On Dec 4, 2005, at 6:25 AM, Gavin Mendel-Gleason wrote:

Hello,

I had the same problem and I don't think it was intentional. I think it is because it is mostly used for deterministic code.

I had not given too much thought indeed to non-determinism. As per the actual copy operations, if people are interested in deep copy operations then they can be added, but I would keep them alongside the shallow copy operations.

You don't really need to copy everything anyhow if you are using a standard unification algorithm since changes should be monotonic. You just need to branch. You can effect this with the following change:

(defun make-shared-environment (env) (make-environment :frames (environment-frames env)))

=>

(defun make-shared-environment (env) (make-environment :frames (cons (make-frame) (environment-frames env))))

Or some alteration that is similar that branches the environments at choice points.

MAKE-SHARED-ENVIRONMENT was provided as is because the augmentation of the environment (branches) was supposed to be done by other functions. But maybe ensuring that the extra frame is there is a good idea.

Cheers -- Marco

On 12/4/05, norman werner norman.werner@web.de wrote:

...

Hello

While writing a library with prolog like capabilities on top of cl-unification and a home brewn nondeterministic library I need a way to copy environments.

There is a (internal) function copy-env in cl-unification. So I exported it. The problem is that this function returns a new environment which actually still shares objects with its original argument.

Is this intentional? If not I propose the following (code will certainly contain bug, because i write it from memory only)

(defun copy-env (e) (make-environment :frames (mapcar #'copy-frame (frames e))))

(defun copy-frame (f) (make-frame :bindings (mapcar #'copy-binding (binding f))))

(defun copy-binding (b) (mapcar #'(lambda (cell) (cons (car cell) (cdr cell))) b))

Norman ______________________________________________________________ Verschicken Sie romantische, coole und witzige Bilder per SMS! Jetzt bei WEB.DE FreeMail: http://f.web.de/?mc=021193

---

cl-unification-devel site list cl-unification-devel@common-lisp.net http://common-lisp.net/mailman/listinfo/cl-unification-devel

---

cl-unification-devel site list cl-unification-devel@common-lisp.net http://common-lisp.net/mailman/listinfo/cl-unification-devel

-- Marco Antoniotti http://bioinformatics.nyu.edu/~marcoxa NYU Courant Bioinformatics Group tel. +1 - 212 - 998 3488 715 Broadway 10th FL fax. +1 - 212 - 998 3484 New York, NY, 10003, U.S.A.