From: Leslie Viljoen <leslie@...>
Date: 2005-11-24T05:31:33+09:00
Subject: Re: How does this work?

Gavin Kistner wrote:

> On Nov 23, 2005, at 10:42 AM, Graham wrote:
>
>> I cam across a construct in the FXRuby examples which I've not seen
>> before..
>> ..... lots of constants..(about 47 in total I believe)
>>   ID_INSERT_FILE,
>>   ID_EXTRACT_FILE,
>>   ID_WHEELADJUST,
>>   ID_LAST = enum(FXMainWindow::ID_LAST, 47)
>>
>> and I'm assuming this generates a unique number for each piece of  text,
>> which is subsequently used in the rest of the code. How does it work?
>
>
> Just a guess:
>
> def enum( start, count )
>   (start...start+count).to_a
> end
>
> a,b,c = enum( 101, 3 )
> p a,b,c
> #=> 101
> #=> 102
> #=> 103
>
>
> Except it looks like it's using the last value to update a constant  
> for future calls:
>
> LAST_ID = 101
> def enum( start, count )
>   return (start...start+count).to_a
> end
>
> a,b,c,LAST_ID = enum( LAST_ID, 4 )
> p a,b,c
> #=> 101
> #=> 102
> #=> 103
>
> d,e,f,g,LAST_ID = enum( LAST_ID, 5 )
> p d,e,f,g
> #=> 104
> #=> 105
> #=> 106
> #=> 107
>
>
> Note that the above (properly) generates warnings each time you  
> reassign to the global value. IMO a proper 'enum' solution would keep  
> track of that value internally.
>
>
Like so?:

#!/usr/bin/env ruby

module Enum
  @@last = 0
  def enum(n)
    r = (@@last..(@@last+n-1)).to_a
    @@last += n
    r
  end
end

include Enum

ROBO_LTHRUST,
ROBO_RTHRUST,
ROBO_FIRE = enum(3)

p ROBO_LTHRUST, ROBO_RTHRUST, ROBO_FIRE