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From: stt@houdini.camb.inmet.com (Tucker Taft)
Subject: Re: [Technical] Generic child parameterised with instance of parent
Date: 1998/11/29
Message-ID: <F36vnM.KwF.0.-s@inmet.camb.inmet.com>#1/1
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References: <365D6AFE.D3BEE7D1@elca-matrix.ch>
Organization: Intermetrics, Inc.
Newsgroups: comp.lang.ada
Date: 1998-11-29T00:00:00+00:00
List-Id: <comp.lang.ada>

Mats Weber (Mats.Weber@elca-matrix.ch) wrote:

: Michel Gauthier wrote:

: > Here is the need as I can identify it (possibly not in a right way).

: > Then can be compiled. But the compiler rejects
: >     package InstChild is new P1Some . Child ( P1Other ) ;

: GNAT 3.11b accepts this, and does not need the G1bis declaration, so it
: does not seem to take G1 as denoting the current instance within the
: generic formal part of G1.Child. I don't know if that is right or not.

This sounds like a bug.  Everywhere inside the declarative region
of G1, G1 denotes the "current instance."

: Here is the exact code that I compiled:

: with G1.Child;

: procedure Gauthier_Generic_Child is

:    type Some_Type is new Integer;
:    type Other_Type is new Float;

:    package P1_Some is new G1 ( some_type ) ;
:    package P1_Other is new G1 ( other_type ) ;

:    package InstChild is new P1_Some . Child ( P1_Other ) ;

: begin
:    null;
: end;
: ---
: generic
:    with package GP is new G1 ( <> ) ;

   This is definitely wrong; G1 is not a generic inside G1.

: package G1 . Child is
: end;
: ---
: generic
:    type ITEM is private;
: package G1 is
: end G1;

I might add that, inside a child of G1, you don't normally need to
pass in an instance of G1, because an instance of G1 must
be specified as a prefix when instantiating the child, and that instance
can be referenced inside the child by simply using the name "G1."

If you need *two* instances of the parent generic inside the child, then 
you probably do need to do the generic renaming trick.

--
-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Burlington, MA  USA
An AverStar Company