Re: Future Ada language revisions?

[dewarr@my-dejanews.com]

In article <Pine.BSF.4.02A.9810050914220.9326-100000@shell5.ba.best.com>,
  Brian Rogoff <bpr@shell5.ba.best.com> wrote:
> Actually Alfred, Ada 95 *does* support the equivalent of C function
> pointers, although you'll have to use the Ada terminology "access to
> subprogram" to find them.
>
> If you really want to be a trouble-maker, you'll complain that the
> limitations on them make them only as powerful as C's function pointers,
> and less powerful than Pascal's function arguments (terminology?), and in
> that case I can point you directly to the long arguments on why they are
> so restricted :-)


Well Brian has a (well known to us here) axe to grind here, but the above is
a bit misleading. In fact in most respects the access-to-procedure values of
Ada are far more powerful than the procedure parameters of Pascal, in that
they are non-limited types that can be freely assigned. Yes it is true that
there are some limitations on the use of procedure parameters referring to
nested procedures, but on the other hand, many of the purposes for which
procedure parameters are used in Pascal are preferably implemented using
generics in the case of Ada, which are far more powerful than anything
Pascal has to offer.

For a good idea of how the use of generics and access-to-procedure approaches
compare, look at the g-hesorg.ads/adb and g-hesora.ads/adb files in the GNAT
distribution, these are respectively a generic and access-to-procedure
implementation of an optimized heapsort that does N log N comparisons (instead
of the usual 2 N log N).

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