[m-rev.] diff: mercury versions of library pragma foreign_procs

[Fergus Henderson]

On 12-Jun-2002, Ralph Becket <rafe at cs.mu.OZ.AU> wrote:
> Fergus Henderson, Tuesday, 11 June 2002:
> > 
> > There should be comments on all those calls to sorry/1, explaining that
> > this is just a default for back-ends that don't support the C interface.
> 
> But isn't that what sorry/1 says (well, omitting the specific reference
> to the C back end.)

Well, no; calling sorry/1 could mean that either
   (1) the feature is not implemented at all
or (2) this feature is implemented in foreign code, and
       the call to sorry/1 is just a default for back-ends
       that don't support any of the foreign languages in
       which the procedure has been implemented.

The message that sorry/1 prints out is

	"sorry, `" ++ PredName ++ "' not implemented\n" ++
                "for this target language (or compiler back-end)"

which, although emphasizing case (2), is intended to cover both cases.

Note that we also have sorry/2 in the compiler directory,
which is definitely for case (1).  The semantics of sorry/1 
in the library should be consistent with this.

Perhaps sorry/1 should be renamed default_sorry/1, and used only for case (2),
and we should add a new sorry/1 for case (1).

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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