Re: AQ&S Guidance on pragma Elaborate_Body

[bobduff@world.std.com (Robert A Duff)]

In article <mheaney-ya023680002404970907100001@news.ni.net>,
Matthew Heaney <mheaney@ni.net> wrote:
>It may be true that it "is not that uncommon," but mutual dependency of
>packages indicates that you have a pair of highly cohesive abstractions,
>and they should really be combined into a single package.

I strongly disagree.  Yes, they're highly cohesive (which is why one can
tolerate Elab instead of Elab_All in these cases), but that doesn't mean
you should always combine them.  Consider a compiler (I always use
compilers as examples, since that's what I do for a living): you might
want to define a bunch of types representing pieces of syntax trees, and
operations on those trees.  Lots and lots of things will refer to
"Expression_Ptr", and there are lots of kinds of expressions, and so
forth, so your suggestion would require lumping just about everything
into one package.  This is because everything in the language definition
is highly mutually recursive (statements contain expressions,
expressions contain statements (in some languages), statements contain
declarations, declarations contain statements, etc).

I wish Ada 95 had *better* support for mutually recursive abstractions
(remember that long thread of a year or two ago?) -- I certainly don't
think mutually recursive packages are inherently evil.

- Bob