[racket] Behavior of continuation-mark-set->list and continuation-mark-set-first with respect to key values

Do you mean to just leave the quote off of the usage example?

If not, you could do something like the below (note that this doesn't
do a good job of error reporting and the test module requires a git
version of racket to run).

Robby

#lang racket

(define-syntax-rule
  (with-continuation-marks keys vals body)
  (with-continuation-marks/proc keys vals (λ () body)))

(define (with-continuation-marks/proc keys vals thunk)
  (let loop ([keys keys]
             [vals vals])
  (cond
    [(null? keys)
     (thunk)]
    [else
     (with-continuation-mark (car keys) (car vals)
       (loop (cdr keys)
             (cdr vals)))])))

(module+ test
  (require rackunit)
  (check-equal?
   (continuation-mark-set->list
    (with-continuation-marks '(id1 id2 id3)
                             '(1 2 3)
                             (current-continuation-marks))
    'id1)
   '(1)))


On Sun, May 6, 2012 at 8:10 PM, Galler <lzgaller at optonline.net> wrote:
> Thanks Robby.
>
> I'm attempting to implement the behavior described in Section 3.2 of your
> 2007 paper, specifically
>
> "each continuation frame can have any number of marks with distinct keys"
>
> by defining a new 'with-continuation-marks' syntax which will set up
> arbitrary number of nested 'with-continuation-mark' calls in response to a
> list of keys
>
> As Eli B. picked up on earlier, I'm having trouble with Chapter 16 of the
> Racket Guide and its a mess at the moment.
>
>
>
> Is there a basic example of pattern matching for a list of arbitrary number
> of elements (including zero)? I
>
>
> ; usage (with-continuation-marks '(id1 id2 id3) body)
>
> ;this doesn't work because of bad pattern matching in the
> with-continuation-marks macro.  (make-binding ...) just sets up storage.
> ;its the '(id1 id2 id3) in the arguments that's causing the problem.
>
>
> (define-syntax with-continuation-marks
>  (syntax-rules ()
>    [(with-continuation-marks (id) body) (with-continuation-mark id
> (make-binding id) body)]
>    [(with-continuation-marks (id1 id2 ...) body) (with-continuation-mark id1
> (make-binding id1) (with-continuation-marks (id2 ...) body ))]))
>
>
>
> On Sun, May 6, 2012 at 9:56 AM, Robby Findler wrote:
>
>> continuation-mark-set->list always does return all of the bindings,
>> but continuation marks are carefully designed to avoid breaking tail
>> recursion (they let you understand the tail behavior of your program,
>> more accurately) so that's why you see only one binding.
>>
>> continuation-mark-set-first can be more efficient than
>> continuation-mark-set->list and it is more likely to work in futures.
>> That's the only reason it exists.
>>
>> Robby
>>
>> On Sat, May 5, 2012 at 11:02 PM, Galler <lzgaller at optonline.net> wrote:
>>>
>>> BACKGROUND:
>>>
>>> Per the documentation:
>>>
>>> with-continuation-mark  causes a key to be associated with a binding
>>> within
>>> a continuation frame
>>>
>>> continuation-mark-set->list returns the binding(s) associated with that
>>> particular key, for any given continuation-mark-set
>>>
>>> while
>>>
>>> continuation-mark-set-first returns the first (innermost) binding
>>> associated
>>> with a particular key
>>>
>>> QUESTIONABLE  BEHAVIOR
>>>
>>> The issue is:
>>>
>>> if a key is reused, the only binding continuation-mark-set->list returns
>>> is
>>> the innermost binding.
>>>
>>> So continuation-mark-set->list could only possibly return **one** value
>>>
>>> and
>>>
>>> continuation-mark-set-first  appears redundant
>>>
>>> Is that the desired behavior? I would have expected
>>> continuation-mark-set->list to return all the bindings for a particular
>>> key.
>>>
>>> Additionally, I suspect continuation-mark-set->context has to be
>>> implemented
>>> using the 'return a list of all bindings for a single key' behavior,
>>> since
>>> the documentation indicates it uses a single private key.
>>>
>>>
>>> EXAMPLE
>>>
>>> #lang racket
>>> (with-continuation-mark 'global  'outermost-value
>>>  (let/cc k-outer
>>>    (with-continuation-mark 'global 'middle-value
>>>      (let/cc k-inner
>>>        (with-continuation-mark 'global 'inner-value (begin
>>>                                                       (display
>>> (continuation-mark-set->list (current-continuation-marks) 'global))
>>>                                                       (newline)
>>>                                                       (display
>>> (continuation-mark-set->list (continuation-marks k-inner) 'global))
>>>                                                       (newline)
>>>                                                       (display
>>> (continuation-mark-set->list (continuation-marks k-outer) 'global))
>>>         ))))))
>>>
>>> ;Returns
>>>
>>> ;(inner-value)
>>>
>>> ;(middle-value)
>>>
>>> ;(outermost-value)
>>>
>>> but I would have expected:
>>>
>>> ;Returns
>>>
>>> ;(inner-value) (middle-value) (outermost-value)
>>>
>>> ;(middle-value) (outermost-value)
>>>
>>> ;(outermost-value)
>>>
>>>
>>> Thanks very much for looking at this.
>>>
>>> R/
>>>
>>> Zack
>>> ____________________
>>>  Racket Users list:
>>>  http://lists.racket-lang.org/users