[Openmcl-devel] two portability issues

Rainer Joswig joswig at lisp.de
Sun Dec 21 01:34:21 UTC 2014


>>> 
>>> ** second issue:  LOOP clause MAXIMIZE**
>>> in above function there is a clause  MAXIMIZE … FIXNUM .
>>> In CCL (and several other implementations, with the exception of LispWorks) this causes that a wrong result (a negative number) is computed. Without the FIXNUM declaration the result is correct.
>> 
>> Does it return the same result (perhaps more slowly) if the FIXNUM declaration is retained and the OPTIMIZE declaration is changed to something like (SAFETY 3) (SPEED 0) ?
> 
> The problem seems to appear without optimize declarations...
> 
> (defun get-longest-path (nodes node-id visited &aux (max 0))
>   (setf (svref visited node-id) t)
>   (setf max (loop for neighbour of-type route in (svref nodes node-id)
>                   unless (svref visited (route-dest neighbour))
>                   maximize (+ (the fixnum (route-cost neighbour))
>                               (the fixnum (get-longest-path nodes
>                                                             (route-dest neighbour)
>                                                             visited)))
>                             fixnum))
>   (setf (svref visited node-id) nil)
>   max)
> 
> Safety 3 and Speed 0 takes a long time and returns the wrong result: -1152921504606837995
> 
> The expected result would have been 8981.

it works for real, but not fixnum… The computed numbers are not outside the fixnum range, though.

   … maximize (…) real )  works



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.clozure.com/pipermail/openmcl-devel/attachments/20141221/1d4b90c7/attachment.html>


More information about the Openmcl-devel mailing list