Re: Subprogram Renaming

[dewar@cs.nyu.edu (Robert Dewar)]

Jonas asked:

"But it could be put in the private part, without 'exposing the renaming'.
Robert mentioned before that this had a performance drawback but I can't see
that this would be the case if you have a generic package."

No, the performance penalty of creating a body occurs only if the renaming
is in the body. Actually, as Bob Duff pointed out, not all compilers
will take advantage of the possible performance gain (equiavlent to
automatic inlining) that completion-with-renaming can provide (GNAT does
not, since it requires renaming capability at the linker level, a feature
that not all linkers provide). However, this performance penalty can in
any case be completely eliminated by use of pragma Inline so in the case
where the renaming-as-body appears in the body it is a shorthand and
nothing more.

In the private part it is a different feature, but I don't understand
Jonas' comment above. Sure in Ada 83 you could put a renaming in the
private part, and it wouldn't expose the renaming -- it also would not
expose ANYTHING and could not be used by a client of the package and
therefore would be completely useless!

The ability to use renaming-as-body in the private part is a new Ada 95
feature which is quite useful, sometimes it can completely eliminate a
package body that would otherwise be required in Ada 83.