I would expect (k) to be the same. Otherwise fluids would not mix well with undo redo sematics. But I do understand that people might have decided that it should work like this. and knowing the this semantic, one can fix the problem. If the semantics is correct I really can't find an example where it is useful though. Do you have an example?
/Stefan On Sat, Mar 23, 2013 at 3:51 PM, Daniel Hartwig <mand...@gmail.com> wrote: > On 23 March 2013 18:41, Stefan Israelsson Tampe <stefan.ita...@gmail.com> > wrote: >> Consider this simple exmple with fluids and reodos via propmts, >> >> (define (f x) >> (let ((s (make-fluid 0))) >> (with-fluids ((s 0)) >> (let lp ((i 0)) >> (cond ((>= i 100) (fluid-ref s)) >> ((= i 50) (abort-to-prompt 'tag) (lp (+ i 1))) >> (else (fluid-set! s (+ (fluid-ref s) i)) >> (lp (+ i 1)))))))) >> >> (define k (call-with-prompt 'tag (lambda () (f 1)) (lambda (k . l) >> k))) >> >> Then we will get in guile-2.0 pretty resent git version >> scheme@(guile-user)> (k) >> $1 = 4900 >> scheme@(guile-user)> (k) >> $2 = 8575 >> > > What values do you expect from successive calls to K? > >> The reason is that when the with-fluid returns normally it does a full >> swap. It should only do half a swap e.g. restore the old value of the >> fluid and not store the current which is of non use because it can not >> be reached anymore and it contaminates the continuation k. > > K captures S, a fluid, along with the dynamic extent. There is only a > single dynamic extent to which K resumes, and only one value > associated to the fluid S within that. Subsequent calls to K do not > generate a new dynamic extent, so it makes sense that modifications to > the fluids value persist. This example behaives as expected according > to my understanding of fluids. > > Am I missing something?
