From: Eric Hodel <drbrain@...7.net>
Date: 2003-02-04T07:18:29+09:00
Subject: Re: What is a tuple?


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Mark Wilson (mwilson13@cox.net) wrote:

>=20
> On Monday, February 3, 2003, at 04:35 PM, Bob X wrote:
>=20
> >[snip]
>=20
> >Tuples are immutable lists.
> >
> >"Tuples have many uses. For example: (x, y) coordinate pairs, employee
> >records from a database, etc. Tuples, like strings, are immutable: it=20
> >is not possible to assign to the individual items of a tuple (you can=20
> >simulate much of the same effect with slicing and concatenation,=20
> >though). It is also possible to create tuples which contain mutable=20
> >objects, such as lists."
> ><-- from Python docs
>=20
> Thank you for the prompt response.  Could one then implement a tuple in=
=20
> Ruby as follows:
>=20
> class Tuple
>=20
>         attr_reader :tuple
>=20
>         def initialize(*args)
>                 @tuple =3D *args
>         end
> end

no, that's not immutable, you need something more like this:

module Enumerable
  def deepfreeze
    self.each do |o|
      if o !=3D self then=20
        o.deepfreeze
      else
        o.freeze
      end
    end
    self.freeze
  end
end

class Object
  def deepfreeze
    self.freeze
  end
end

class Tuple < Array
  def initialize(*stuff)
    super()
    self.push(*stuff)
    self.deepfreeze
  end
end

(comes from here)
http://sourceforge.net/project/shownotes.php?group_id=3D50485&release_id=3D=
124575

--=20
Eric Hodel - drbrain@segment7.net - http://segment7.net
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