Requiem for a dream

Presented at Deccan Ruby Conf, Pune in July'14.

Ruby is a delightful programming language. Count the number of programming languages that were designed to make the programmer happy. You can do it, even if you count in binary. Like you, I am thankful that I get to spend most of my day immersed in this wonder-world.
But do you sometimes wonder about what else is out there? If you don't, you should. It helps you get a perspective and be glad for what you have; at the same time you look forward and aspire for more.
In this talk, in all of 25-30 minutes, we will explore some ideas and patterns that can make our favorite programming language even better. Some of these ideas are already part of new releases of Ruby, some are baking while some are sadly, out of reach (for now).

Transcript

6. TAIL CALL OPTIMZATION
7. TCO def bar(n) foo(n-1) end def foo(n) raise "boom" if n <= 7 bar(n - 1) end
8. TCO foo(15)
9. TCO tail_rec.rb:8:in `foo': boom (RuntimeError) from tail_rec.rb:4:in `bar' from tail_rec.rb:9:in `foo' from tail_rec.rb:4:in `bar' from tail_rec.rb:9:in `foo' from tail_rec.rb:4:in `bar' from tail_rec.rb:9:in `foo' from tail_rec.rb:4:in `bar' from tail_rec.rb:9:in `foo' from tail_rec.rb:12:in `<main>'
10. TCO <compiled>:2:in 'foo': boom (RuntimeError) from tail_rec.rb:25:in 'eval' from tail_rec.rb:25:in '<main>'
11. TCO def foo(x) # do some other things 9 + bar(x) end
12. TCO def foo(x) # do some other things bar(9 + x) end
13. TCO BACK IN THE DAYS OF... ▸ CommonLisp ▸ Scheme ▸ ...
14. TCO IN SCALA @tailrec
15. TCO IN CLOJURE loop/let/recur
16. FIBONNACCI def fib(n) n.zero? ? 1 : (n * fib(n-1)) end
17. FIBONNACCI n * fib(n-1)
18. FIBONNACCI SystemStackError: stack level too deep
19. FIBONNACCI def fib(n, acc=1) n.zero? ? acc : fib(n-1, n*acc) end
20. FIBONNACCI fib(n-1, n*acc)
21. FIBONNACCI SystemStackError: stack level too deep
22. FIBONNACCI RubyVM::InstructionSequence.compile_option = { :tailcall_optimization => true, :trace_instruction => false }
23. FIBONNACCI source = <<-SOURCE def fib(n, acc=1) n.zero? ? acc : fib(n-1, n*acc) end puts fib(20_000) SOURCE
24. FIBONNACCI iseq = RubyVM::InstructionSequence.new(source) iseq.eval
25. PATTERN MATCHING
26. IN RUBY a, b, c, d = [1, 200, 32, 65.45] first, *rest = [1, 200, 32, 65.45] def foo(a: 1, b: 2); end
27. RUBY: splat/slurp def stats(*nums) [nums.min, nums.max] end stats(1,2,3,-100,100_0000)
28. RUBY: splat/split def add(a,b) a + b end add(*[1, 300])
29. IN RUBY dogs = { snowy: 'fox terrier', laika: 'mongrel' } dogs.each do |name, breed| puts "#{name} was a #{breed}" end
30. IN CLOJURE (def things [1 200 32 65.45]) (let [[a b c d] things] ( + a d)) ;; 64
31. IN ELIXIR defmodule MyNums def sum([]) do 0 end def sum([hd|tl]) do hd + sum(tl) end end MyNums.sum([1,2,3,4,5)] # 15
32. IN CLOJURE (defn sum [[x & xs]] (if (seq xs) (+ x (sum xs)) x)) (sum [1 2 3 4 5]) ;; 15
33. IN RUBY def sum(head, *tail) tail.empty? ? head : head + sum(*tail) end sum(1,2,3,4,5) # 15
34. BUT... IN ELIXIR iex> a = 1 1 iex> 1 = a 1
35. BUT... IN ELIXIR iex> 2 = a (MatchError) no match of right hand side value: 1
36. DESTRUCTURING IS EVERYWHERE
37. DESTRUCTURING MAPS (def div-attrs {:id "table-123" :css-class "table highlight"}) (let [{i :id c :css-class} div-attrs] (str "<div id='" i "' class='" c "'></div>")) ;; "<div id='table-123' class='table highlight'></div>"
38. DESTRUCTURING MAPS (let [:keys {id css-class} div-attrs] ;; use id and css-class )
39. DEEP DESTRUCTURING (def m {:a 5 :b 6 :c [7 8 9] :d {:e 10 :f 11}}) (let [{a :a b :b {e :e} :d} m] (+ a b e)) ;; 21
40. DEEP DESTRUCTURING (def famous-dogs [["snowy" 1929 :breed "fox terrier" :location "Belgium"] ["laika" 1954 :breed "mongrel" :location "USSR"]])
41. DEEP DESTRUCTURING [x & xs] matches a list or a vector
42. DEEP DESTRUCTURING [dog & more-dogs] matches famous-dogs
43. DEEP DESTRUCTURING Each dog is like: ["snowy" 1929 :breed "fox terrier" :location "Belgium"] ▸ [name year & more] matches a dog
44. DEEP DESTRUCTURING At this point, more is like: [:breed "fox terrier" :location "Belgium"] (apply hash-map more) is matched to {:keys [breed location]}
45. DEEP DESTRUCTURING (seq more-dogs) and (recur more-dogs)
46. DEEP DESTRUCTURING (loop [[[name year & {:keys [breed location]}] & more-dogs] famous-dogs] (prn (format "%s is a %s, born in %d in %s." name breed year location)) (if (seq more-dogs) (recur more-dogs))) ;; snowy is a fox terrier, born in 1929 in Belgium. ;; laika is a mongrel, born in 1954 in USSR.
47. IN RUBY'S FUTURE? Feature Request #8895 https://bugs.ruby-lang.org/issues/8895 params = {name: "John Smith", age: 42} {name: name, age: age} = params
49. HIGHER ORDER FUNCTIONS
50. HOFS IN RUBY? drinks.map { |d| d.gulp! } add = lambda { |a,b| a + b } add.call(1,3) # => 4
51. HOFS IN RUBY? m = 1.method(:+) # => #<Method: Fixnum#+>
52. HOFS IN RUBY? m.class.name # => Method m.methods.size # => 66
53. HOFS IN RUBY? But they are not first class: drinks.map(gulp!) # nope drinks.map { |d| d.gulp! } # yep
54. CURRYING
55. CURRYING (* 5 2) ; 10
56. CURRYING (* 5 2) ; 10 (partial * 5) ; #<core$partial$fn__4228 ...>
57. CURRYING Clojure's map function: (map fn collection)
58. CURRYING (map (fn [n] * 5 n) [1 2 3 4 5]) ; (5 10 15 20 25)
59. CURRYING (map (partial * 5) [1 2 3 4 5]) ; (5 10 15 20 25)
60. CURRYING RUBY? mult = lambda { |a,b| a * b } # => #<Proc ...> times_five = mult.curry[5] # => #<Proc ...>
61. CURRYING RUBY? times_five[10] # => 50 [1,2,3,4,5].map(&times_five) # => [5, 10, 15, 20, 25]
62. COMPOSITION def present?(word) ! blank?(word) end words.select { |w| present?(w) }
63. COMPOSITION select => filter filter fn collection
64. COMPOSITION (defn present? [str] (not (blank? str))) (filter present? words)
65. COMPOSITION (filter #(not (blank? %1)) words)
66. COMPOSITION (filter (comp not blank?) words)
67. HOFS In the real world: ring
68. HOFS rack == ring
69. HOFS rack == ring request/response: simple data structures
70. HOFS rack == ring request/response: simple data structures middleware are just functions
71. HOFS: RACK MIDDLEWARE class ResponseTimer def initialize # ... end def call # ... end end config.middleware.use "ResponseTimer"
72. HOFS: RING MIDDLWARE (wrap-ssl-redirect (wrap-not-modified (wrap-request-logging (wrap-token-authentication (wrap-params app)))))
73. HOFS: RING MIDDLEWARE (defn wrap-ssl-redirect [handler & ...] (fn [request] (if (= (:scheme request) :https) (handler request) (-> (resp/redirect ... ) (resp/status ...)))))
74. CONCURRENCY
75. HIGHER LEVEL ABSTRACTIONS ▸ Elixir: actors/processes & OTP ▸ Clojure: atoms/agents/refs & STM ▸ Go: channels and goroutines (core.async in Clojure)
76. DEEPER INTO CONCURRENCY AND RUBY... RuLu: http://v.gd/X0A1HQ RubyConf AU: http://v.gd/XYFA1b
77. I would remove the thread and add actors or some other more advanced concurrency features — Matz
78. IN RUBY: CELLULOID class Player include Celluloid def serve; end end djoker = Player.new djoker.async.serve Player.supervise_as(:djoker, "Djokovic") Celluloid::Actor[:djoker].async.serve
79. ELIXIR/ERLANG PROCESSES Processes are very very light-weight
80. ELIXIR/ERLANG PROCESSES Processes are very very light-weight fault-tolerance: let it crash
81. ELIXIR/ERLANG PROCESSES Processes are very very light-weight fault-tolerance: let it crash OTP framework + Elixir's dynamic nature
82. ELIXIR/ERLANG PROCESSES Processes are very very light-weight fault-tolerance: let it crash OTP framework + Elixir's dynamic nature Distributed
83. KEEP Experimenting!!
84. ध"यवाद