Re: Conditional Code in Ada 95?

[Richard D Riehle <laoXhai@ix.netcom.com>]

In article <6rtike$b3$1@nnrp1.dejanews.com>,
	dewarr@my-dejanews.com wrote:

>I can't see what has changed that should suggest reconsidering
>this decision. Steelman specified no conditional compilation in
>Ada, Ada 83 carefully considered that specification and agreed
>with it, and Ada 95 also agreed. I see no reason to revisit this
>unless there is new information, there has always been general
>agreement that conditional compilation does not belong in the
>language proper. Michael, what new information is available
>that would suggest revisiting it (the fact that Michael Brenner
>wants it does not count as new information :-)
>
There is probably nothing new information on this, Robert.  It does,
however, turn out to be a useful capability.  I have direct experience
with Ada development shops that have written their own conditional
compilation software.  One example is that of an Ada developer that
took advantage of the portability of vanilla-flavored Ada to do much
of its embedded software programming on a bunch of low-cost PC-based
computers.  They purchased one copy of the high-priced embedded
cross-compiler and used it only when necessary to target the actual
target processor.  Most of the other compilations were done using the
low-cost compilers.

The conditional compilation software eliminated comment lines for the
el-cheapo compiler so it could emulate the features of the target
computer.  When it came time to compile to the target, the conditional
compilation elminated comment lines for that compiler.   Of course,
hardware dependent code was, as much as possible, pushed to the 
lowest possible level of the design.  This turned out
to provide some cost savings for a large development team creating
Ada software for a non-military application.  As far as I know, they
are still using this technique.  It works for them and they are
very successful with Ada.

The downside of this usage of conditional compilation is that the
prices of embedded compilers stay high because fewer are sold.   

There are many other examples of conditional compilation in Ada that 
make sense.  I do agree with you Robert that it should not be a part
of the core language.  As an idea for some future Annex?  Maybe.

Richard
richard@adaworks.com
http://www.adaworks.com