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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
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 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: Using Red-Black Trees
Date: Thu, 18 Nov 2010 08:08:00 +0100
Organization: Ada @ Home
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Date: 2010-11-18T08:08:00+01:00
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Le Thu, 18 Nov 2010 07:27:20 +0100, J-P. Rosen <rosen@adalog.fr> a =C3=A9=
crit:

> Le 18/11/2010 00:39, Yannick Duch=C3=AAne (Hibou57) a =C3=A9crit :
>> You can have only one at a time. If you select an implementation, you=

>> select it system-wide, and you cannot select one for that usage and
>> another for another usage in the same system.
>>
> If that's really what you want, there is an easy solution.
> Provide two packages with identical (or compatible enough for your
> purpose) specifications:
>
> package Binary_Tree is....
> package Linked_List is....
>
> Then declare at library level:
> with Binary_Tree;
> package My_Structure renames Binary_Tree;
>
> And then, use My_Structure all over the place. By changing two words i=
n
> one two-line file, you can switch your entire project to the other
> implementation.
I know that one, but this is a workaround, not a language support (the s=
o  =

called =E2=80=9Cstatic polymorphism=E2=80=9D). Formally speaking, you do=
 not have multiple  =

implementations of a single specification. The closest thing actually is=
  =

generic package. But that is not easy to do with generics: you will have=
  =

to give the generic instance all of its custom implementation via generi=
c  =

parameters (methods and others).


-- =

Si les chats miaulent et font autant de vocalises bizarres, c=E2=80=99es=
t pas pour  =

les chiens.

=E2=80=9CI am fluent in ASCII=E2=80=9D [Warren 2010]