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.
>
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Received on Sat Feb 24 2007 - 23:10:56 UTC