Procedure defined in package body accessed by separate procedure

Procedure defined in package body accessed by separate procedure

[ashwath30jul77]

Hello,
I am getting an error when a procedure(say Pr1) defined in a separate file invokes a procedure defined in the package(say Pk1) body(say Pr2). The compiler gives error saying that Pr2 is not declared in Pk1. 

Please let me know what is the mistake I am doing.

Snapshots of source code is shown for better clarity.

Greetings.ads:
=============================
package Greetings is

   procedure Hello;
   procedure Goodbye;

end Greetings;

Greetings.adb:
==============================
with text_io;
use Text_IO;

package body Greetings is

   procedure Hello is separate;
   procedure Goodbye is separate;
   procedure proc_body is
   begin
      put_line("body");
   end;
end Greetings;

Greetings-Hello.ada:
================================
with text_io;
use Text_IO;
separate (Greetings)

procedure Hello is
begin
   put_line("Hello");
   Greetings.proc_body;--Compiler error here. Says proc_body is not declared in Greetings
end;

I am using GNAT pro to compile this.

Thanks in Advance
Ashwath

Re: Procedure defined in package body accessed by separate procedure

[G.B.]

On 13.02.14 13:15, ashwath30jul77@gmail.com wrote:

> package body Greetings is
>
>     procedure Hello is separate;
>     procedure Goodbye is separate;
>     procedure proc_body is
>     begin
>        put_line("body");
>     end;
> end Greetings;
>
> Greetings-Hello.ada:
> ================================
> with text_io;
> use Text_IO;
> separate (Greetings)
>
> procedure Hello is
> begin
>     put_line("Hello");
>     Greetings.proc_body;--Compiler error here. Says proc_body is not declared in Greetings
> end;

Linearity of reading seems at work here: proc_body, in body
Greetings, appears after the line that says "Hello is
separate". Therefore, when that line is "evaluated", there
is no procedure proc_body (yet).
To resolve the issue, either put a specification of
procedure proc_body before "... Hello is separate", or put
the latter line after proc_body's definition.

Re: Procedure defined in package body accessed by separate procedure

[adambeneschan]

On Thursday, February 13, 2014 5:58:33 AM UTC-8, G.B. wrote:
 
> > package body Greetings is 
> >     procedure Hello is separate; 
> >     procedure Goodbye is separate; 
> >     procedure proc_body is
> >     begin
> >        put_line("body");
> >     end;
> > end Greetings;

> > Greetings-Hello.ada:
> > ================================
> > with text_io;
> > use Text_IO;
> > separate (Greetings)
> > procedure Hello is
> > begin
> >     put_line("Hello");
> >     Greetings.proc_body;--Compiler error here. Says proc_body is not declared in Greetings
> > end;
> 
> Linearity of reading seems at work here: proc_body, in body
> Greetings, appears after the line that says "Hello is
> separate". Therefore, when that line is "evaluated", there
> is no procedure proc_body (yet).

Yes, that's the reason.  The RM says (10.1.3(17)):

"Visibility within a subunit is the visibility that would be obtained at the place of the corresponding body_stub (within the parent body) if the context_clause of the subunit were appended to that of the parent body."

So that means that the things that are visible to Hello's separate body are the same things that would be visible at the place the "procedure Hello is separate" (the body stub) appeared.  If there were a *new* "with" or "use" clause on the separate body, that would make other things visible as well.  In this case, since there is already "with Text_IO; use Text_IO;" on the body of Greetings, the WITH and USE on the body of Hello doesn't make anything else visible.  (In fact, they're redundant and could be removed.  My personal preference is to include redundant WITH's and USE's anyway, so that you don't have to flip between a bunch of source files to figure out what WITH's and USE's are in effect.)  But anyway, if you wrote all of Hello inline in the body of Greetings, instead of making it separate, you'd get the same error on proc_body; therefore, the same error occurs in the separate body, since the same identifiers are visible.

                                -- Adam

Re: Procedure defined in package body accessed by separate procedure

[ashwath30jul77]

On Thursday, February 13, 2014 10:24:53 PM UTC+5:30, adambe...@gmail.com wrote:
> On Thursday, February 13, 2014 5:58:33 AM UTC-8, G.B. wrote:
> 
>  
> 
> > > package body Greetings is 
> 
> > >     procedure Hello is separate; 
> 
> > >     procedure Goodbye is separate; 
> 
> > >     procedure proc_body is
> 
> > >     begin
> 
> > >        put_line("body");
> 
> > >     end;
> 
> > > end Greetings;
> 
> 
> 
> > > Greetings-Hello.ada:
> 
> > > ================================
> 
> > > with text_io;
> 
> > > use Text_IO;
> 
> > > separate (Greetings)
> 
> > > procedure Hello is
> 
> > > begin
> 
> > >     put_line("Hello");
> 
> > >     Greetings.proc_body;--Compiler error here. Says proc_body is not declared in Greetings
> 
> > > end;
> 
> > 
> 
> > Linearity of reading seems at work here: proc_body, in body
> 
> > Greetings, appears after the line that says "Hello is
> 
> > separate". Therefore, when that line is "evaluated", there
> 
> > is no procedure proc_body (yet).
> 
> 
> 
> Yes, that's the reason.  The RM says (10.1.3(17)):
> 
> 
> 
> "Visibility within a subunit is the visibility that would be obtained at the place of the corresponding body_stub (within the parent body) if the context_clause of the subunit were appended to that of the parent body."
> 
> 
> 
> So that means that the things that are visible to Hello's separate body are the same things that would be visible at the place the "procedure Hello is separate" (the body stub) appeared.  If there were a *new* "with" or "use" clause on the separate body, that would make other things visible as well.  In this case, since there is already "with Text_IO; use Text_IO;" on the body of Greetings, the WITH and USE on the body of Hello doesn't make anything else visible.  (In fact, they're redundant and could be removed.  My personal preference is to include redundant WITH's and USE's anyway, so that you don't have to flip between a bunch of source files to figure out what WITH's and USE's are in effect.)  But anyway, if you wrote all of Hello inline in the body of Greetings, instead of making it separate, you'd get the same error on proc_body; therefore, the same error occurs in the separate body, since the same identifiers are visible.
> 
> 
> 
>                                 -- Adam

Thanks for response Adam.
Is this compiler specific?It seems to compile when Tartan compiler is used :S

Re: Procedure defined in package body accessed by separate procedure

[Simon Wright]

ashwath30jul77@gmail.com writes:

> Is this compiler specific?It seems to compile when Tartan compiler is
> used :S

That would be a bug in the Tartan compiler.

And, could you _please_ trim irrelevant lines? Google Groups may hide
them, but other newsreaders don't.

Re: Procedure defined in package body accessed by separate procedure

[Dirk Heinrichs]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

ashwath30jul77@gmail.com wrote:

> Hello,
> I am getting an error when a procedure(say Pr1) defined in a separate file
> invokes a procedure defined in the package(say Pk1) body(say Pr2). The
> compiler gives error saying that Pr2 is not declared in Pk1.
> 
> Please let me know what is the mistake I am doing.
> 
> Snapshots of source code is shown for better clarity.
> 
> Greetings.ads:
> =============================
> package Greetings is
> 
>    procedure Hello;
>    procedure Goodbye;
> 
> end Greetings;
> 
> Greetings.adb:
> ==============================
> with text_io;
> use Text_IO;
> 
> package body Greetings is
> 
>    procedure Hello is separate;
>    procedure Goodbye is separate;
>    procedure proc_body is
>    begin
>       put_line("body");
>    end;
> end Greetings;
> 
> Greetings-Hello.ada:
> ================================
> with text_io;
> use Text_IO;
> separate (Greetings)

Should be "with Greetings;"
 
> 
> procedure Hello is
> begin
>    put_line("Hello");
>    Greetings.proc_body;--Compiler error here. Says proc_body is not
>    declared in Greetings

Which is correct, because it's not in the spec. As long as it's in the body 
only, you can't call it from other packages.

HTH...

	Dirk
- -- 
Dirk Heinrichs <dirk.heinrichs@altum.de>
Tel: +49 (0)2471 209385 | Mobil: +49 (0)176 34473913
GPG Public Key CB614542 | Jabber: dirk.heinrichs@altum.de
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Re: Procedure defined in package body accessed by separate procedure

[adambeneschan]

On Thursday, February 13, 2014 8:32:53 AM UTC-8, Dirk Heinrichs wrote:

> 
> > with text_io;
> > use Text_IO;
> > separate (Greetings)
> 
> Should be "with Greetings;"

No, this is misinformation.  separate(Greetings) is correct.

                       -- Adam

Re: Procedure defined in package body accessed by separate procedure

[Dirk Heinrichs]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

adambeneschan@gmail.com wrote:

>> > separate (Greetings)
>>
>> Should be "with Greetings;"
> 
> No, this is misinformation.  separate(Greetings) is correct.

Hmm, I thought I could only use that in sub units.

Bye...

	Dirk
- -- 
Dirk Heinrichs <dirk.heinrichs@altum.de>
Tel: +49 (0)2471 209385 | Mobil: +49 (0)176 34473913
GPG Public Key CB614542 | Jabber: dirk.heinrichs@altum.de
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Re: Procedure defined in package body accessed by separate procedure

[Dirk Heinrichs]

Dirk Heinrichs wrote:

>>> > separate (Greetings)
>>>
>>> Should be "with Greetings;"
>>
>> No, this is misinformation.  separate(Greetings) is correct.
> 
> Hmm, I thought I could only use that in sub units.

Ah, sorry. Didn't see that the last file actually IS a sub unit (Greetings-
Hello.ada).

Bye...

	Dirk
-- 
Dirk Heinrichs <dirk.heinrichs@altum.de>
Tel: +49 (0)2471 209385 | Mobil: +49 (0)176 34473913
GPG Public Key CB614542 | Jabber: dirk.heinrichs@altum.de