Re: Standard Ada Preprocessor

["Randy Brukardt" <randy@rrsoftware.com>]

"Marin David Condic" <nobody@noplace.com> wrote in message
news:4011CF46.3040001@noplace.com...
...
> I've encountered all of these in real-world situations and sometimes I
> might have dealt with them by having separate bodies (often really
> difficult to manage in practice) or I dealt with them via conditional
> compilation because I was using C. I just know it happens enough where
> conditional compilation would be a useful thing and not always a matter
> of abuse. If someone thinks it isn't really needed because it can be
> dealt with via some kind of CM or build process - I'd suggest they need
> to work in some of the environments I've been in where you either don't
> have the tools or there are all sorts of complications that make this
> really hard to do.

You want to change the language because you've had to work in poorly managed
shops with insufficient tools? Sure, we all do what we have to do to get the
job done, but that hardly justifies a major language change (and one where
no obvious workable solution springs to mind).

> Conditional compilation isn't always pretty - but then neither are rep
> clauses or other things that are regularly done because that's the
> easiest way to get the job done.

I think you're comparing apples to oranges. Rep clauses are an elegant way
of getting the job done; the only alternative is bit mask operations and
those are a lot harder to understand. And they certainly aren't about just
interfacing to hardware - I use them a lot to reduce storage use without
making critical parts too slow. So I guess I'd say that rep. clauses ARE
pretty. You'd be better off picking on Access_to_Address_Conversions or
something like that -- except that no one much uses any of those packages.
Perhaps because they are ugly.

I'm not personally against conditional compilation, I just don't see any way
to integrate a useful form of it into the language. (I don't think it is
necessary in an ideal world, but the world is hardly ideal - people write
gibberish in C and Java after all.) The form that Janus/Ada has (and we no
longer use in new code because it isn't flexible enough) is a pure binary
in-or-out scheme intended solely for marking debugging code. ('@' is either
compiled as a comment "--" or as a space ' ' depending on the command line
options.) Pragmas have a number of problems: they can't be used in some
parts of the code (for example, formal_parts and discriminant_parts); such a
pragma would violate "good taste in pragmas" as laid out in 2.8; and enough
people think that they're ugly to prevent them from being used this way.
(GNAT's pragma Debug was considered and discarded for this reason.) Some
sort of syntax would be needed, and that seems like it would be pretty
heavy. (And I have no idea what it ought to look like.)

If you want to propose something, feel free, but remember that the ARG is
not taking new topics anymore, so unless you can find a way to coordinate it
with an existing AI, it will have to wait for Ada 1Z.

                      Randy.


All-in-all, it seems like there