Dissecting Ruby

Transcript

1. Dissecting a Ruby Block Pat Shaughnessy http://patshaughnessy.net BostonRB Sept. 11,

   2012

2. Why learn Ruby internals?

3. 10.times do |n| puts n end

4. None

5. Blocks: Closures in Ruby Closures and Metaprogramming

6. rb_block_t ??

7. Calling a block

8. 10.times do str = "The quick brown fox..." puts str

   end

9. rb_block_t iseq putstring "The quick brown fox… " setdynamic str,

   0 putself getdynamic str, 0 send :puts, 1 leave

10. Referencing variables from the parent scope

11. str = "The quick brown fox" 10.times do str2 =

    "jumps over the lazy dog." puts "#{str} #{str2}" end

12. str = "The quick brown fox"

13. YARV internal stack locals: str rb_control_frame_t LFP

14. str = "The quick brown fox" 10.times do ...

15. YARV internal stack locals: str rb_block_t iseq DFP rb_control_frame_t LFP

16. ... do str2 = "jumps over the lazy dog." puts

    "#{str} #{str2}" end

17. rb_block_t iseq DFP YARV internal stack locals: str locals: str2

    DFP rb_control_frame_t

18. rb_block_t iseq DFP putstring "jumps over the lazy dog." setdynamic

    str, 0 putself getdynamic str2, 1 tostring putstring " " getdynamic str, 0 tostring concatstrings 3 send :puts, 1, nil, 8, <ic:0> leave YARV internal stack locals: str
19. None

20. “In computer science, a closure (also lexical closure or function

    closure) is a function or reference to a function together with a referencing environment...” Sussman and Steele. Scheme: An interpreter for extended lambda calculus

21. Creating and calling a lambda

22. None

23. def display_message str = "The quick brown fox" lambda do

    str2 = "jumps over the lazy dog" puts "#{str} #{str2}" end end display_message.call

24. def display_message str = "The quick brown fox" ... end

25. YARV internal stack locals: str rb_control_frame_t LFP

26. str = "The quick brown fox" lambda do ... end

27. str rb_control_frame_t LFP rb_env_t env rb_proc_t rb_block_t iseq DFP envval

    is_lambda Stack Heap str

28. display_message.call

29. locals: str2 DFP rb_control_frame_t rb_env_t env rb_proc_t rb_block_t iseq DFP

    envval is_lambda Stack Heap str

30. def display_message str = "The quick brown fox" lambda do

    str2 = "jumps over the lazy dog" puts "#{str} #{str2}" end end display_message.call

31. Blocks: Closures in Ruby Closures and Metaprogramming

32. Using a closure to define a method

33. class Quote def initialize @str = "The quick brown fox..."

    end def display_message puts @str end end

34. class Quote def initialize @str = "The quick brown fox..."

    end define_method :display_message do puts @str end end

35. class Quote def initialize @str = "The quick brown fox"

    end end str2 = "jumps over the lazy dog." Quote.send(:define_method, :display_message) do puts "#{@str} #{str2}" end

36. eval and binding

37. str = "puts" str += " 2" str += "

    +" str += " 2" eval(str) => 4

38. class Quote def initialize @str = "The quick brown fox..."

    end def get_binding binding end end

39. obj = Quote.new

40. rb_control_frame_t LFP self RObject ivptr klass @str etc...

41. obj = Quote.new eval('puts @str', obj.get_binding)

42. rb_control_frame_t LFP self rb_binding_t filename line_no env rb_env_t rb_block_t iseq

    DFP env self Stack Heap RObject ivptr klass @str etc...

43. putstring "The quick brown fox… " setdynamic str, 0 putself

    getdynamic str, 0 send :puts, 1 leave YARV internal stack locals: str RObject ivptr klass rb_block_t DFP self iseq

44. instance_eval

45. class Quote def initialize @str = "The quick brown fox"

    end end

46. str2 = "jumps over the lazy dog." obj = Quote.new

    obj.instance_eval do puts "#{@str} #{str2}" end

47. instance_eval and singleton classes

48. class Quote def initialize @str = "The quick brown fox..."

    end end

49. obj = Quote.new obj.instance_eval do def display_message puts @str end

    end

50. obj.display_message The quick brown fox jumps over the lazy dog.

    Quote.new.display_message ...undefined method `display_message' for #<Quote:0x007fdf789504e8> (NoMethodError)

51. RClass super RClass super Object (class) Kernel (module) Quote (class)

    RClass super RClass super BasicObject (class) RObject klass obj (object)

52. etc... RClass super RClass super Object (class) obj (object) RObject

    klass SomeClass (class) RClass super #<Class:#<Quote:0x007f9ed9150c28>> (singleton)

53. http://patshaughnessy.net/ruby-under-a-microscope