Exporting LENGTH=1 and LENGTH=2 may be debateable, the only use case is the one Andreas Fuchs mentioned, i.e. as arguments to FIND-IF &c.
i've got this recorded and ready to be pushed. unless soemone has additional comments, i'll push it eventually. (note: i've not included the debatable length=1/2) -- attila Sat Mar 1 10:01:54 CET 2008 attila.lendvai@gmail.com * Added length>, WARNING: renamed sequence-of-length-p to length= (Based on code by Tobias C. Rittweiler) diff -rN -u old-alexandria/package.lisp new-alexandria/package.lisp --- old-alexandria/package.lisp 2008-03-01 10:02:20.000000000 +0100 +++ new-alexandria/package.lisp 2008-03-01 10:02:21.000000000 +0100 @@ -98,7 +98,8 @@ #:random-elt #:removef #:rotate - #:sequence-of-length-p + #:length= + #:length> #:shuffle #:starts-with #:starts-with-subseq diff -rN -u old-alexandria/sequences.lisp new-alexandria/sequences.lisp --- old-alexandria/sequences.lisp 2008-03-01 10:02:20.000000000 +0100 +++ new-alexandria/sequences.lisp 2008-03-01 10:02:21.000000000 +0100 @@ -1,5 +1,9 @@ (in-package :alexandria) +;; Make these inlinable by declaiming them INLINE here and some of them +;; NOTINLINE at the end of the file. +(declaim (inline copy-sequence length= length>)) + (defun rotate-tail-to-head (sequence n) (declare (type (integer 1) n)) (if (listp sequence) @@ -113,9 +117,12 @@ (list (null sequence)) (sequence (zerop (length sequence))))) -(defun sequence-of-length-p (sequence length) +(defun length= (sequence length) "Return true if SEQUENCE is a sequence of length LENGTH. Signals an error if SEQUENCE is not a sequence. Returns FALSE for circular lists." + (declare (type array-index length) + (inline length) + (optimize speed)) (etypecase sequence (null (zerop length)) @@ -123,11 +130,32 @@ (let ((n (1- length))) (unless (minusp n) (let ((tail (nthcdr n sequence))) - (and tail (null (cdr tail))))))) + (and tail + (null (cdr tail))))))) + (simple-vector + (= length (length sequence))) + (vector + (= length (length sequence))) (sequence (= length (length sequence))))) -(declaim (inline copy-sequence)) +(defun length> (sequence n) + "Returns non-nil if (> (length SEQUENCE) N)." + (declare (inline length) + (optimize speed) + (type array-index n)) + (etypecase sequence + (list + (and (>= n 0) + (nthcdr n sequence) + t)) + (simple-vector + (> (length sequence) n)) + (vector + (> (length sequence) n)) + (sequence + (> (length sequence) n)))) + (defun copy-sequence (type sequence) "Returns a fresh sequence of TYPE, which has the same elements as SEQUENCE." @@ -395,3 +423,5 @@ (setf (bit mask i) 0)))))) (derange start size) sequence))) + +(declaim (notinline length= length>))