:test-not test-not :test-not-p test-not-p))
(return index)))))
+;; TODO: need to support &key from-end
+(defun position-if (predicate sequence
+ &key key (start 0) end)
+ ;; TODO: Implement START and END efficiently for all the sequence
+ ;; functions.
+ (let ((end (or end (length sequence))))
+ (do-sequence (x sequence index)
+ (when (and (<= start index)
+ (< index end)
+ (funcall predicate (if key (funcall key x) x)))
+ (return index)))))
+
+(defun position-if-not (predicate sequence
+ &key key (start 0) end)
+ (position-if (complement predicate) sequence :key key :start start :end end))
+
(defun remove (x seq &key key (test #'eql testp) (test-not #'eql test-not-p))
(cond
((null seq)
((= j b) new)
(aset new i (aref seq j)))))
(t (not-seq-error seq))))
+
+(defun copy-seq (sequence)
+ (subseq sequence 0))
+
+
+;;; Reduce (based on SBCL's version)
+
+(defun reduce (function sequence &key key from-end (start 0) end (initial-value nil ivp))
+ (let ((key (or key #'identity))
+ (end (or end (length sequence))))
+ (if (= end start)
+ (if ivp initial-value (funcall function))
+ (macrolet ((reduce-list (function sequence key start end initial-value ivp from-end)
+ `(let ((sequence
+ ,(if from-end
+ `(reverse (nthcdr ,start ,sequence))
+ `(nthcdr ,start ,sequence))))
+ (do ((count (if ,ivp ,start (1+ ,start))
+ (1+ count))
+ (sequence (if ,ivp sequence (cdr sequence))
+ (cdr sequence))
+ (value (if ,ivp ,initial-value (funcall ,key (car sequence)))
+ ,(if from-end
+ `(funcall ,function (funcall ,key (car sequence)) value)
+ `(funcall ,function value (funcall ,key (car sequence))))))
+ ((>= count ,end) value)))))
+ (if from-end
+ (reduce-list function sequence key start end initial-value ivp t)
+ (reduce-list function sequence key start end initial-value ivp nil))))))