From: ara.t.howard@...
Date: 2005-12-14T02:58:06+09:00
Subject: Re: ,elegant

On Wed, 14 Dec 2005, Leslie Viljoen wrote:

> Hiya!
>
> This function adds commas to a string after every three characters
> so a number would be easier to read. It's kinda ugly though, and I can't
> help thinking there'd be a elegant Why-esque one or two liner to do
> this kind of thing - anyone care to improve it?
>
>
> def add_commas(str)
> return nil if str.class != String
>
> ret = ""
> len = str.length
> i = len - 1
> while i >= 0
>   ret = str[i].chr + ret
>   if ((len-i) % 3) == 0
>     ret = "," + ret
>   end
>   i -= 1
> end
> if ret[0].chr == ","
>   ret = ret[1..-1]
> end
> ret
> end

   harp:~ > cat a.rb
   def commafy s
     s.to_s.reverse.scan(%r/.{1,3}/).join(',').reverse
   end

   p(commafy(''))
   p(commafy('4'))
   p(commafy('42'))
   p(commafy('422'))
   p(commafy('4242'))
   p(commafy('42424'))
   p(commafy('424242'))
   p(commafy('4242424'))

   harp:~ > ruby a.rb
   ""
   "4"
   "42"
   "422"
   "4,242"
   "42,424"
   "424,242"
   "4,242,424"

if you want you can play with the pattern so the two reverses aren't needed...
but this is quicker to write ;-)

-a
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