unstable sort [ci skip]

* array.c (rb_ary_sort_bang, rb_ary_sort, rb_ary_sort_by_bang):
  [DOC] describe that sort may not be stable.
* enum.c (enum_sort, enum_sort_by): ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56413 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 8 insertions, 0 deletions

diff --git a/array.c b/array.c
index 476b1c4d66..55cdd9d7e3 100644
--- a/array.c
+++ b/array.c
@@ -2436,6 +2436,9 @@ sort_2(const void *ap, const void *bp, void *dummy)
  *  an integer less than 0 when +b+ follows +a+, +0+ when +a+ and +b+
  *  are equivalent, or an integer greater than 0 when +a+ follows +b+.
  *
+ *  The result is not guaranteed as stable.  When comparison of two
+ *  elements returns +0+, the order of the elements is unpredictable.
+ *
  *  See also Enumerable#sort_by.
  *
  *     a = [ "d", "a", "e", "c", "b" ]
@@ -2517,6 +2520,8 @@ rb_ary_sort_bang(VALUE ary)
  *  an integer less than 0 when +b+ follows +a+, +0+ when +a+ and +b+
  *  are equivalent, or an integer greater than 0 when +a+ follows +b+.
  *
+ *  The result is not guaranteed as stable.  When comparison of two
+ *  elements returns +0+, the order of the elements is unpredictable.
  *
  *  See also Enumerable#sort_by.
  *
@@ -2674,6 +2679,9 @@ sort_by_i(RB_BLOCK_CALL_FUNC_ARGLIST(i, dummy))
  *  Sorts +self+ in place using a set of keys generated by mapping the
  *  values in +self+ through the given block.
  *
+ *  The result is not guaranteed as stable.  When two keys are equal,
+ *  the order of the corresponding elements is unpredictable.
+ *
  *  If no block is given, an Enumerator is returned instead.
  *
  */