Re: Visibility of package within package

[stt@henning.camb.inmet.com (Tucker Taft)]

Erik Masella (emasella@mtl.marconi.ca) wrote:

> Could anybody explain to me why the following will not work:
> 
> with Generic_Pkg;
> package A_Pkg is
>    package B_Pkg is new Generic_Pkg(...);
> ..
> end A_Pkg;
> 
> --------------------------------
> 
> with A_Pkg;
> package body C_Pkg is
>    procedure Init is
>    begin
>       A_Pkg.B_Pkg.Do_Something(...);
>    end Init;
> end C_Pkg;
> 
> ==> Why isn't B_Pkg visible within C_Pkg?  From what I understand,
> "Software Engineering with Ada" from Booch (2nd ed.) says at p.383 that
> this is possible (but he did not use generics).
> 
> I'd greatly appreciate some insight into this.

Tucker Taft wrote:

> Your code looks OK, but it is hard to be sure without a complete
> example, since we don't know what is inside "Generic_Pkg".  When
> you have mysteries like this, it is most useful to include an
> actual listing with error messages from the compiler.  Surprisingly
> often, there is some other problem than the one you first suspect.
> 
> In any case, it is possible that the compiler has a bug, but your
> example is so simple and straightforward that it seems more likely
> that something else is wrong.

Chad Bremmon (chad.bremmon@comm.hq.af.mil) wrote:

> Don't you still have to with in "With A_Pkg.BPkg;" inside of your C_Pkg ?

No.  B_Pkg is not a separate library unit.  You only need to mention
library units in "with" clauses.  B_Pkg is physically nested inside
A_Pkg, so it is a mystery why the above doesn't compile.  Again, a
complete example, with compiler messages, is the only way to figure it out.

> Chad

: > : Erik Masella
: > : emasella@mtl.marconi.ca

-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Cambridge, MA  USA