationship-role-source>
<cmr-field>
<cmr-field-name>b</cmr-field-name>
</cmr-field>
</ejb-relationship-role>
<ejb-relationship-role>

<ejb-relationship-role-name>b2a</ejb-
relationship-role-name>
<multiplicity>One</multiplicity>
<relationship-role-source>
<ejb-name>B</ejb-name>
</relationship-role-source>
</ejb-relationship-role>
</ejb-relation>
</relationships>

8

Functional
programming

10

Functional APIs
programming

10

Functional APIs
programming

gems

10

Functional APIs
programming

Easy to use gems

10

Functional
programming ?

12

Functional APIs ?
programming ?

12

Functional APIs ?
programming ?

gems ?

12

Functional APIs ?
programming ?

Easy to use ? gems ?

12

DRAW
VS

Sort of ...
13

WHY A DRAW ?

let’s talk about languages

14

WHY A DRAW ?


let’s frameworkise

14

WHY A DRAW ?



let’s deploy

14

WHY A DRAW ?



let’s deploy
let’s meet people
14

LET’S TALK ABOUT
LANGUAGES

15

THE
BEST THING ABOUT
SCALA & RUBY
16

No

at the end of lines

17

No
;
at the end of lines

17

Scala No Ruby
1 ; 1
at the end of lines

17

list.filter(_ % 2 == 0)

list.filter {
e: Int => (e % 2 == 0))
}

19


list.filter {
e: Int => (e % 2 == 0))
}

list.select do |e|
e % 2 == 0
end
19


Scala
list.filter {

}
Ruby
e: Int => (e % 2 == 0))

2 2
list.select do |e|
e % 2 == 0
end
19

TYPES ! STATIC

var hash =
new HashMap[Int, String]

20

TYPES ! STATIC

var hash =

hash = Hash.new
hash = 3
20

TYPES ! STATIC
Scala Ruby
2 2
var hash =

hash = Hash.new
hash = 3
20

PATTERN
MATCHING

21

PATTERN
MATCHING
def matchTest(x: Any): Any =
x match {
case 1 => "one"
case "two" => 2
case y: Int => "scala.Int"
case 2 :: tail => tail
}

21

gem install case

22

gem install case

require 'case'

def matchTest x
case x
when 1
"one"
when "two"
2
when Case::All[Integer]
"ruby.Integer"
when Case::Array[2, Case::Any]
x[1..-1]
end
end
22

gem install case

require 'case'

Scala
def matchTest x
case x
when 1
Ruby
3 2
"one"
when "two"
2
when Case::All[Integer]
"ruby.Integer"
when Case::Array[2, Case::Any]
x[1..-1]
end
end
22

puts "a".to_s # => a

24


class String
def to_s
"Monkey !"
end

def my_method
"Patch !"
end
end

24


class String
def to_s
"Monkey !"
end

def my_method
"Patch !"
end
end

puts "a".to_s # => Monkey !

24


class String
def to_s
"Monkey !"
end

def my_method
"Patch !"
end
end

puts "a".to_s # => Monkey !

puts "a".my_method # => Patch !

24

Implicit !

class MySuperString(original: String) {
def myMethod = "Patch !"
}

25

Implicit !

}

implicit def string2super(x: String) =
new MySuperString(x)

25

Implicit !

}


println("a".myMethod) // => Patch !

25

Implicit !

Scala Ruby

}

3 3

println("a".myMethod) // => Patch !

25

Dynamic calls
class Animal

def method_missing name, *args
if args.empty?
puts "Animal says " + name.to_s
else
puts "Animal wants to " + name.to_s + args.join(", ")
end
self
end

end

26

Dynamic calls
class Animal

def method_missing name, *args
if args.empty?
puts "Animal says " + name.to_s
else
puts "Animal wants to " + name.to_s + args.join(", ")
end
self
end

end

animal = Animal.new

animal.qualk # => Animal says : qualks !
animal.say("hello") # => Animal wants to say hello

26

Scala 2.9
class Animal extends Dynamic {
def _select_(name: String) = println("Animal says " + name)

def _invoke_(name: String, args: Any*) = {
println("Animal wants to " + name + args.mkString(", "))
this
}

}

27

Scala 2.9

this
}

}

val animal = new Animal
animal.qualk // => Animal says qualk
animal.say("hello") // => Animal wants to say hello

27

Scala 2.9
Scala

Ruby


4 4
this
}

}

val animal = new Animal
animal.qualk // => Animal says qualk
animal.say("hello") // => Animal wants to say hello

27

Traits !
trait PimpMyClass {
def myMethod = println("myMethod")
}

class IncludeTrait extends PimpMyClass

(new IncludeTrait).myMethod

28

Modules !
module PimpMyClass
def my_method
puts "my_method"
end
end

class IncludeModule
include PimpMyClass
end

IncludeModule.new.my_method

29

Modules !
Scala
module PimpMyClass
def my_method Ruby
puts "my_method"

5 5
end
end

class IncludeModule
include PimpMyClass
end

IncludeModule.new.my_method

29

DUCK
TYPING

It quacks !

30

DUCK
TYPING

It quacks !
It walks !

30

class Duck
def quack; end
def walk; end
end

31

class Duck
def quack; end
def walk; end class Platypus
end def quack; end
def walk; end
end

31

class Duck
def quack; end
end def quack; end
def walk; end
end

def act_as_a_duck animal
animal.quack
animal.walk
end

31

class Duck
def quack; end
end def quack; end
def walk; end
end

def act_as_a_duck animal
animal.quack
animal.walk duck = Duck.new
end platypus = Platypus.new

act_as_a_duck(duck)
act_as_a_duck(platypus)

31

class Duck {
def quack = ...
def walk = ...
}

32

class Duck {
def quack = ...
def walk = ... class Platypus {
} def quack = ...
def walk = ...
}

32

class Duck {
def quack = ...
} def quack = ...
def walk = ...
}

def ActAsADuck(a: { def quack; def walk })= {
a.quack
a.walk
}

32

class Duck {
def quack = ...
} def quack = ...
def walk = ...
}

a.quack
a.walk
} val duck = new Duck
val platypus = new
Platypus

ActAsADuck(duck)
ActAsADuck(platypus)
32

class Duck {
def quack = ...
def walk = ...

Scala Ruby
class Platypus {
} def quack = ...
def walk = ...
}

}
6
a.quack
a.walk
6

val duck = new Duck
val platypus = new
Platypus

ActAsADuck(duck)
ActAsADuck(platypus)
32

≃
Only learn the
syntax
33

LET’S FRAMEWORKISE

34

Test::Unit

rSpec

35

test "my test" do
array = [1, 2, 3]
assert_equal 1, array.first
end

UNIT TESTING

36

test "my test" do
array = [1, 2, 3]
assert_equal 1, array.first
end

UNIT TESTING
@Test def myTest() {
val array = List(1, 2, 3)
assert(array(0) === 1)
}
36

describe "Get of Array" do
it "first returns the first element" do
array = [1, 2, 3]
array.first.should == 1
end
end

SPEC TESTING

37

describe "Get of Array" do
it "first returns the first element" do
array = [1, 2, 3]
array.first.should == 1
end
end

SPEC TESTING
describe("Get of List") {
it("(0) returns the first element") {
val array = List(1, 2, 3)
array(0) should be 1
}
}
37

BDD TESTING

Feature: The user can get an element off an array
Scenario: first is invoked on the array
Given a non-empty array
When first is invoked on the array
Then the first element should be returned

38

Test::Unit

rSpec

39

Test::Unit

Scala Ruby
rSpec
7 7

39

for Rails

12 000
gems
41

for Rails
Scala 000
12 Ruby
7 8
gems
41

Actors in Ruby ?

43

Don’t try this at
home !
43

Scala try Ruby
Don’t this at
8home ! 8

43

rails new myapp
heroku create myapp
git push heroku master

46

rails new myapp
heroku create myapp

http://myapp.heroku.com

46

Scala Ruby
8
rails new myapp
heroku create myapp9

http://myapp.heroku.com

46

80

60

40
70,74
39,74 20

2,07
0

Average performance
(less is better) Source : http://shootout.alioth.debian.org
48

Scala JRuby Ruby 1.9
80

60

40
70,74
39,74 20

2,07
0

Average performance
48

Scala JRuby Ruby 1.9
80

Scala Ruby 60

9 39,74
9
70,74

20
40

2,07
0

Average performance
48

Do not talk of
Ruby
to an admin
49

Do not talk of
Ruby
to an admin
Neither of Java
49

LET’S MEET PEOPLE

50

«Most Java Programmers
are Morons»

53

Scala vs Ruby

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