[cells-devel] DEF-C-OUTPUT and hello-world.lisp headscratcher

[Tayssir John Gabbour]

Nevermind, it was answered on usenet. ;)

Tayssir



Tayssir John Gabbour wrote:
> Hi all,
> 
> In cells-test/hello-world.lisp, when running DEF-C-OUTPUT, old-value
> seems always bound to nil. My understanding is it should be bound to the
> previous thing the slot was set to. Am I missing something?
> 
> Sourcecode and repl output below (on SBCL PPC Darwin 0.9.9):
> 
> 
> 
> (use-package :cells)
> (use-package :utils-kt)
> 
> (defmodel computer ()
>   ((happen :cell :ephemeral :initform (c-in nil) :accessor happen)
>    (location :cell t
>              :initform (c? (case (^happen)
>                              (:leave :away)
>                              (:arrive :at-home)
>                              (t .cache))) ;; ie, unchanged
>              :accessor location)
>    (response :cell :ephemeral :initform nil :initarg :response :accessor
> response)))
> 
> (flet ((fmt (name new-value old-value-boundp old-value)
>          (format t "~%~A: ~15A (previously ~:[an unbound ~A~;~A~])"
>                  name new-value old-value-boundp old-value)))
>   (def-c-output response (self new-value old-value old-value-boundp)
>     (fmt "response" new-value old-value-boundp old-value))
>   (def-c-output happen (self new-value old-value old-value-boundp)
>     (fmt "happen  " new-value old-value-boundp old-value))
>   (def-c-output location (self new-value old-value old-value-boundp)
>     (fmt "location" new-value old-value-boundp old-value)))
> 
> 
> (defun hello-world ()
>   (let ((dell
>          (make-be 'computer
>                   :response (c? (bwhen (h (happen self))
>                                   (if (eql (^location) :at-home)
>                                       (case h
>                                         (:knock-knock "who's there?")
>                                         (:world "hello, world."))
>                                       "<silence>"))))))
>     (dotimes (n 2)
>       (setf (happen dell) :knock-knock))
> 
>     (setf (happen dell) :arrive)
>     (setf (happen dell) :knock-knock)
>     (setf (happen dell) :world)
>     (values)))
> 
> 
> 
> ;; At the repl:
> 
> 
> CL-USER> (hello-world)
> 
> ----
> ;;;   instancing object...
> happen  : NIL             (previously an unbound NIL)
> location: NIL             (previously NIL)
> response: NIL             (previously NIL)
> ;;;   instanced object #<COMPUTER {10F59309}>
> ----
> happen  : KNOCK-KNOCK     (previously NIL)
> response: <silence>       (previously NIL)
> happen  : KNOCK-KNOCK     (previously NIL)
> response: <silence>       (previously NIL)
> happen  : ARRIVE          (previously NIL)
> location: AT-HOME         (previously NIL)
> happen  : KNOCK-KNOCK     (previously NIL)
> response: who's there?    (previously NIL)
> happen  : WORLD           (previously NIL)
> response: hello, world.   (previously NIL)
> 
> 
> 
> Thanks,
> Tayssir
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