Obviously Will was not suggesting that compilers reject
programs that cannot be proven to terminate.
On 2/24/07, Thomas Lord <lord_at_emf.net> wrote:
> I think the standard has failed to be a lisp, and failed in the
> Scheme tradition, if it does not permit viable non-standard
> interpretations of programs which are divergent under the
> standard (see my earlier post "Mathematical Foundations").
>
> For example, suppose that a procedure which is not provably
> terminating in a portable interpretation has the property that,
> nevertheless, we can say that *if* it terminates, the type of
> the return value is CHAR?. Further, suppose the procedure
> is invoked in a context that is only strict in the type of the
> return value.
>
> Must R6RS prohibit an implementation from completing this
> computation?
>
> Before answering, please read "On Games and Numbers".
>
> Regards,
> -t
>
>
>
> Arthur A. Gleckler wrote:
> > On Feb 24, 2007, at 4:54 PM, William D Clinger wrote:
> >
> >> Matthias Felleisen wrote:
> >>> 2. Naturally I don't reject type systems per se but I think that a
> >>> serious
> >>> language definition shouldn't introduce such systems without
> >>> specifying
> >>> them. Otherwise a language/implementation will appear whimsical to
> >>> programmers.
> >>
> >> The current draft already mandates hundreds of runtime
> >> exceptions whose whimsical purpose is to make programs
> >> that violate the requirements of the R6RS less likely
> >> to run to completion. Why should that kind of whimsy
> >> be limited to run time?
> >
> > My only concern is that an error in one part of my program should not
> > prevent me from running another part of the program. The thing I most
> > dislike about most statically typed language implementations is that
> > they prevent me from testing a program that isn't yet completely
> > type-correct when I'm not even planning to invoke the broken part of
> > the program. I suppose that this suggestion only allows, but doesn't
> > require, compiler writers to signal errors it can detect at compile
> > time. Still, I'd rather not encourage this behavior if it makes it
> > impossible to run programs that are not yet completely correct.
> >
> > _______________________________________________
> > r6rs-discuss mailing list
> > r6rs-discuss_at_lists.r6rs.org
> > http://lists.r6rs.org/cgi-bin/mailman/listinfo/r6rs-discuss
> >
>
>
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>
--
~jrm
Received on Sun Feb 25 2007 - 00:07:34 UTC