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
   

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2. What we say about
   Enumerable
   

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3. What we say about
   Enumerator
   

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5. PRACTICAL
   EXPRESSIVE
   CLEAN
   ELEGANT
   MINASWAN
   READABLE
   SIMPLE
   SIMPLE
   HAPPINESS
   BEAUTIFUL
   CONCISE
   

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8. You are all wrong,
   it’s also illegal
   

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10. 2008
    Rails 2
    Ruby 1.8.7
    

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12. What’s the estimate?
    Oh, about 4 days
    

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13. 4 days
    weeks
    

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14. How to model
    infinite, enumerable,
    recurring events?
    

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15. { every: :month, on: { tuesday: 2 } }
    

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16. Enumerator!
    

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17. Enumerator
    – Ruby Docs
    “A class which allows
    both internal and
    external iteration.”
    

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18. enum = [1, 2, 3].to_enum
    # => #
    enum.next # => 1
    enum.next # => 2
    enum.next # => 3
    enum.next # => StopIteration
    enum.each { |x| # ... }
    

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19. “Ok, so what?”
    

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20. Enumerators can be
    generators
    

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21. $ rails g scaffold
    

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23. Generators
    produce
    data
    on the
    fly
    

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24. async
    infinite sequences
    fetching data
    list comprehensions
    concurrency
    lazy evaluation
    coroutines
    

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25. JavaScript
    Generators in
    

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27. –AirBnB JavaScript Style Guide
    “Don't use generators.”
    

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32. Python
    Generators in
    

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33. Awesome
    Simple, expressive.
    Love them.
    List comprehensions…
    insanely readable and
    easy to maintain
    

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34. Generators let us be
    lazy
    

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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
    

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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!
    

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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!
    

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38. Can we write
    generators in Ruby?*
    *yes, we can!
    Q:
    

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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
    

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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!
    

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41. Enumeratorize it!
    

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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?
    

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43. return to_enum(__method__) unless block_given?
    This seems like a big hack
    Too magical
    That’s ugly
    

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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!
    

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45. fibonacci(25).each { |a| puts a }
    fibonacci(25).map { |a| a * 3 }.select(&:odd?)
    fibonacci(100).find { |a| a > 50 }.take(5)
    

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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
    

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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
    

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48. Enumerators can be
    streams
    

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49. (1..Float::INFINITY).
    map { |n| n * 3 }. # => ?
    select(&:odd?).
    take(100_000).
    reduce(&:+)
    (1..Float::INFINITY)
    

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50. (1..Float::INFINITY).
    lazy.
    map { |n| n * 3 }.
    select(&:odd?).
    take(100_000).
    reduce(&:+)
    # => 30000000000
    

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51. lazy augments how
    data is processed in an
    enumerator chain
    

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52. Eager Pipeline
    [] map select reduce
    

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53. Lazy Pipeline
    [] map select reduce
    

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54. Enumerators
    solve difficult problems
    

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55. Generating infinite sequences
    Processing large files
    Streaming API clients
    

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56. Recurring events
    

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57. Recurrence
    Enumerator
    find next event
    yield
    stop or continue
    

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58. $ gem install montrose
    github.com/rossta/montrose
    # recurring events in Ruby
    

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59. Enumeratorize it!
    

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62. Enumerator is ugly
    beautiful
    

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64. Sometimes, ugly code can
    teach us something
    

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65. @rossta
    rossta.net
    Ross Kaffenberger
    

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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
    

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