Re: ada -> C translator

[William Clodius <wclodius@lanl.gov>]

Richard A. O'Keefe wrote:
> <snip>
> Nor has Fergus said that "portable C is portable C and that is that".
> His claim, as I understood it, was that one can translate a source
> program that is intended to be portable to C that can adapt to particular
> targets but is usable on many.  Talking about interfacing to COBOL misses
> _his_ point, because in that case the source program isn't _intended_ to
> be portable (the porting target might not _have_ a COBOL compiler).
> <snip>

Both Robert Dewar and Fergus Henderson are talking past one another.
Robert argues that there are significant machine dependencies in the
translation of Ada, Fergus argues that any given machine dependency can
be handled using conditional compilation. Both statements are valid and
not in contradiction, but both are misleading.

Fergus's points are perfectly valid for Mercury, however, this thread is
not about compiling Mercury to C, but about compiling Ada to C. As a
logic programming language Mercury is much more distant from the machine
than is Ada. An Ada compiler to retain efficiency and correctness of
translation has to be more sensitive than Mercury to machine (and C
compiler) differences.  If the amount of code that is processor
independent is relatively small, then the usefullness of C as a portable
language vanishes. The problem is not that conditional compilation
cannot in principle be used to address these issues, which is what
Robert Dewar's arguments seem to suggest, but rather that in the case of
Ada what is possible in principle is impractical in practice.

-- 

William B. Clodius		Phone: (505)-665-9370
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