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Error with LET:
- To: email@example.com
- Subject: Error with LET:
- From: Cory Serratore <firstname.lastname@example.org>
- Date: Wed, 13 Jul 1994 11:27:38 -0400
I'm sorry that I don't have the exact error message, as I'm currently
posting from my unix account on campus, but I couldn't get CLISP
to accept the following code that akcl seems OK with.
(defun get-mgu (p1 p2 o)
"This function takes as input a pair of terms p1 p2 and a substitution
set o and returns a Most General Unifier (MGU) of the pair IF they are
unifiable. Otherwise, it returns nil."
(let ((po1 nil) ; Apply substitution o
(po2 nil) ; Apply substitution o
(vterm nil)) ; unifier for Diff
(setq po1 (apply-sub o p1))
(setq po2 (apply-sub o p2))
(setq Diff (get-disagreement-set po1 po2))
(setq vterm (set-vterm Diff))
(if (equal po1 po2)
o ; Return MGU
(if (null vterm) ; So is not unifiable
nil ; repeat with composition of vt and o
(get-mgu po1 po2 (composition (list vterm) o))))
The error message had something to do with a bad variable assignment in my
LET statement. This code includes a number of functions that I have defined
elsewhere, so those aren't important, but is there a problem with my
LET structure? Am I using a system variable or something, or is this just
a case where CLISP is not 100% compatible with Common Lisp (or is akcl not
If this isn't enough to go on, I will post the exact error message later.
Any help appreciated.