This document discusses similarities and differences between Ruby and Scala. Some key points made include: - Both languages support features like maps, filters, and reduce functions on collections, though the naming is sometimes different (e.g. Traversable#map in Scala vs. Enumerable#map in Ruby). - Both support traits/modules for mixing in functionality like Ruby's modules and Scala's traits. - Both support open classes through mechanisms like Ruby's open class and Scala's implicit conversions. - Both support dynamic invocation through method_missing in Ruby and Scala's dynamic feature. - Scala supports additional features like futures, Scala.js for compiling to JavaScript, and Scala

1. Rubyist Scala
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2. • (Matsukubo Yuto)
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• Ruby
• )Socket Ruby Scala
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3. T

6. Rubyist
Scala
Kawasaki.rb Ruby

7. Scala
?✋

8. Rubyist Scala

9. • Ruby
Scala
•
(Rubyist )
•

10. Scala

11. Scala
•
• JVM ( .NET )
• Java BetterJava

12. Ruby ?

13. Ruby ( )
•
•
• Mix-In
• Open Class
• method_missing
•

14. Ruby ( )
•
•
• Mix-In
• Open Class
• method_missing
•
Scala !

16. Ruby
1 + 2 # => 3
1.+(2) # => 3

17. Scala
1 + 2 // => 3
1.+(2) // => 3

18. Scala
class MyClass {
// ()
def smile: String = {
" :-)"
}
//
def smile(str: String): String = {
str + " :-)"
}
// {}
def smile2(str: String) = str + " :-)"
}

19. Scala
val obj = new MyClass
// ()
//
obj.smile
//
obj.smile("Hi,")
// 1 ()
obj smile "Hi,"

21. Ruby
• Enumerable#map(collect)
• Enumerable#flat_map
• Enumerable#reduce(inject)
• Enumerable#select
• Enumerable#find
• etc…

22. Scala
• Traversable#map
• Traversable#flatMap
• Traversable#reduceLeft
• Traversable#filter
• Traversable#find
• etc…

23. : Ruby map
[1, 2, 3, 4].map { |i| i * 2 }
# => [2, 4, 6, 8]

24. Scala
List(1, 2, 3, 4).map { i => i * 2 }
// => List(2, 4, 6, 8)
Ruby !

25. Scala ( )
List(1, 2, 3, 4).map { _ * 2 }
// => List(2, 4, 6, 8)

26. Q. ?
A. Ruby
• Scala map
List(1,2,3).map { i => i * 2 }
List(1,2,3).map( i => i * 2 )
Scala {}

27. Ruby lambda
# Ruby
f = lambda { |i| i + 10 }
f.call(20) # => 30
// Scala
val f = (i: Int) => i + 10
f(20) // => 30

28. :size or length?
• List
• size length (size length )
•
Ruby
List(1,2,3).length // => 3
List(1,2,3).size // => 3

29. Mix-In

30. Ruby module Mix-in
module Monster
def roar
' '
end
end
class Godzilla
include Monster
end
Godzilla.new.roar # => " "

31. Scala Trait
trait Monster {
def roar = " "
}
class Godzilla extends Monster
(new Godzilla).roar // => " "

32. trait Monster {
def roar = " "
}
trait HasTail {
def swing = " "
}
class Godzilla
extends Monster with HasTail

33. trait Monster {
def roar: String
}
class Godzilla extends Monster {
def roar = " "
}
(new Godzilla).roar // => " "

34. Open Class

35. Ruby Open Class
class String
def replace_to_scala
self.gsub('ruby', 'scala')
end
end
"ruby is nice!".replace_to_scala
# => "scala is nice!"

36. Scala Open Class( )
implicit class MyString(val s: String)
def replaceToScala = {
s.replaceAll("ruby", "scala")
}
}
"ruby is nice!".replaceToScala
// String = scala is nice!

37. implicit class MyString(val s: String)
def replaceToScala = {
s.replaceAll("ruby", "scala")
}
}
"ruby is nice!".replaceToScala
// String = scala is nice!

38. implicit conversion
•
•
def concat(i: String, j: String): String = {
i + j
}
implicit def intToString(src: Int): String = {
src.toString
}
concat(100, 200) // => 100200

39. method_missing

40. Ruby method_missing
class MyClass
def method_missing(name)
"#{name} is missing!!"
end
end
MyClass.new.foo
# => "foo is missing!!"

41. Scala method_missing
(Dynamic )
import scala.language.dynamics
class MyClass extends Dynamic {
def selectDynamic(name: String): String = {
s"${name} is missing!"
}
}
(new MyClass).foo // => foo is missing!

42. Duck Typing

43. Ruby Duck Typing
•

44. Scala Duck Typing
(Structural Subtyping)
•
•
• : roar

45. 1.
type Roarabel = {
def roar: String
}

46. 2.
class KingGhidorah {
def roar: String = " "
}
class Mothra {
def roar: String = " "
}

47. 3.
def doRoar(target: Roarabel) = {
target.roar
}
doRoar(new KingGhidorah)
// => “ ”
doRoar(new Mothra)
// => “ ”

48. Scala
•
• Future
• Scala.js … JS Scala
• Scala Native … Scala LLVM
• Dotty … Scala

49. • Scala
• Ruby Scala
• Rubyist Scala !