On Jul 25, 2012, at 5:51 PM, Jens Axel Søgaard wrote: > 2012/7/25 Matthias Felleisen <[email protected]>: >> >> Yes, the #:when clause has to be last. I got my reasoning backwards. >> >> Do try both and report back. I am curious how expensive the ec is compared >> to the #:when test. > > It turned out that the for*/fold + #:when solution didn't behave as expected. > Here is the documentation of for/vector : > > -- > > (for/vector (for-clause ...) body ...+) > (for/vector #:length length-expr (for-clause ...) body ...+) > > Iterates like for/list, but the result are accumulated into a vector > instead of a list. If the optional #:length form is used, then > length-expr must evaluate to an exact-nonnegative-integer?, and the > result vector is constructed with this length. In this case, the > iteration can be performed more efficiently, and terminates when the > vector is full or the requested number of iterations have been > performed, whichever comes first. > > -- > > I interpret this paragraph to mean, that > > (for/vector #:length 10 ([i (in-naturals)]) i) > > ought to terminate - but it doesn't ! > > The question is now, whether the bug is in the documentation, the > implementation > or my interpretation.
There is certainly a conflict between the docs and the behavior. I think the docs describe the desirable behavior so I suggest you submit a bug report against the code. If this is wrong, I am sure Matthew will let us know. ____________________ Racket Users list: http://lists.racket-lang.org/users
