From: Rob <Rob@...>
Date: 2006-03-08T11:13:42+09:00
Subject: Re: Indexing system - ruby newbie

On 2006-03-03, Malte Milatz <malteNOSPAM@gmx-topmail.de> wrote:
>
>
> Adam Groves schrieb:
>> I'm trying to write a class which converts a number into letters like 
>> so:
>> 0  => -
>> 1  => A
>> 10 => J
>> 27 => AA
>
> Only after reading the other posts, I realized you want Y, Z, AA, AB, AC
> and not Y, Z, AA, BB, CC, which is what is produced by this:
>
> def letter(i)
>   return '-' if i < 1
>   ('A'..'Z').to_a.at(i%26 - 1) * ((i-1)/26 + 1)
> end
>
> Malte

could add one method  to Integer
and avoid a separate class.
(_to_aa is a helper that works on
0..25 nstead of 1..26)

eg
puts 10.to_aa, (10**1000).to_aa

class Integer

	def to_aa # (1..26) to (A..Z)
	  if (self < 1)
	    	'-'
    else
      (self-1)._to_aa
	  end
	end

  protected
  def _to_aa # helper (0..25) to (A..Z)
	  if  (self < 26)
	  	(self+?A).chr
	  else
		  ((self/26)-1)._to_aa+(self%26)._to_aa
	  end
  end

end