[alexandria-devel] Re: length=1

[Attila Lendvai]

>  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 at 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>))