Enumerable's Ugly Cousin - GORUCO Microtalk

A condensed, "highlights" version of the longer talk I gave at Ancient City Ruby Conf.

Transcript

1. Enumerator Enumerable’s Ugly Cousin @rossta GORUCO X
2. What we say about Enumerable
3. What we say about Enumerator
5. PRACTICAL EXPRESSIVE CLEAN ELEGANT MINASWAN READABLE SIMPLE SIMPLE HAPPINESS BEAUTIFUL CONCISE
8. You are all wrong, it’s also illegal
10. 2008 Rails 2 Ruby 1.8.7
12. What’s the estimate? Oh, about 4 days
13. 4 days weeks
14. How to model infinite, enumerable, recurring events?
15. { every: :month, on: { tuesday: 2 } }
16. Enumerator!
17. Enumerator – Ruby Docs “A class which allows both internal and external iteration.”
18. enum = [1, 2, 3].to_enum # => #<Enumerator: [1, 2, 3]:each> enum.next # => 1 enum.next # => 2 enum.next # => 3 enum.next # => StopIteration enum.each { |x| # ... }
19. “Ok, so what?”
20. Enumerators can be generators
21. $ rails g scaffold
23. Generators produce data on the fly
24. async infinite sequences fetching data list comprehensions concurrency lazy evaluation coroutines
25. JavaScript Generators in
27. –AirBnB JavaScript Style Guide “Don't use generators.”
32. Python Generators in
33. Awesome Simple, expressive. Love them. List comprehensions… insanely readable and easy to maintain
34. Generators let us be lazy
35. def fibonacci(n): result = [] a = b = 1 for i in xrange(n): result.append(a) a, b = b, a + b return result for a in fibonacci(20): print a def fibonacci(n): def fibonacci(n): result = [] def fibonacci(n): result = [] a = b = 1 for i in xrange(n): result.append(a) a, b = b, a + b return result def fibonacci(n): result = [] a = b = 1 for i in xrange(n): def fibonacci(n): result = [] a = b = 1 for i in xrange(n): result.append(a) a, b = b, a + b
36. result = [] result.append(a) return result def fibonacci(n): a = b = 1 for i in xrange(n): a, b = b, a + b for a in fibonacci(20): print a Eager!
37. yield a def fibonacci(n): a = b = 1 for i in xrange(n): a, b = b, a + b for a in fibonacci(20): print a Lazy!
38. Can we write generators in Ruby?* *yes, we can! Q:
39. def fibonacci(n): a = b = 1 for i in xrange(n): yield a a, b = b, a + b for a in fibonacci(20): print a
40. def fibonacci(n) a = b = 1 n.times do yield a a, b = b, a + b end end fibonacci(20) { |a| puts a } Not Enumerable!
41. Enumeratorize it!
42. def fibonacci(n) a = b = 1 n.times do yield a a, b = b, a + b end end def fibonacci(n) a = b = 1 n.times do yield a a, b = b, a + b end end return to_enum(__method__, n) unless block_given?
43. return to_enum(__method__) unless block_given? This seems like a big hack Too magical That’s ugly
44. def fibonacci(n) a = b = 1 n.times do yield a a, b = b, a + b end end def fibonacci(n) a = b = 1 n.times do yield a a, b = b, a + b end end return to_enum(__method__, n) unless block_given? ] [ Enumerable!
45. fibonacci(25).each { |a| puts a } fibonacci(25).map { |a| a * 3 }.select(&:odd?) fibonacci(100).find { |a| a > 50 }.take(5)
46. obj_to_enum(int argc, VALUE *argv, VALUE obj) { VALUE enumerator, meth = sym_each; if (argc > 0) { --argc; meth = *argv++; } enumerator = rb_enumeratorize_with_size(obj, meth, argc, argv, 0); if (rb_block_given_p()) { enumerator_ptr(enumerator)->size = rb_block_proc(); } return enumerator; } static VALUE enumerator.c
47. obj_to_enum(int argc, VALUE *argv, VALUE obj) { VALUE enumerator, meth = sym_each; if (argc > 0) { --argc; meth = *argv++; } enumerator = rb_enumeratorize_with_size(obj, meth, argc, argv, 0); if (rb_block_given_p()) { enumerator_ptr(enumerator)->size = rb_block_proc(); } return enumerator; } rb_enumeratorize_with_size(obj, meth, static VALUE enumerator.c obj_to_enum
48. Enumerators can be streams
49. (1..Float::INFINITY). map { |n| n * 3 }. # => ? select(&:odd?). take(100_000). reduce(&:+) (1..Float::INFINITY)
50. (1..Float::INFINITY). lazy. map { |n| n * 3 }. select(&:odd?). take(100_000). reduce(&:+) # => 30000000000
51. lazy augments how data is processed in an enumerator chain
52. Eager Pipeline [] map select reduce
53. Lazy Pipeline [] map select reduce
54. Enumerators solve difficult problems
55. Generating infinite sequences Processing large files Streaming API clients
56. Recurring events
57. Recurrence Enumerator find next event yield stop or continue
58. $ gem install montrose github.com/rossta/montrose # recurring events in Ruby
59. Enumeratorize it!
62. Enumerator is ugly beautiful
64. Sometimes, ugly code can teach us something
65. @rossta rossta.net Ross Kaffenberger
66. Live the questions now. Perhaps then, someday far in the future, you will gradually, without even noticing it, live your way into the answer… - Rilke