# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@fb.com>
# Date 2014-10-01 03:26:34
# Node ID 6877ba8d85ff3ff2f075f4353f21af91f7a64014
# Parent  557749fea14ab37dbf9fcec089cf1895e8e0d1e5

abstractsmartset: document the `fastasc` and `fastdesc` attributes/methods

See the in-line documentation for details. (This is the beginning of a massive
overhaul of revset).

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -2218,6 +2218,14 @@ class abstractsmartset(object):
         """iterate the set in the order it is supposed to be iterated"""
         raise NotImplementedError()
 
+    # Attributes containing a function to perform a fast iteration in a given
+    # direction. A smartset can have none, one, or both defined.
+    #
+    # Default value is None instead of a function returning None to avoid
+    # initializing an iterator just for testing if a fast method exists.
+    fastasc = None
+    fastdesc = None
+
     def isascending(self):
         """True if the set will iterate in ascending order"""
         raise NotImplementedError()