Re: pl-iterator

Hello

I get an error while using next? and %%value on pl-iterators. I have the
following in my kb:

(defconcept component)
(defconcept robot (?c component))

(assert (component arnie))
(assert (robot astrid))
(assert (robot emil))

*************

If I try to run a function using next? and %%value, like so:

(defun foo ()
  (pli:load "/home/magnus/src/powerloom-3.2.15/kbs/peis.plm" nil)
  (pli:change-module "PEIS")

  (let* ((iter (pli:s-retrieve "all (component ?x)" stella::null-string
                   stella::null-string)))
    (loop while (stella::next? iter) do
     (print (stella::%%value iter)))))

************

I get the following error:

Type-error in KERNEL::OBJECT-NOT-CONS-ERROR-HANDLER:
   |i|/PLI/@PL-ITERATOR is not of type CONS
   [Condition of type TYPE-ERROR]

Restarts:
  0: [ABORT-REQUEST] Abort handling SLIME request.
  1: [ABORT] Return to Top-Level.

Backtrace:
  0: (FOO)

*************

Now, If I listify the iterator, e.g.:

(defun bar ()
  (pli:load "/home/magnus/src/powerloom-3.2.15/kbs/peis.plm" nil)
  (pli:change-module "PEIS")

  (let* ((iter (pli:s-retrieve "all (component ?x)" stella::null-string
                   stella::null-string)))
    (pli:listify iter)))

***************

I get a correct output:

|l|(|i|ARNIE |i|EMIL |i|ASTRID)

*************

I could of course return this result as a string, massage it a bit (remove
the prefixes etc), and be happily on my way. Though I am curious about what
I do wrong in this case? Since the example-code diden't manage to loop over
the iterator, I am sure that either the example code is missing some vital
part, or that I am missing some obvious part myself.

I have tried both the current stable version of PowerLoom, as well as the
snapshot found on the website.

Kind regards,
-- 
Magnus Malm

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