[plt-scheme] Please help test version 359.100

The function for-each used to always return void. Now, it returns the  
result of calling its functional argument on the last element of the  
list.

In code, it used to do this:

(define (for-each f l)
   (cond
     [(null? l) (void)]
     [else (begin (f (car l)) (for-each f (cdr l)))]))

Now it behaves like this:

(define (for-each f l)
   (cond
     [(null? l) (void)]
     [(null? (cdr l)) (f (car l))]
     [else (begin (f (car l)) (for-each f (cdr l)))]))

I believe this change is going to be a part of r6.

Robby

On Nov 6, 2006, at 9:59 AM, Williams, M. Douglas wrote:

> I have a problem that seems to have cropped up somewhere between 352.4
> and 352.8 and is still in 359.100.  If you download the inference
> collection from PLaneT as follows:
>
> (require (planet "inference.ss" ("williams" "inference.ss)))
>
> Find and run ancestor.ss (the simplest example) from the examples
> directory - from the downloaded PLaneT package.
>
> Under 352 (and up to at least 352.4), it runs fine.  Under later
> versions - I noticed it first under 352.8 and it's still in 359.100 -
> you get the following error:
>
> context expected 1 value, received 0 values
>
> Or, if I run a local copy instead of the PLaneT copy [so I can change
> the code] and use (require "../inference.ss")
>
> ..\private\inference-control.ss::25016: context expected 1 value,
> received 0 values
>
> This points to the following code as the problem:
>
>   (define (match-node-retract match-node assertion)
>     (set-match-node-n! match-node (- (match-node-n match-node) 1))
>     (let/cc exit
>       (let loop ((previous #f)
>                  (matches (node-matches match-node)))
>         (when (not (null? matches))
>           (let ((match (car matches)))
>             (when (eq? assertion (caar match))
>               ;; Remove the match
>               (if previous
>                   (set-cdr! previous (cdr matches))
>                   (set-node-matches! match-node (cdr matches)))
>               (for-each
>                (lambda (successor)
>                  (unpropagate-match-from-match-node match successor))
>                (node-successors match-node))
>               (exit)))
>           (loop matches (cdr matches))))
>       ;; Match not found
>       (for-each
>        (lambda (successor)
>          (unpropagate-nonmatch-from-match-node successor))
>        (node-successors match-node))))
>
> The problem is the (exit) with no value.  None of the upstream code  
> uses
> the return value from match-node-retract.  The only usage (and the one
> that fails) is in the following - within the for-each:
>
>   (define (retract assertion)
>     (when (current-inference-trace)
>       (printf "<<< ~a~n" assertion))
>     ;; Remove the fact from the assertion index.
>     (hash-table-put! (current-inference-assertion-index)
>                      (fact-first (assertion-fact assertion))
>                      (delete! assertion
>                               (hash-table-get
>                                (current-inference-assertion-index)
>                                (fact-first (assertion-fact
> assertion)))))
>     ;; Match and unpropagate through the rule network.
>     (for-each
>      (lambda (match-node)
>        (match-node-retract match-node assertion))
>      (hash-table-get (current-inference-data-index)
>                      (fact-first (assertion-fact assertion)))))
>
> If I change the (exit) to (exit #f), the code doesn't fail, but it  
> gives
> an incorrect result - it seems to terminate at that point.
>
> If I change the (exit) to (exit '()) [or, it seems, to anything other
> than #f (including (exit (void)))], it works correctly.
>
> Does anyone have any idea what the problem is?
>
> Doug
>
>> -----Original Message-----
>> From: plt-scheme-bounces at list.cs.brown.edu [mailto:plt-scheme-
>> bounces at list.cs.brown.edu] On Behalf Of Eli Barzilay
>> Sent: Saturday, November 04, 2006 9:22 AM
>> To: plt-scheme at list.cs.brown.edu
>> Subject: [plt-scheme] Please help test version 359.100
>>
>> Version 359.100 is now available for testing from
>>
>>   http://pre.plt-scheme.org/installers/
>>
>> (Note that this not available from the usual download site.)
>>
>> If all goes well, we will turn this version into a v360 release  
>> within
>> a couple of weeks.
>>
>> This is, again, a release that is more substantial than the normal
>> releases -- there are many new features that are now part of PLT,
>> including the #px syntax for sophisticated "regular" expressions,
>> delimited continuations and a library of control operators, the
>> readline interface, the macro debugger, Lazy Scheme, and a host of
>> additional optimizations and fixes -- including improved support for
>> international keyboards.
>>
>> Your help in testing this new release candidate would be much
>> appreciated.
>>
>> --
>>           ((lambda (x) (x x)) (lambda (x) (x x)))          Eli
> Barzilay:
>>                   http://www.barzilay.org/                 Maze is
> Life!
>> _________________________________________________
>>   For list-related administrative tasks:
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