Re: Standard Ada Preprocessor

[Ole-Hjalmar Kristensen <ole-hjalmar.kristensen@substitute_employer_here.com>]

>>>>> "JC" == Jeffrey Carter <spam@spam.com> writes:

    JC> Warren W. Gay VE3WWG wrote:
    >> Jeffrey Carter wrote:
    >> 

    >>> One standard POSIX-Ada binding

    >> Impossible. Some UNIces provide some API structure members,

    >> while others don't, or provide something else again. Yes,
    >> you can dumb it down to a "standard" (or omit non-universal
    >> functionality), but by doing so you throw away functionality.
    >> I find that unacceptable.

    JC> There is a standard POSIX-Ada binding (Florist is an implementation of
    JC> this standard)  to the  POSIX standard. If  you want something  not in
    JC> this standard, obviously  you're going to have to  provide it yourself
    JC> on some platforms.  If you're on a platform  that doesn't provide some
    JC> of the  functionality, then it's not  a POSIX system.  In neither case
    JC> are you dealing with different versions of POSIX.

Which does not matter if what you are doing is maintaining a program
which is running on multiple platforms and is compiled with multiple
compilers. The program has to run even if the platform does not
support a standard package like Florist. How many platforms is Florist
really available on, btw.? 

What matters is how do I do this while keeping the code readable and
maintainable.

One way to combat the combinatorial explosion of platforms * compiler
* library is to explicitly test for the features of the environment
you really need to know, not assume something because of a particular
platform/compiler. This is the approach typically used by projects
using the 'configure' tool.

I would really like to have some standard configuration tool which
could take such parameters as input and produce a version of the
system tailored to the environment in which it is to be compiled and
run. 

In absence of this, I have to do the job manually, or use some kind of
preprocessing. Btw., such a configuration tool would have to keep the
exact same information internally as the condtional compilation rules
handled by the preprocessor. The only difference is that with the
preprocessor, the programmer can see the rules as part of the program
text. 


    JC> -- 
    JC> Jeff Carter
    JC> "Beyond 100,000 lines of code you
    JC> should probably be coding in Ada."
    JC> P. J. Plauger
    JC> 26


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   C++: The power, elegance and simplicity of a hand grenade.