A comparison between the programming languages Scala and Ruby

1. SCALA VS RUBY
Rémy-Christophe Schermesser
rcs@octo.com
@El_Picador
1

2. 2

3. 3

4. 4

5. 5

6. 6

7. 7

8. <relationships>
<ejb-relation>
<ejb-relation-name>a-b</ejb-relation-name>
<ejb-relationship-role>
<!-- A => B -->
<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>
<!-- B => A -->
<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

9. 9

10. Functional
programming
10

11. Functional APIs
programming
10

12. Functional APIs
programming
gems
10

13. Functional APIs
programming
Easy to use gems
10

14. 11

15. Functional
programming ?
12

16. Functional
programming ?
12

17. Functional APIs ?
programming ?
12

18. Functional APIs ?
programming ?
12

19. Functional APIs ?
programming ?
gems ?
12

20. Functional APIs ?
programming ?
gems ?
12

21. Functional APIs ?
programming ?
Easy to use ? gems ?
12

22. Functional APIs ?
programming ?
Easy to use ? gems ?
12

23. VS
13

24. FIGHT
VS
13

25. DRAW
VS
Sort of ...
13

26. WHY A DRAW ?
14

27. WHY A DRAW ?
let’s talk about languages
14

28. WHY A DRAW ?
let’s talk about languages
let’s frameworkise
14

29. WHY A DRAW ?
let’s talk about languages
let’s frameworkise
let’s deploy
14

30. WHY A DRAW ?
let’s talk about languages
let’s frameworkise
let’s deploy
let’s meet people
14

31. 15

32. LET’S TALK ABOUT
LANGUAGES
15

33. 16

34. THE
BEST THING ABOUT
SCALA & RUBY
16

35. No
at the end of lines
17

36. No
;
at the end of lines
17

37. Scala No Ruby
1 ; 1
at the end of lines
17

38. 18

39. λ
18

40. list.filter(_ % 2 == 0)
list.filter {
e: Int => (e % 2 == 0))
}
19

41. list.filter(_ % 2 == 0)
list.filter {
e: Int => (e % 2 == 0))
}
list.select do |e|
e % 2 == 0
end
19

42. list.filter(_ % 2 == 0)
Scala
list.filter {
}
Ruby
e: Int => (e % 2 == 0))
2 2
list.select do |e|
e % 2 == 0
end
19

43. TYPES !
20

44. TYPES ! STATIC
20

45. TYPES ! STATIC
var hash =
new HashMap[Int, String]
20

46. TYPES ! STATIC
var hash =
new HashMap[Int, String]
hash = Hash.new
hash = 3
20

47. TYPES ! STATIC
var hash =
new HashMap[Int, String]
hash = Hash.new
hash = 3
20

48. TYPES ! STATIC
Scala Ruby
2 2
var hash =
new HashMap[Int, String]
hash = Hash.new
hash = 3
20

49. PATTERN
MATCHING
21

50. 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

51. gem install case
22

52. 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

53. 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

54. 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

55. MONKEY
PATCHING
23

56. puts "a".to_s # => a
24

57. puts "a".to_s # => a
class String
def to_s
"Monkey !"
end
def my_method
"Patch !"
end
end
24

58. puts "a".to_s # => a
class String
def to_s
"Monkey !"
end
def my_method
"Patch !"
end
end
puts "a".to_s # => Monkey !
24

59. puts "a".to_s # => a
class String
def to_s
"Monkey !"
end
def my_method
"Patch !"
end
end
puts "a".to_s # => Monkey !
puts "a".my_method # => Patch !
24

60. 25

61. Implicit !
25

62. Implicit !
class MySuperString(original: String) {
def myMethod = "Patch !"
}
25

63. Implicit !
class MySuperString(original: String) {
def myMethod = "Patch !"
}
implicit def string2super(x: String) =
new MySuperString(x)
25

64. Implicit !
class MySuperString(original: String) {
def myMethod = "Patch !"
}
implicit def string2super(x: String) =
new MySuperString(x)
println("a".myMethod) // => Patch !
25

65. Implicit !
Scala Ruby
class MySuperString(original: String) {
}
def myMethod = "Patch !"
3 3
implicit def string2super(x: String) =
new MySuperString(x)
println("a".myMethod) // => Patch !
25

66. Dynamic calls
26

67. 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

68. 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

69. 27

70. Scala 2.9
27

71. 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

72. 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
}
}
val animal = new Animal
animal.qualk // => Animal says qualk
animal.say("hello") // => Animal wants to say hello
27

73. 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
}
}
val animal = new Animal
animal.qualk // => Animal says qualk
animal.say("hello") // => Animal wants to say hello
27

74. Scala 2.9
Scala
class Animal extends Dynamic {
Ruby
def _select_(name: String) = println("Animal says " + name)
def _invoke_(name: String, args: Any*) = {
4 4
println("Animal wants to " + name + args.mkString(", "))
this
}
}
val animal = new Animal
animal.qualk // => Animal says qualk
animal.say("hello") // => Animal wants to say hello
27

75. Traits !
trait PimpMyClass {
def myMethod = println("myMethod")
}
class IncludeTrait extends PimpMyClass
(new IncludeTrait).myMethod
28

76. Traits !
trait PimpMyClass {
def myMethod = println("myMethod")
}
class IncludeTrait extends PimpMyClass
(new IncludeTrait).myMethod
28

77. Modules !
module PimpMyClass
def my_method
puts "my_method"
end
end
class IncludeModule
include PimpMyClass
end
IncludeModule.new.my_method
29

78. 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

79. DUCK
TYPING
30

80. DUCK
TYPING
It quacks !
30

81. DUCK
TYPING
It quacks !
It walks !
30

82. DUCK
TYPING
It quacks !
It walks !
30

83. class Duck
def quack; end
def walk; end
end
31

84. class Duck
def quack; end
def walk; end class Platypus
end def quack; end
def walk; end
end
31

85. class Duck
def quack; end
def walk; end class Platypus
end def quack; end
def walk; end
end
def act_as_a_duck animal
animal.quack
animal.walk
end
31

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

87. class Duck {
def quack = ...
def walk = ...
}
32

88. class Duck {
def quack = ...
def walk = ... class Platypus {
} def quack = ...
def walk = ...
}
32

89. class Duck {
def quack = ...
def walk = ... class Platypus {
} def quack = ...
def walk = ...
}
def ActAsADuck(a: { def quack; def walk })= {
a.quack
a.walk
}
32

90. class Duck {
def quack = ...
def walk = ... class Platypus {
} def quack = ...
def walk = ...
}
def ActAsADuck(a: { def quack; def walk })= {
a.quack
a.walk
} val duck = new Duck
val platypus = new
Platypus
ActAsADuck(duck)
ActAsADuck(platypus)
32

91. class Duck {
def quack = ...
def walk = ...
Scala Ruby
class Platypus {
} def quack = ...
def walk = ...
}
}
6
a.quack
a.walk
6
def ActAsADuck(a: { def quack; def walk })= {
val duck = new Duck
val platypus = new
Platypus
ActAsADuck(duck)
ActAsADuck(platypus)
32

92. ≃
33

93. ≃
Only learn the
syntax
33

94. 34

95. LET’S FRAMEWORKISE
34

96. 35

97. Test::Unit
rSpec
35

98. UNIT TESTING
36

99. test "my test" do
array = [1, 2, 3]
assert_equal 1, array.first
end
UNIT TESTING
36

100. 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

101. SPEC TESTING
37

102. 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

103. 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

104. 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

105. 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

106. Test::Unit
rSpec
39

107. Test::Unit
Scala Ruby
rSpec
7 7
39

108. 40

109. 40

110. 40

111. 40

112. 41

113. 24 000
gems
41

114. for Rails
12 000
gems
41

115. for Rails
12 000
gems
41

116. for Rails
Scala 000
12 Ruby
7 8
gems
41

117. 42

118. Actors in Ruby ?
43

119. Don’t try this at
home !
43

120. Scala try Ruby
Don’t this at
8home ! 8
43

121. 44

122. 45

123. LET’S DEPLOY
45

124. 46

125. rails new myapp
heroku create myapp
git push heroku master
46

126. rails new myapp
heroku create myapp
git push heroku master
http://myapp.heroku.com
46

127. Scala Ruby
8
rails new myapp
heroku create myapp9
git push heroku master
http://myapp.heroku.com
46

128. 47

129. 47

130. 47

131. 47

132. 47

133. 47

134. 47

135. 47

136. 80
60
40
70,74
39,74 20
2,07
0
Average performance
(less is better) Source : http://shootout.alioth.debian.org
48

137. Scala JRuby Ruby 1.9
80
60
40
70,74
39,74 20
2,07
0
Average performance
(less is better) Source : http://shootout.alioth.debian.org
48

138. Scala JRuby Ruby 1.9
80
Scala Ruby 60
9 39,74
9
70,74
20
40
2,07
0
Average performance
(less is better) Source : http://shootout.alioth.debian.org
48

139. Do not talk of
Ruby
to an admin
49

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

141. 50

142. LET’S MEET PEOPLE
50

143. 51

144. 51

145. 52

146. 52

147. «Most Java Programmers
are Morons»
53

148. «Most Java Programmers
are Morons»
© Rails community
53

149. Scala Ruby
9 9
54

150. ?
?
55

151. ?
?
55

152. 56