1. FUNCTIONAL
RUBY

3. ABOUT ME
• Mikhail Bortnyk

4. ABOUT ME
• Mikhail Bortnyk
• Too old for this shit

5. ABOUT ME
• Mikhail Bortnyk
• Too old for this shit
• Work for Amoniac OÜ

6. ABOUT ME
• Mikhail Bortnyk
• Too old for this shit
• Work for Amoniac OÜ
• Ruby developer

7. ABOUT ME
• Mikhail Bortnyk
• Too old for this shit
• Work for Amoniac OÜ
• Ruby developer
• Language researcher

8. ABOUT ME
• Mikhail Bortnyk
• Too old for this shit
• Work for Amoniac OÜ
• Ruby developer
• Language researcher
• kottans.org co-founder

9. ABOUT ME
• Mikhail Bortnyk
• Too old for this shit
• Work for Amoniac OÜ
• Ruby developer
• Language researcher
• kottans.org co-founder
• twitter @mikhailbortnyk

10. LOOK
FOR
JACKIE*
SPECIAL OFFER
*НАЕБЫВАЮ

11. PART ONE
WHY FUNCTIONAL?

12. SIDE EFFECTS
PROBLEM 1.1
• your objects store state

13. SIDE EFFECTS
PROBLEM 1.1
• your objects store state
• your code modifies state

14. SIDE EFFECTS
PROBLEM 1.1
• your objects store state
• your code modifies state
• your other code modifies state too

15. SIDE EFFECTS
PROBLEM 1.1
• your objects store state
• your code modifies state
• your other code modifies state too
• summary: mess

16. SIDE EFFECTS
PROBLEM 1.1
• your objects store state
• your code modifies state
• your other code modifies state too
• summary: mess

17. DATA/CODE ENTITY SHARING
PROBLEM 1.2
• your model stores both your logic and data

18. DATA/CODE ENTITY SHARING
PROBLEM 1.2
• your model stores both your logic and data
• nuff said

19. DATA/CODE ENTITY SHARING
PROBLEM 1.2
• your model stores both your logic and data
• nuff said

20. HYPE
PROBLEM 1.3
• Erlang

21. HYPE
PROBLEM 1.3
• Erlang
• Haskell

22. HYPE
PROBLEM 1.3
• Erlang
• Haskell
• Scala

23. HYPE
PROBLEM 1.3
• Erlang
• Haskell
• Scala
• OCaml

24. HYPE
PROBLEM 1.3
• Erlang
• Haskell
• Scala
• OCaml
• Lisp

25. HYPE
PROBLEM 1.3
• Erlang
• Haskell
• Scala
• OCaml
• Lisp
• Javascript (sic!)

26. HYPE
PROBLEM 1.3
• Erlang
• Haskell
• Scala
• OCaml
• Lisp
• Javascript (sic!)
• Ruby (sic!)

27. PART TWO
EASY (NOT REALLY) LEVEL

28. LIMITS ARE FREEING
CLEAN YOUR RUBY
• David Copeland article “Adventures in functional programming
with Ruby”

29. LIMITS ARE FREEING
CLEAN YOUR RUBY
• David Copeland article “Adventures in functional programming
with Ruby”
• Loops are just functions

30. LIMITS ARE FREEING
CLEAN YOUR RUBY
• David Copeland article “Adventures in functional programming
with Ruby”
• Loops are just functions
• Data structures are just functions

31. LIMITS ARE FREEING
CLEAN YOUR RUBY
• David Copeland article “Adventures in functional programming
with Ruby”
• Loops are just functions
• Data structures are just functions
• Objects are just functions

32. LIMITS ARE FREEING
CLEAN YOUR RUBY
• David Copeland article “Adventures in functional programming
with Ruby”
• Loops are just functions
• Data structures are just functions
• Objects are just functions
• Namespaces are just functions

33. LIMITS ARE FREEING
CLEAN YOUR RUBY
• David Copeland article “Adventures in functional programming
with Ruby”
• Loops are just functions
• Data structures are just functions
• Objects are just functions
• Namespaces are just functions
• P.S. Ruby HAS Tail Call Optimization

34. ROUGH HACK
TAIL-CALL OPTIMIZATION
def fact(n, acc=1)
return acc if n <= 1
fact(n-1, n*acc)
end
RubyVM::InstructionSequence.compile_option = {
tailcall_optimization: true,
trace_instruction: false
}
fact(1000)

35. FUNCTIONAL VS OBJECT-ORIENTED
SIDE TO SIDE COMPARISON
new_person = ->(name, birthdate, gender, title, id=nil) {
return ->(attribute) {
return id if attribute == :id
return name if attribute == :name
return birthdate if attribute == :birthdate
return gender if attribute == :gender
return title if attribute == :title
nil
}
}
class Person
attr_reader :id, :name, :birthdate, :gender, :title
def initialize(name, birthdate, gender, title, id=nil)
@id = id
@name = name
@birthdate = birthdate
@gender = gender
@title = title
end
end

36. SPECIAL KNOWLEDGE
WHAT’S WRONG WITH OO-CODE?
• WTF is “class”

37. SPECIAL KNOWLEDGE
WHAT’S WRONG WITH OO-CODE?
• WTF is “class”
• WTF are .new and initialize

38. SPECIAL KNOWLEDGE
WHAT’S WRONG WITH OO-CODE?
• WTF is “class”
• WTF are .new and initialize
• API of class

39. SPECIAL KNOWLEDGE
WHAT’S WRONG WITH OO-CODE?
• WTF is “class”
• WTF are .new and initialize
• API of class
• WTF are @-variables

40. SPECIAL KNOWLEDGE
WHAT’S WRONG WITH OO-CODE?
• WTF is “class”
• WTF are .new and initialize
• API of class
• WTF are @-variables
• difference between class and instance

41. SPECIAL KNOWLEDGE
WHAT’S WRONG WITH OO-CODE?
• WTF is “class”
• WTF are .new and initialize
• API of class
• WTF are @-variables
• difference between class and instance
• WTF is “attr_reader”

42. NO HIDDEN MAGIC
FUNCTIONAL PROGRAMMING CODE
• how to define function

43. NO HIDDEN MAGIC
FUNCTIONAL PROGRAMMING CODE
• how to define function
• how to call function

44. TO DON’T SHOOT YOUR LEG
SAFETY RULES
• do not modify, create new

45. TO DON’T SHOOT YOUR LEG
SAFETY RULES
• do not modify, create new
• BUY MORE RAM

46. TO DON’T SHOOT YOUR LEG
SAFETY RULES
• do not modify, create new
• BUY MORE RAM
• functions should not depend on environment

47. TO DON’T SHOOT YOUR LEG
SAFETY RULES
• do not modify, create new
• BUY MORE RAM
• functions should not depend on environment
• BUY EVEN MORE RAM

48. TO DON’T SHOOT YOUR LEG
SAFETY RULES
• do not modify, create new
• BUY MORE RAM
• functions should not depend on environment
• BUY EVEN MORE RAM
• avoid returns

49. TO DON’T SHOOT YOUR LEG
SAFETY RULES
• do not modify, create new
• BUY MORE RAM
• functions should not depend on environment
• BUY EVEN MORE RAM
• avoid returns
• use lambdas

50. TO DON’T SHOOT YOUR LEG
SAFETY RULES
• do not modify, create new
• BUY MORE RAM
• functions should not depend on environment
• BUY EVEN MORE RAM
• avoid returns
• use lambdas
• DO NOT FORGET TO ORDER RAM RIGHT NOW

51. SIDE TO SIDE RULES COMPARISON
FUNCTIONAL VS OBJECT-ORIENTED
• how to perform tasks and
how to track changes
• state changes are important
• order of execution is
important
• flow controlled by loops,
conditionals, function calls
• instances of structures and
classes
• focus on what information is
needed and what
transformations required
• state changes are non-existent
• order of execution is low-
important
• flow controlled by function
calls including recursion
• functions are first class
objects, data collections

52. — Greenspun’s tenth rule of programming
ANY SUFFICIENTLY COMPLICATED C OR
FORTRAN PROGRAM CONTAINS AN AD-HOC,
INFORMALLY-SPECIFIED, BUG-RIDDEN, SLOW
IMPLEMENTATION OF HALF OF COMMON LISP.
”
“

53. PART THREE
I AM DEVELOPER, I DON’T WANT
TO LEARN, I WANT PATTERN
MATCHING AND IMMUTABILITY

54. STILL EVOLVING!
FUNCTIONAL-RUBY GEM
• created by Jerry D’Antonio

55. STILL EVOLVING!
FUNCTIONAL-RUBY GEM
• created by Jerry D’Antonio
• inspired by Erlang, Clojure, Haskell and Functional Java

56. STILL EVOLVING!
FUNCTIONAL-RUBY GEM
• created by Jerry D’Antonio
• inspired by Erlang, Clojure, Haskell and Functional Java
• has records, unions and tuples

57. STILL EVOLVING!
FUNCTIONAL-RUBY GEM
• created by Jerry D’Antonio
• inspired by Erlang, Clojure, Haskell and Functional Java
• has records, unions and tuples
• has protocols

58. STILL EVOLVING!
FUNCTIONAL-RUBY GEM
• created by Jerry D’Antonio
• inspired by Erlang, Clojure, Haskell and Functional Java
• has records, unions and tuples
• has protocols
• has Erlang-style pattern matching

59. STILL EVOLVING!
FUNCTIONAL-RUBY GEM
• created by Jerry D’Antonio
• inspired by Erlang, Clojure, Haskell and Functional Java
• has records, unions and tuples
• has protocols
• has Erlang-style pattern matching
• has function memoization

60. STILL EVOLVING!
FUNCTIONAL-RUBY GEM
• created by Jerry D’Antonio
• inspired by Erlang, Clojure, Haskell and Functional Java
• has records, unions and tuples
• has protocols
• has Erlang-style pattern matching
• has function memoization
• supports MRI, JRuby and Rubinius

61. FUNCTIONAL-RUBY GEM
SHORT OVERVIEW

62. PATTERN MATCHING AND TYPE CHECKING
FUNCTIONAL-RUBY GEM
class Yoga
include Functional::PatternMatching
include Functional::TypeCheck
defn(:where_is_sun) do
puts "o"
end
defn(:where_is_sun, 14) do
puts "88!"
end
defn(:where_is_sun, _) do |name|
puts "o, #{name}!"
end
defn(:where_is_sun, _) do |name|
puts "Are you in wrong district, #{name.rude_name}?"
end.when { |name| Type?(name, Moskal) }
defn(:where_is_sun, _, _) do |name, surname|
"o, #{name} #{surname}!"
end
end

63. MEMOIZATION
FUNCTIONAL-RUBY GEM
class Factors
include Functional::Memo
def self.sum_of(number)
of(number).reduce(:+)
end
def self.of(number)
(1..number).select {|i| factor?(number, i)}
end
def self.factor?(number, potential)
number % potential == 0
end
memoize(:sum_of)
memoize(:of)
end

64. RECORDS
FUNCTIONAL-RUBY GEM
Name = Functional::Record.new(:first, :middle, :last, :suffix) do
mandatory :first, :last
default :first, 'J.'
default :last, 'Doe'
end

65. QUESTION

66. Q&A

67. THANK YOU