Re: stability of sort()?

Message-ID: <20010525224019.B86445@plum.flirble.org>

p4raw-id: //depot/perl@10215

diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod
index c2b9f39..2fa645d 100644 (file)
--- a/pod/perlfunc.pod
+++ b/pod/perlfunc.pod
@@ -4291,6 +4291,12 @@ loop control operators described in L<perlsyn> or with C<goto>.
 When C<use locale> is in effect, C<sort LIST> sorts LIST according to the
 current collation locale.  See L<perllocale>.
 
+Perl does B<not> guarantee that sort is stable.  (In a I<stable> sort the
+relative order is preserved for elements where the sort comparison used
+returns that they are equal.)  5.7 happens to use a mergesort, which is
+stable, but 5.6 and earlier used quicksort, which is not.  However, do not
+assume that future perls will continue to use a stable sort such as mergesort.
+
 Examples:
 
     # sort lexically