# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1445362972 -7200
# Node ID ef754d8e1c466a286815e0ee0d73d7801d0fa741
# Parent  8a3994e54ea4b5ce7ee73f955f1f99c6ac3df522
Make the start and end of time instances behave like false values.

diff -r 8a3994e54ea4 -r ef754d8e1c46 imiptools/period.py
--- a/imiptools/period.py	Tue Oct 20 18:39:52 2015 +0200
+++ b/imiptools/period.py	Tue Oct 20 19:42:52 2015 +0200
@@ -79,6 +79,9 @@
     def __rcmp__(self, other):
         return -self.__cmp__(other)
 
+    def __nonzero__(self):
+        return False
+
 class EndOfTime(PointInTime):
 
     "A special value that compares later than other values."
@@ -92,6 +95,9 @@
     def __rcmp__(self, other):
         return -self.__cmp__(other)
 
+    def __nonzero__(self):
+        return False
+
 class PeriodBase:
 
     "A basic period abstraction."