Re: Bizarre Range behavior

On Aug 4, 2009, at 3:04 PM, Yossef Mendelssohn wrote:
> On Aug 4, 1:47 pm, Scott Briggs <[e-mail]> wrote:
>> Can someone please explain this behavior in ruby (1.8.6p111):
>>
>>>> ("2"..."8").to_a
>>
>> => ["2", "3", "4", "5", "6", "7"]>> ("2".."8").to_a
>>
>> => ["2", "3", "4", "5", "6", "7", "8"]>> ("2".."9").to_a
>>
>> => ["2", "3", "4", "5", "6", "7", "8", "9"]>> ("2".."10").to_a
>> => []
>>>> ("2".."11").to_a
>> => []
>>>> ("1".."11").to_a
>>
>> => ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11"]

Well, you need to think about String#succ when the Range endpoints are  
String.

>
>
> It gets better.
>
>>> ("100".."11").to_a
>    => ["100"]

Now, that one is odd. I'd have predicted a result of:
  => ["100", "101", "102", "103", "104", "105", "106", "107", "108",  
"109"]
on the basis of staring with "100" and applying #succ until the value  
was >"11" like this loop does:

a = []
v = "100"
loop do
   break if v > "11"
   a << v
   v = v.succ
end
p a

This loop produced the "right" result for "2".."11" (namely an empty  
array) so the actual result defies (my) explanation.

>
> It seems you're running not so much into strange Range behavior as
> strange String behavior in certain numeric circumstances. Or maybe a
> combination of strange Range and String behvior. If you want the
> ranges to make more sense, use actual numbers.
>
>>> (2..11).to_a
>    => [2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
>
> If you want strings in the result, you can get that with a little bit
> of work.
>
>>> (2..11).to_a.map { |x|  x.to_s }
>    => ["2", "3", "4", "5", "6", "7", "8", "9", "10", "11"]
>
> --
> -yossef



Of course, you can also do things like:

("a".."ah").to_a
=> ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m",  
"n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "aa",  
"ab", "ac", "ad", "ae", "af", "ag", "ah"]

Which might help label your spreadsheet columns.

-Rob

Rob Biedenharn		http://agileconsultingllc.com
[e-mail]