Re: newbie problem

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

Olivier Scalbert wrote on comp.lang.ada:
> Problem 1: it does not compile !
> adasound.ads:23:10: completion of nonlimited type cannot be limited
> adasound.ads:23:10: component "File_Type" of type "Als_File_T" has
> limited type

File_Type is of a limited type; any type containing it must therefore
also be limited.  Martin and Adam explained that very well.  My
preferred solution would be to make Als_File_T limited, too, since it
also represents a file.

> Problem 2: how to avoid the first "with Sequential_Io;" ?

Solution 1, as explaines by Martin: private with Ada.Sequential_IO;
this assumes that the presence of the with clause is only a minor
problem.  I would tend to agree that this problem is minor.

Solution 2: If you absolutely want to hide the with clause, you can
move it to the body of your package by making Als_File_T completely
opaque, like so:

package Adasound is
   type Als_File_T is private; -- or limited private
private
   type Internal_T;
   type Als_File_T is access Internal_T;
end Adasound;

with Ada.Sequential_IO;
package body Adasound is
   package Stereo_Amplitude_IO is new Sequential_Io
(Stereo_Amplitude_T);
   type Internal_T is limited record
      File_Type : Stereo_Amplitude_IO.File_Type;
   end record;
end Adasound;

The drawback of making Als_File_T opaque is that not even child
packages of Adasound can see the internals of the type.  This may be a
problem if you want to write unit tests (which are often child
packages or child procedures of the unit under test).

--
Ludovic Brenta.