Gluttonous

('1'..'10').to_a
# => ["1", "2", "3", "4", ..... "10"]

('2'..'10').to_a
# => []

('2'..'20').to_a
# => ["2", "3", "4", "5", ..... "20"]

('3'..'20').to_a
# => []

('3'..'30').to_a
# => ["3", "4", "5", "6", ..... "30"]

('4'..'30').to_a
# => []

('4'..'40').to_a
# => ["4", "5", "6", "7", ..... "40"]

(2..10).to_a
# => [2, 3, 4, 5, 6, 7, 8, 9, 10]

('2'.to_i .. '10'.to_i).to_a
# => [2, 3, 4, 5, 6, 7, 8, 9, 10]

Posted in Musings, Ruby | 5 comments

Comments

1. nukeedit
   Matthew Conway said about 1 hour later:
   

   Interesting – took me a while to figure it out :)

   • spoiler *

   I wouldn’t call it a bug though – ‘2’ is > ‘10’ i.e. strings don’t sort like numbers

2. nukeedit
   Dr J said about 2 hours later:
   

   Very good find…

3. nukeedit
   Kevin Clark said about 7 hours later:
   

   Ok, whether this is a bug or not is certainly up for interpretation, but it’s an interesting gotcha either way.

4. nukeedit
   Jean-Philippe Bougie said about 9 hours later:
   

   String#succ, which is used by the the range is quite a strange beast, especially since its rules do not conform well to String#<=>. succ has special treatment of carry with characters and numbers, and doesn’t follow the normal ascii set. For example, ‘9’.succ is ‘10’, ‘z’.succ is ‘aa’, but ’ ?’.succ is ’@’. On the other hand, <=> goes character by character. So yes, it is definitely a gotcha, but stranger things do happen with ranges :

   (‘a ’..’b’).include? ‘a ’ => true (‘a ’..’b’).include? ‘b’ => true (‘a ’..’b’).to_a => [‘a ‘] # where is ‘b’?

5. nukeedit
   Jean-Philippe Bougie said about 9 hours later:
   

   oops, those small examples got mangled

   (‘a ’..’b’).include? ‘a ’ => true

   (‘a ’..’b’).include? ‘b’ => true

   (‘a ’..’b’).to_a => [‘a ‘] # where is ‘b’?

   In the end, one has to be careful using string ranges with Range#to_a, as it can give strange results even with alphabetic characters only :

   (‘A’..’b’).include? ‘a’ => true

   (‘A’..’b’).to_a.include? ‘a’ => false

   (‘A’..’b’).to_a => [‘A’, ‘B’, ‘C’, ... ‘Z’]

   ‘Z’.succ gives ‘AA’, which is greater than ‘a’, thus #to_a stops at that point

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