2257 class _orderedsetmixin(object):

  2258     """Mixin class with utility methods for smartsets

  2259 

  2260     This should be extended by smartsets which have the isascending(),

  2261     isdescending() and reverse() methods"""

  2262 

  2263     def _first(self):

  2264         """return the first revision in the set"""

  2265         for r in self:

  2266             return r

  2267         return None

  2268 

  2269     def _last(self):

  2270         """return the last revision in the set"""

  2271         self.reverse()

  2272         m = self._first()

  2273         self.reverse()

  2274         return m

  2275 

  2276     def min(self):

  2277         """return the smallest element in the set"""

  2278         if self.isascending():

  2279             return self._first()

  2280         return self._last()

  2281 

  2282     def max(self):

  2283         """return the largest element in the set"""

  2284         if self.isascending():

  2285             return self._last()

  2286         return self._first()

  2287