package child question

package child question

[Georg Bauhaus]

Hello,
I wonder if someone could help me pointing out to me what I've done
wrong in the following two library hierarchies; the first has
a parent and a child, not withing anything, while the second
hierarchy's child body withes the child of the first, like this:

package A is
end A;

package A.B is
end A.B;


package B is
end B;

package B.A is
   pragma Elaborate_Body;
end B.A;

with A.B;
package body B.A is

begin
   declare
      use A.B;  -- compiler says: "B" not declared in "A"
   begin
      null;
   end;
end B.A;

This only happens if the use clause is in A.B body statements,
there is no error message when it is in the context clause of A.B.
Is there a way out of this, other than choosing different names
(which works)?


  Georg Bauhaus

Re: package child question

[Jean-Pierre Rosen]

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Georg Bauhaus <sb463ba@d250-hrz.uni-duisburg.de> a �crit dans le message :
87mugk$sa3$1@news-hrz.uni-duisburg.de...
> with A.B;
> package body B.A is
>
> begin
>    declare
>       use A.B;  -- compiler says: "B" not declared in "A"
>    begin
>       null;
>    end;
> end B.A;
>
> This only happens if the use clause is in A.B body statements,
> there is no error message when it is in the context clause of A.B.
> Is there a way out of this, other than choosing different names
> (which works)?
>
The closest 'A' that is visible is B.A, so you "use A.B" really means "use
B.A.B".
If you want to be absolutely, unambiguously sure of what you name, start
with Standard:
use Standard.A.B;

(unless you have also redefined locally Standard, but that would *really* be
looking for trouble :-)

--
---------------------------------------------------------
           J-P. Rosen (Rosen.Adalog@wanadoo.fr)
Visit Adalog's web site at http://pro.wanadoo.fr/adalog

package child question

[Christoph Grein]

Matthew Heaney has pointed out the cause of your problem.

Apart from renaming, another solution is possible. Remember that any library
unit is supposed to be a child of Standard, so you might write

with A.B;
package body B.A is  -- this A hides the imported one

begin
   declare
      use Standard.A.B;  -- qualification makes it accessible again
   begin
      null;
   end;
end B.A;

Re: package child question

[Matthew Heaney]

In article <87mugk$sa3$1@news-hrz.uni-duisburg.de> , 
sb463ba@d250-hrz.uni-duisburg.de (Georg Bauhaus) wrote:

> with A.B;
> package body B.A is
>
> begin
>    declare
>       use A.B;  -- compiler says: "B" not declared in "A"
>    begin
>       null;
>    end;
> end B.A;
>
> This only happens if the use clause is in A.B body statements,
> there is no error message when it is in the context clause of A.B.

A name always denotes the entity with the most inner scope.  In your
case, the name "A" denotes the package B.A, because that is the A-entity
declared in the most inner scope.

> Is there a way out of this, other than choosing different names
> (which works)?

You could try doing a library-level package renames:

-- this is its own file, say ab.ads
package AB renames A.B;

-- now with the renamed package:
with AB;
package body B.A is
begin
  declare
    use AB;
  begin
    null;
  end;
end B.A;

I haven't tried compiling this, though.


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Re: package child question

[Steve Folly]

Jean-Pierre Rosen <rosen.adalog@wanadoo.fr> wrote, among other things, in
message news:87oi6t$jd$1@wanadoo.fr...
>
> If you want to be absolutely, unambiguously sure of what you name, start
> with Standard:
> use Standard.A.B;
>
> (unless you have also redefined locally Standard, but that would *really*
be
> looking for trouble :-)
>

Just a minor point... as all packages are implicitly child packages of
Standard, you don't actually have to with Standard - just the use clause
will work.

We had a problem like this with some code at work...

package Icp_Button is
...
end Icp_Button;

package Icp_Button.Field is
...
end Icp_Button.Field;


package Field is
...
end Field;


Any reference to the package Field in Icp_Button.Field has to be qualified
with Standard.
OK, maybe the names of the packages were badly chosen, but we wont argue
about that....



--
Regards,
Steve Folly.
http://www.follysplace.demon.co.uk
donationsto:myaccount@mybank.co.uk

Re: package child question

[Georg Bauhaus]

Thank you for all the answers!
Matthew Heaney's renaming solution worked (well, of course?)
when prefixed with A.B;

 Georg Bauhaus

Re: package child question

[Robert A Duff]

"Jean-Pierre Rosen" <rosen.adalog@wanadoo.fr> writes:

> A funny and unfortunate effect of automatic lines folding!
> I wrote "start with Standard", I didn't suggest to have a "with standard;".

Well, *I* understood what you said.  Besides, "with" is not a verb in
English.  Why did JDI choose it, instead of, say, "use" or "import"?
The RM says "mention in a with clause", but that's too long, so people
say "to with, or not to with".  ;-)

- Bob

Re: package child question

[Jean-Pierre Rosen]

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Steve Folly <steve@follysplace.demon.co.uk> a �crit dans le message :
950043074.13382.0.nnrp-08.c2de848f@news.demon.co.uk...
>
> Jean-Pierre Rosen <rosen.adalog@wanadoo.fr> wrote, among other things, in
> message news:87oi6t$jd$1@wanadoo.fr...
> >
> > If you want to be absolutely, unambiguously sure of what you name, start
> > with Standard:
> > use Standard.A.B;
> >
> > (unless you have also redefined locally Standard, but that would
*really*
> be
> > looking for trouble :-)
> >
>
> Just a minor point... as all packages are implicitly child packages of
> Standard, you don't actually have to with Standard - just the use clause
> will work.
>
A funny and unfortunate effect of automatic lines folding!
I wrote "start with Standard", I didn't suggest to have a "with standard;".
As an evidence of my innocence, notice that the word "Standard" is followed
by a colon, not a semi-colon :-)

--
---------------------------------------------------------
           J-P. Rosen (Rosen.Adalog@wanadoo.fr)
Visit Adalog's web site at http://pro.wanadoo.fr/adalog

Re: package child question

[Marin D. Condic]

Ehud Lamm wrote:
> 
> On Wed, 9 Feb 2000, Robert A Duff wrote:
> 
> |The RM says "mention in a with clause", but that's too long, so people
> |say "to with, or not to with".  ;-)
> |
> 
> But "to use, or not to use" - that is the question!
> 
Or how about "instantiate" or "instantiation"? Ada has definitely
twisted a few English language words around. One wonders if Gen.
Alexander Haig was consulted on any of this, seeing as he was famous for
turning nouns into verbs, etc.

MDC
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Re: package child question

[Ehud Lamm]

On Wed, 9 Feb 2000, Robert A Duff wrote:

|The RM says "mention in a with clause", but that's too long, so people
|say "to with, or not to with".  ;-)
|

But "to use, or not to use" - that is the question!

Ehud Lamm mslamm@mscc.huji.ac.il
http://purl.oclc.org/NET/ehudlamm <== My home on the web 
Check it out and subscribe to the E-List- for interesting essays and more!

Re: package child question

[Larry Kilgallen]

In article <38A20732.F8119EBB@quadruscorp.com>, "Marin D. Condic" <mcondic-nospam@quadruscorp.com> writes:
> Ehud Lamm wrote:
>> 
>> On Wed, 9 Feb 2000, Robert A Duff wrote:
>> 
>> |The RM says "mention in a with clause", but that's too long, so people
>> |say "to with, or not to with".  ;-)
>> |
>> 
>> But "to use, or not to use" - that is the question!
>> 
> Or how about "instantiate" or "instantiation"? Ada has definitely
> twisted a few English language words around. One wonders if Gen.
> Alexander Haig was consulted on any of this, seeing as he was famous for
> turning nouns into verbs, etc.

A more concise statement of:

> turning nouns into verbs

is:

	verbing a noun

Re: package child question

[Pascal Obry]

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Larry Kilgallen a �crit dans le message <2000Feb10.072710.1@eisner>...
>In article <38A20732.F8119EBB@quadruscorp.com>, "Marin D. Condic"
<mcondic-nospam@quadruscorp.com> writes:
>
> verbing a noun

I like also : Every noun can be verbed.

Pascal.

--|------------------------------------------------------
--| Pascal Obry                           Team-Ada Member
--| 45, rue Gabriel Peri - 78114 Magny Les Hameaux FRANCE
--|------------------------------------------------------
--|         http://perso.wanadoo.fr/pascal.obry
--|
--| "The best way to travel is by means of imagination"

Re: package child question

[Steve Folly]

Jean-Pierre Rosen <rosen.adalog@wanadoo.fr> wrote in message
news:87rava$8dv$1@wanadoo.fr...
>
> >
> A funny and unfortunate effect of automatic lines folding!
> I wrote "start with Standard", I didn't suggest to have a "with
standard;".
> As an evidence of my innocence, notice that the word "Standard" is
followed
> by a colon, not a semi-colon :-)
>

Indeed, I bought some new eyes yesterday, and I can see fine now :-)
My apologies, Jean-Pierre.


--
Regards,
Steve Folly.
http://www.follysplace.demon.co.uk
donationsto:myaccount@mybank.co.uk