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works fine:

(rnd-replace '(123) '(1 2 3 4))

=> (1 2 3 123)

 

don't work ... why?

(rnd-replace '(123) '(1 2 3 4) :exclude '(2 3))

=> 

> Error: The value 1 is not of the expected type list.
> While executing: pos-rep, in process Listener-1(6).
> Type cmd-. to abort, cmd-\ for a list of available restarts.
> Type :? for other options.

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section and exclude works with lists not on a list.

 

Arguments and Values:

 

section            an integer or a list of integers. Selected list or lists to process. The default is NIL.

exclude            an integer or a list of integers. Excluded list or lists from process. The default is NIL.

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i needed something like that..

regards

andré

(defun rnd-replace/user (item sequence &key (exclude 'nil))
    (loop for i in sequence
      with val
      with pos = (position (car (loop 
                                  do (setf val (nth (random (length sequence)) sequence))
                                  when (null (member val exclude))
                                  collect val into bag
                                  when (= (length bag) 1)
                                  do (return bag))) 
                           sequence)
      for cnt = 0 then (incf cnt)
      when (= cnt pos)
      collect (rnd-pick item)
      else collect i))

(rnd-replace/user '(123 987) '(1 2 3 4 5) :exclude '(1 5))

 

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