From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-08-03T04:51:45+09:00
Subject: Re: enum collection of constant values

On Wed, 3 Aug 2005, Patrick Hurley wrote:

> On 8/2/05, Ara.T.Howard <Ara.T.Howard@noaa.gov> wrote:
>> On Wed, 3 Aug 2005, Garance A Drosehn wrote:
>>> I'd like to have a set of constants for a class, where their values
>>> need to be unique, and preferably compact.  For instance:
>> class methods are your friend
>>
>> snip nice Enum module
>
> I like the Enum module, but if I include it into the 'main' scope, I need to
>
> self.class.enum to make it work. A bit more brute force, but works
> "automatically" in all contexts would be overloading Object. This then
> requires a smarter method of setting the const based upon where it is
> called from.
>
> class Object
>
>  def const_setter
>    set = if self.respond_to? :const_set
>      lambda { |sym, val| self.const_set sym.to_s.intern, val }
>    elsif self.class.respond_to? :const_set
>      lambda { |sym, val| self.class.const_set sym.to_s.intern, val }
>    else
>      # I don't think this code would ever get called...
>      lambda { |sym, val| eval "#{sym} = #{val}" }
>    end
>  end
>
>  def enum(*syms)
>    set = const_setter
>    syms.each_with_index do |sym,index|
>      set.call sym, index
>    end
>  end
>
>  def binary_enum(*syms)
>    set = const_setter
>    syms.each_with_index do |sym,index|
>      set.call sym, 2 ** index
>    end
>  end
>
> end

hmm.  this is a bit shorter


   harp:~ > cat a.rb
   class Object
     def enum(*list)
       mc = Module === self ? self : self.class
       list.flatten.each_with_index{|e, i| mc.const_set e.to_s.intern, i}
     end
     def bit_enum(*list)
       mc = Module === self ? self : self.class
       list.flatten.each_with_index{|e, i| mc.const_set e.to_s.intern,  2 ** i}
     end
   end

   class C
     enum %w(
       FOO
       BAR
       FOOBAR
       BARFOO
     )
   end

   class B
     bit_enum %w(
       FOO
       BAR
       FOOBAR
       BARFOO
     )
   end

   enum %w(
     FOO
     BAR
   )

   bit_enum %w(
     FOOBAR
     BARFOO
   )

   p C::FOO
   p C::BARFOO
   printf "0b%8.8b\n", B::FOO
   printf "0b%8.8b\n", B::BARFOO

   p FOO
   p BAR
   printf "0b%8.8b\n", FOOBAR
   printf "0b%8.8b\n", BARFOO



   harp:~ > ruby a.rb
   0
   3
   0b00000001
   0b00001000
   0
   1
   0b00000001
   0b00000010


probably could also combine this idea with the Enum module...

nice mod btw.

-a
-- 
===============================================================================
| email :: ara [dot] t [dot] howard [at] noaa [dot] gov
| phone :: 303.497.6469
| My religion is very simple.  My religion is kindness.
| --Tenzin Gyatso
===============================================================================