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  1. # Swift's closure
  2. #   https://d...content-available-to-author-only...e.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html
  3.  
  4.  
  5. class String
  6.     class << self
  7.         def __unfoldl_rec__(b, &block)
  8.             return self.to_enum(:__unfoldl_rec__, b) unless block_given?
  9.  
  10.             if (pair = yield b).nil?
  11.                 ''
  12.             else
  13.                 a, b1 = pair
  14.  
  15.                 __unfoldl_rec__(b1, &block) + a
  16.             end
  17.         end
  18.  
  19.  
  20.         def __unfoldl_until__(b)
  21.             return self.to_enum(:__unfoldl_until__, b) unless block_given?
  22.  
  23.             s  = ''
  24.             until (pair = yield b).nil?
  25.                 a, b = pair
  26.  
  27.                 s += a
  28.             end
  29.  
  30.             s
  31.         end
  32.  
  33.  
  34.         def __unfoldl_loop__(b)
  35.             return self.to_enum(:__unfoldl_loop__, b) unless block_given?
  36.  
  37.             loop.inject([b, '']) { |(b1, s), _|
  38.                 if (pair = yield b1).nil?
  39.                     break s
  40.                 else
  41.                     a, b2 = pair
  42.  
  43.                     [b2, a + s]
  44.                 end
  45.             }
  46.         end
  47.  
  48.  
  49.         # alias unfoldl __unfoldl_rec__
  50.           alias unfoldl __unfoldl_until__
  51.         # alias unfoldl __unfoldl_loop__
  52.     end
  53. end
  54.  
  55.  
  56.  
  57. DigitNames = {
  58.     0 => "Zero", 1 => "One", 2 => "Two",   3 => "Three", 4 => "Four",
  59.     5 => "Five", 6 => "Six", 7 => "Seven", 8 => "Eight", 9 => "Nine"
  60. }
  61. Numbers = [16, 58, 510]
  62.  
  63.  
  64. puts '==== Internal enumerator ===='
  65. strings = Numbers.map { |number|
  66.     String.unfoldl(number) { |num|
  67.         if num <= 0
  68.             nil
  69.         else
  70.             [DigitNames[num % 10], num / 10]
  71.         end
  72.     }
  73. }
  74.  
  75. for s in strings
  76.     puts s
  77. end
  78.  
  79.  
  80. puts
  81. puts '==== External enumerator (aka. Generator) ===='
  82. strings = Numbers.map { |number|
  83.     for num in String.unfoldl(number)
  84.         if num <= 0
  85.             nil
  86.         else
  87.             [DigitNames[num % 10], num / 10]
  88.         end
  89.     end
  90. }
  91.  
  92. for s in strings
  93.     puts s
  94. end
Success #stdin #stdout 0.02s 7432KB
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==== Internal enumerator ====
SixOne
EightFive
ZeroOneFive

==== External enumerator (aka. Generator) ====
SixOne
EightFive
ZeroOneFive
https://ideone.com/9x6s0h
language:
Ruby (ruby 2.5.5)
created:
11 years ago
visibility:
public

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