From: Garance A Drosehn <drosihn@...>
Date: 2006-03-19T09:01:57+09:00
Subject: Re: c/c++ enum equivalent?

On 3/17/06, benjohn@fysh.org <benjohn@fysh.org> wrote:
>
> I'd like to fill a module with valueless constants (because I don't care
> about the actual values, just that they are unique, and named)

# -------+---------+---------+-------- + --------+---------+---------+---------+
#   Add methods enum and bit_enum to the Object class, thus making it much
#   easier and less error-prone to define a long list of constants in a
#   class.  This idea comes from Ara.T.Howard@noaa, in a posting to ruby-talk
#   on August 2, 2005 (in reply to a question).  These work very nicely with
#   a word-list array as generated via %w().  Very clever!
#
class Object
    def enum_constants(*list)
    mc = Module === self ? self : self.class
    list.flatten.each_with_index{|e, i| mc.const_set e.to_s.intern, i}
    end
    def enum_bit_constants(*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

# -------+---------+---------+-------- + --------+---------+---------+---------+

An example of use:

    #   Constants that define all categories of packets which we recognize.
    enum_constants %w(
	  SBC_NONE       SBC_ARRAY    SBC_GOODPW   SBC_GOODKEY  SBC_GOODNONE
	  SBC_BADPW      SBC_BADKEY   SBC_BADNONE  SBC_IGNFAIL  SBC_ALL
	  SBC_UNMATCHED
    )				#  "UNMATCHED" should be the last one.
    SBC_ENUMCOUNT = SBC_UNMATCHED + 1;

I've been meaning to add a few more bells and whistles to this,
such as having a way for 'enum_constants' to automatically
handle the definition of values such as SBC_ENUMCOUNT.
But of course I have a few million things that "I've been meaning
to do", and never get around to.

Someone else had a module of some sort for enums.  I forget
who, but it was someone on this mailing list in the last month
or so.  Their version was very different from the above, and it
in some situations what they did would have some significant
advantages over the simple solution I like to use.

--
Garance Alistair Drosehn     =             drosihn@gmail.com
Senior Systems Programmer               or   gad@FreeBSD.org
Rensselaer Polytechnic Institute;             Troy, NY;  USA