From: Robert Dober <robert.dober@...>
Date: 2006-07-28T18:33:36+09:00
Subject: Re: Creating hashes with duplicate keys

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On 7/28/06, Sy Ali <sy1234@gmail.com> wrote:
>
> I want to simplify this hash creation:
> g =3D { 1 =3D> "test", 2 =3D> "test", }
>
> I have a particularly complicated hash that I'm generating.  It can
> have very large values.
>
> Right now, I duplicate values with something like this:
>
> c =3D { 1 =3D> "one", }
> d =3D { 2 =3D> c[1], }
> c.merge!(d)
>
> however, I don't like the way my code looks.. I want to be able to
> specify the duplication within the hash generation.
>
> Is this possible?
>
> Hmm I am not completely sure what you want achieve.

In the following implementations there are two possible Approaches, the
class YourHash
implements domaindependent key duplication. Iow YourHash is a mapping from
one Domain to another and both are distinct, thus if the mapping value is i=
n
the mapped Domain it is just replaced by the mapping value. Ahem that does
not read well.
I mean:
Keys and values are distinct and thus if a value is already a key it is
replaced by its value.

The second approach is to monkeypatch Hash to add a duplicate method,
allowing you
to define as many "synonyms" or "aliases" for one key.

Hope that helps

Robert
------------------------------------------------- 8<
--------------------------------------
521/21 > cat hash.rb && ./hash.rb
#!/usr/bin/env ruby
#
#

class YourHash < Hash
        def []=3D(key, value)
                if has_key?( value ) then
                        super(key, self[value])
                else
                        super(key, value)
                end
        end
end

class Hash
        def duplicate(key, *tokeys)
                value =3D self[key]
                tokeys.each do
                        |new_key|
                        self[new_key] =3D value
                end
        end
end

h =3D YourHash.new
h[:a]=3D1
h[:b]=3D:a

p h

h =3D Hash.new
h[:a]=3D1
h.duplicate( :a, :b, :c )
p h
--------------> OUTPUT <------------------
{:a=3D>1, :b=3D>1}
{:c=3D>1, :a=3D>1, :b=3D>1}


--=20
Deux choses sont infinies : l'univers et la b=EAtise humaine ; en ce qui
concerne l'univers, je n'en ai pas acquis la certitude absolue.

- Albert Einstein

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