CODEWITHSUNDEEP
loopslispcommon-lisp
user1205371
user1205371

Reputation:

Lisp Help | Error: Duplicate binding in LOOP : (result)

(defmethod! expand-t-setclass (pcset &optional (n 12))
  :icon *PC_ICON*
  :doc "
Given any member of a t-setclass, lists every member of that t-setclass.
The optional parameter N can be used to set the number of equal steps per
octave to something other than the default of 12.

Will tolerate integers out of the mod-N range in PCSET."
  :initvals '((1 3 4) 12)
  :indoc '("pcset or list of them"
           "modulus of the pc space")
  (if (listp (first pcset))
    (expand-t-setclasses pcset)
    (let ((t-prime (t-primeform pcset n)))
      (loop with result = nil
            repeat n
            for x-pcset = pcset then (xpose x-pcset 1 n)
            unless (member x-pcset result) collect x-pcset into result
            finally return result))))


(defmethod! expand-t-setclasses (pcset &optional (n 12))
  (loop for item in pcset collect (expand-t-setclass item n)))

;-----

I am not too familiar with Lisp in general, and am trying to find the bug that casues this error:

ERROR: Duplicate Binding in LOOP: (result)

Upvotes: 0

Views: 201

Answers (1)

Rainer Joswig
Rainer Joswig

Reputation: 139261

You have two forms in the LOOP introducing a variable RESULT.

WITH result = nil

and

COLLECT ... INTO result

Both above create a variable binding.

I would replace the COLLECT with a form which pushes the item to the RESULT list.

(loop ...
      collect item into foo
      ...
      finally (return foo))

into

(loop with foo = nil
      ...
      (push item foo)
      ...
      finally (return (reverse foo)))

You have another error:

FINALLY RETURN result

The LOOP syntax does not support that. FINALLY expects a compound form.

Replace it with:

FINALLY (return result)

RETURN is a defined macro in Common Lisp.

Upvotes: 1

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