[cl-utilities-cvs] CVS cl-utilities/doc

[pscott]

Update of /project/cl-utilities/cvsroot/cl-utilities/doc
In directory clnet:/tmp/cvs-serv24065/doc

Modified Files:
	split-sequence.html 
Log Message:
Added implementation notes explaining the abysmal performance on lists.


--- /project/cl-utilities/cvsroot/cl-utilities/doc/split-sequence.html	2006/05/03 01:33:28	1.3
+++ /project/cl-utilities/cvsroot/cl-utilities/doc/split-sequence.html	2006/05/03 01:46:54	1.4
@@ -78,11 +78,28 @@
 me</a> so we can get it straightened out.</p>
 
 <p>The implementation itself is mature and well tested, and it is
-widely used. Efficiency probably isn't what it could be with some type
-declarations, but the code is striaghtforward and should be fast
-enough. If it isn't fast enough for <i>you</i>, feel free to modify
-it, or even just complain about it on the mailing list---something
-might get done.</p>
+widely used. The code should be fast enough for most people, but be
+warned: it was written with vectors in mind, with list manipulation as
+an afterthought. It does a lot of things that are quick on vectors but
+slow on lists, and this can result in many orders of magnitude
+slowdown in list benchmarks versus code written for lists. If this is
+a problem for you, it should be straightforward to write your own,
+such as the (more limited, not API compatible) example function given
+by Szymon in <a
+href="http://common-lisp.net/pipermail/cl-utilities-devel/2006-May/000011.html">this
+mailing list post</a>:</p>
+
+<p><pre>
+(defun split-list-if (test list &aux (start list) (end list))
+  (loop while (and end (setq start (member-if-not test end)))
+	collect (ldiff start (setq end (member-if test start)))))
+</pre></p>
+
+<p>If this is an issue for enough people, I could optimize the code
+and fix this problem. I'm reluctant to do that, however, since the
+code works and is tested. It's usually more important to be correct
+and non-buggy than to be fast, and I have been known to introduce
+bugs.</p>
 
 <p class="footer"><hr><a href="index.html">Manual Index</a></p>