Should be a lambda expression-LISP

Question

Just one function of my code:

(defun equalprev (x y)
  (cond ((or (atom x) (atom y))
         (if (not (null isLoop))
             t
           ((setq list1 (append list1 (list x)))
            (setq list2 (append list2 (list y)))
            (eql x y))))
        ((equalprev (car x) (car y))
         (equalprev (cdr x) (cdr y)))))

*** - SYSTEM::%EXPAND-FORM: (SETQ LIST1 (APPEND LIST1 (LIST X))) should be a `lambda`
expression
The following restarts are available:
ABORT          :R1      Abort main loop

Any help is appreciated

Please indent things properly.

Inaimathi
– Inaimathi

2012-05-27 02:07:55 +00:00
Commented May 27, 2012 at 2:07 — Inaimathi
– Inaimathi, Commented May 27, 2012 at 2:07

GoZoner · Accepted Answer · 2012-05-26 22:38:07Z

1

The alternate expression for the 'if' expression is ((set! ...) ...). The first position needs to be either a function or a syntactic form. In this case you need progn as:

(progn
  (setq list1 ...)
  (setq list2 ...)
  (eql x y))

answered May 26, 2012 at 22:38

GoZoner

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Comments

leppie · Accepted Answer · 2012-05-27 14:44:01Z

0

Using de Morgan's laws you could construct your condition differently:

(not
 (when (null isLoop)
   (setq list1 (append list1 (list x)))
   (setq list2 (append list2 (list y)))
   (not (eql x y))))

avoiding the use of progn altogether (not that it's a bad thing, but it's often times frowned upon).

edited May 27, 2012 at 14:44

leppie

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answered May 27, 2012 at 12:39

user797257

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