(defun uniquify-sorted-list (list &key (key #'identity) (test #'eql))
(loop for element in list
for element-key = (funcall key element)
for last-element-key = (load-time-value (gensym))
then element-key
unless (funcall test element-key last-element-key)
collect element))
Gauche Scheme:
(define (destutter seq :optional (test equal?) (key values))
(if (or (null? seq) (null? (cdr seq)))
seq
(let ((ab (take seq 2)))
(if (apply test (map key ab))
(destutter (cdr seq) test key)
(cons (car ab) (destutter (cdr seq) test key))))))
(destutter '(0 0 1 2 3 3 3 4 5))
===>
(0 1 2 3 4 5)
(destutter '(0 0 2 3 5 7 6 8) eq? odd?)
===>
(2 7 8)
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