# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@fb.com>
# Date 1412625156 25200
# Node ID c1fd827e1ae0614a02fd8a7e34ce0b7f9bf32b46
# Parent  7f97cb12782f8f9c56317d033bb64de1e663735c
generatorset: implement first and last methods

diff -r 7f97cb12782f -r c1fd827e1ae0 mercurial/revset.py
--- a/mercurial/revset.py	Mon Oct 06 11:57:59 2014 -0700
+++ b/mercurial/revset.py	Mon Oct 06 12:52:36 2014 -0700
@@ -2767,6 +2767,34 @@
     def isdescending(self):
         return not self._ascending
 
+    def first(self):
+        if self._ascending:
+            it = self.fastasc
+        else:
+            it = self.fastdesc
+        if it is None:
+            # we need to consume all and try again
+            for x in self._consumegen():
+                pass
+            return self.first()
+        if self:
+            return it.next()
+        return None
+
+    def last(self):
+        if self._ascending:
+            it = self.fastdesc
+        else:
+            it = self.fastasc
+        if it is None:
+            # we need to consume all and try again
+            for x in self._consumegen():
+                pass
+            return self.first()
+        if self:
+            return it.next()
+        return None
+
 def spanset(repo, start=None, end=None):
     """factory function to dispatch between fullreposet and actual spanset