Re: Package's private parts and protected types

[Adam Beneschan <adam@irvine.com>]

On Feb 9, 6:56 am, Robert A Duff <bobd...@shell01.TheWorld.com> wrote:
> AdaMagica <christoph.gr...@eurocopter.com> writes:
> > OK, but then you have a similar problem to Ada83's syntactically
> > unneeded bodies which Ada95 solved with a pragma.
>
> I think that problem is an illusion.  There was a problem,
> but it was a problem with implementations, not with the
> language.  How do we know if a given package spec has
> a body?  Simple: look on the disk and see if there's
> a source file containing that body.  In GNAT, that would
> mean looking for foo.adb.

And for other implementations (that put fewer restrictions on the
names and locations of source files containing the Ada source), that
would mean searching every file on the disk to see if one of them had
"package body foo" in it.  :) :)

I know---those other implementations wouldn't do things this way;
they'd provide some other mechanism to allow a programmer to tell the
compilation system that a package no longer requires a body---or does
require a body.  But you should be careful when you say things like
"Simple...".  Unless, of course, you were joking.  Anyway, the problem
was certainly solvable in any implementation, although as Randy points
out it's still not ideal because it makes it too easy for an
accidental error to result in the compiler accepting a package without
a body that's supposed to have one, or vice versa, causing incorrect
results at runtime that could be puzzling to track down.  And that
issue exists with GNAT also---you delete some files from your
directory with a wildcard, somehow foo.adb accidentally gets deleted
along with them, and the compiler still thinks your program is OK.

                                      -- Adam