From: Clemens Hintze <c.hintze@...>
Date: 2001-01-05T10:40:02+09:00
Subject: [ruby-talk:8659] Re: Any way to get enumerated values?

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>>>>> "Lyle" == Lyle Johnson <ljohnson@resgen.com> writes:

(...)

    Lyle> Ahhh, I didn't specify enough constraints on the problem ;)
    Lyle> And those would be that the constants are in fact integer
    Lyle> values; I need to be able to specify a specific starting
    Lyle> value for the sequence; and I want the values to be
    Lyle> generated sequentially so that I'm guaranteed that all the
    Lyle> values are greater than the starting value.

    Lyle> In other words, I need it to work exactly like C enums ;)

Hmmm ... in the beginning, erhm ... I mean: once upon a time ... no.
What I want to say is, that I had written such a module as experiment
some time ago! 

The trick is to create an anonymous module that contains constants
with the corresponding values. You catch the reference of that module
and put it into an variable. Then you may refer to a certain enum via
the module::Constant access syntax!

I have attached my module on that article. If you simply start it via

  ruby enumeration.rb

you will see some test output. I really *love* that language :-)))

(...)


HTH,
\cle


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#!/bin/env ruby


def Enumeration(*args)
  args << :sentinel    =

  mod =3D Module.new
  name, value =3D "", -1
  for arg in args
    unless name.empty?
      unless name[0].between?(?A, ?Z)
	raise SyntaxError, "Enumerator have to begin with [A-Z]: (#{name})",
	      caller[2..-1]
      end
      mod.module_eval "#{name} =3D #{value}"
    end
    if arg.type =3D=3D String
      name, value =3D arg, value + 1
    elsif arg.type =3D=3D Symbol
      name, value =3D arg.id2name, value + 1
    elsif arg.type <=3D Numeric
      mod.module_eval "remove_const :#{name}"
      value =3D arg
    else
      raise TypeError, "only String, Symbol or Numeric instances allowed"=
,
            caller[2..-1]
    end
  end
  mod
end


if __FILE__ =3D=3D $0
  # Gnark  =3D> 2
  # Blubb  =3D> 7
  # Foo    =3D> 8
  # Bar    =3D> 9
  # Foobar =3D> 10

  spam =3D Enumeration("Gnark",2, "Blubb",7, "Foo", :Bar, :Foobar)
  =

  print "Value of spam::Gnark =3D> ", spam::Gnark, "\n"
  print "Value of spam::Bar =3D> ", spam::Bar, "\n"

end

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