From: Patrick Hurley <phurley@...>
Date: 2005-08-03T01:57:00+09:00
Subject: Re: enum collection of constant values

Oops I had not read your whole message. To handle the binary one, I
think you would need to drop into some real code:

module Kernel

  def enum(*syms)
    index = 0
    puts self
    puts self.send(:binding)
    syms.each do |sym|
      eval "#{sym.to_s} = #{index}"
      index += 1
    end
  end

  def binary_enum(*syms)
    index = 1
    syms.each do |sym|
      eval "#{sym.to_s} = #{index}"
      index *= 2
    end
  end

end

enum :A, :B, :C
binary_enum :X, :Y, :Z

would work, but they will always be at the global context. In rite,
will we get a way to get the caller's binding? That would be very nice
to make this method more versatile.

pth

On 8/2/05, Patrick Hurley <phurley@gmail.com> wrote:
> Not quite perfect, but not too bad you can:
> 
>  SB_MODA, SB_MODB, SB_MODC = *0..2
> 
> If your range at the end "goes too far" there is no problem, but if it
> comes up short then some of your constants will silently not be
> initialized.
> 
> 
> 
> On 8/2/05, Garance A Drosehn <drosihn@gmail.com> 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:
> >    SB_NONE = 0; SB_GOOD = 1; SB_BAD = 2; SB_LOGIC_ERR = 3;
> >    SB_MAX = SB_LOGIC_ERR
> >
> > but if I want to modify this list by adding something in the middle,
> > then I have to remember to increment (by hand) all the values
> > which come after that new value.
> >
> > In C, I would do something like:
> >     typedef enum { SB_NONE, SB_GOOD, SB_BAD,
> >         SB_LOGICERR } sb_set;
> >
> > Looking through the pickaxe book, it looks like the closest thing
> > I can do is to create an array of words, and then use the indexes
> > of where those words are in the array.  But that isn't really the
> > same thing.   I'd like the efficiency of having constant values,
> > which would be referred to by name.
> >
> > (And after I have that for a compact set of values, I'd want a
> > similar feature which would give me a bit-wise unique set of
> > values.  Eg:  SB_MODA = 1; SB_MODB = 2; SB_MODC = 4;
> > SB_MODD = 8; -- such that I could combine the values together
> > using '|', and tell which values were 'or'-ed together to get that
> > combined value...)
> >
> > --
> > Garance Alistair Drosehn     =             drosihn@gmail.com
> > Senior Systems Programmer               or   gad@FreeBSD.org
> > Rensselaer Polytechnic Institute;             Troy, NY;  USA
> >
> >
>