[Openmcl-devel] need some help with "Unhandled exception"

[Taoufik Dachraoui]

Hi

Thank you for the rapid reply

the select accepts a pattern with special variables (?x, ?y, ...)

The select when it founds a bound special variable ?x it will replace it by
its value in the pattern

Example: with ?x unbound (select-loop (p ?x a) collect it) will return all
expressions in the db where the first and the third
elements are p and a respectively, but if ?x is bound to Z say, then the
select will return (p Z a) if it exists in the db

I did this in order to embed queries like the following:

(select-loop (p ?x a) append (select-loop (?x ?y) collect it)  (the second
?x will be bound to the value of ?x returned by the
first select (nested loops)

I did not see the infinite loop I will check again and see if I can solve
this

Thanks
Taoufik



On Sat, Dec 28, 2013 at 10:06 PM, Ron Garret <ron at flownet.com> wrote:

> You have an infinite loop in your macroexpansion:
>
> ? (macroexpand-all '(ancestor ?x a))
> > Error: Stack overflow on value stack.
>
> Also, I have no idea what this code is intended to do, but whatever it is
> this almost certainly isn’t helping:
>
> ? (pprint (macroexpand '(ancestor ?x a)))
>
> (LET ((?X '?X) (?Y 'A))
>   (DECLARE (SPECIAL ?X ?Y))
>   (IF (VAR? ?X) (MAKUNBOUND ?X))
>   (IF (VAR? ?Y) (MAKUNBOUND ?Y))
>   (UNION (SELECT-LOOP (P ?X ?Y) COLLECT IT)
>          (SELECT-LOOP (P ?X ?Z) APPEND (ANCESTOR ?Z ?Y))))
>
> You are binding ?X to itself, and then immediately making it unbound
> again.  That is almost certainly not what you want to do.
>
> rg
>
>
> On Dec 28, 2013, at 12:05 PM, Taoufik Dachraoui <
> dachraoui.taoufik at gmail.com> wrote:
>
> > Hi
> >
> > Could you please check this "Unhandled exception" and explain what is
> wrong
> > with my code
> >
> > (defun var? (x)
> >   (and (symbolp x) (not (keywordp x)) (eq (char (symbol-name x) 0) #\?)))
> >
> > (defun vars-in (expr)
> >   (if (atom expr)
> >       (if (var? expr) (list expr))
> >       (union
> >        (vars-in (car expr))
> >        (vars-in (cdr expr)))))
> >
> > (defmacro aif (test-form then-form &optional else-form)
> >   `(let ((it ,test-form))
> >      (if it ,then-form ,else-form)))
> >
> > (defun select! (pat) ; returns a list of bindings
> >   (print pat)
> >   '((it . (p b a)) (?x . 'b)))
> >
> > (defmacro select-loop (pat &rest keywords-and-forms)
> >   (let ((bind (gensym))
> >         (vars (cons 'it (vars-in pat))))
> >     `(block select-loop
> >        (aif (select! ',pat)
> >             (progn
> >               (let ((binds it) ,@(mapcar #'list vars))
> >                 (declare (special , at vars))
> >                 (loop for ,bind in binds
> >                    do (progn
> >                         (setf it (cdr (assoc 'it ,bind)))
> >                         ,@(mapcar #'(lambda (v) `(setf ,v (cdr (assoc
> ',v ,bind))))
> >                                   vars))
> >                      , at keywords-and-forms)))))))
> >
> > (defmacro defrule (name args &rest body)
> >   `(defmacro ,name ,args
> >      (list 'let (list ,@(mapcar #'(lambda (x) `(list ',x `',,x)) args))
> >        '(declare (special , at args))
> >        ,@(mapcar #'(lambda (x) `'(if (var? ,x) (makunbound ,x))) args)
> >        ,@(mapcar #'(lambda (x) `',x) body))))
> >
> > (defrule ancestor (?x ?y)
> >   (union
> >    (select-loop (p ?x ?y) collect it)
> >    (select-loop (p ?x ?z)
> >                 append (ancestor ?z ?y))))
> >
> > ? (ancestor ?x a)
> >
> > Unhandled exception 10 at 0x28545, context->regs at #xb01641fc
> > Exception occurred while executing foreign code
> >  at compact_dynamic_heap + 965
> > received signal 10; faulting address: 0xd360000
> > ? for help
> > [3422] Clozure CL kernel debugger: ?
> > (G)  Set specified GPR to new value
> > (R)  Show raw GPR/SPR register values
> > (L)  Show Lisp values of tagged registers
> > (F)  Show FPU registers
> > (S)  Find and describe symbol matching specified name
> > (B)  Show backtrace
> > (T)  Show info about current thread
> > (M)  Show memory areas
> > (X)  Exit from this debugger, asserting that any exception was handled
> > (P)  Propagate the exception to another handler (debugger or OS)
> > (K)  Kill Clozure CL process
> > (V)  Show Subversion revision information
> > (?)  Show this help
> > [3422] Clozure CL kernel debugger: B
> > current thread: tcr = 0x2000f0, native thread ID = 0xbe03, interrupts
> enabled
> >
> >
> > Bogus frame 606b40
> > [3422] Clozure CL kernel debugger: L
> > [3422] Clozure CL kernel debugger:
> >
> >
> > Kind regards
> > Taoufik
> >
> > _______________________________________________
> > Openmcl-devel mailing list
> > Openmcl-devel at clozure.com
> > http://clozure.com/mailman/listinfo/openmcl-devel
>
>
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