X-Git-Url: https://svn.cri.ensmp.fr/git/linpy.git/blobdiff_plain/3c9e6c7cd0631426b79a28c9b15f8d40e01cec4c..62fbaa7984d8035cccc97555f1de3188e280e475:/linpy/domains.py?ds=inline

diff --git a/linpy/domains.py b/linpy/domains.py
index 57c08ba..9fdc7d5 100644
--- a/linpy/domains.py
+++ b/linpy/domains.py
@@ -363,14 +363,16 @@ class Domain(GeometricObject):
         """
         Return the difference of two domains as a new domain.
         """
-        symbols = self._xsymbols([self, other])
-        islset1 = self._toislset(self.polyhedra, symbols)
-        islset2 = other._toislset(other.polyhedra, symbols)
-        islset = libisl.isl_set_subtract(islset1, islset2)
-        return self._fromislset(islset, symbols)
+        return self - other
 
     def __sub__(self, other):
-        return self.difference(other)
+        if isinstance(other, Domain):
+            symbols = self._xsymbols([self, other])
+            islset1 = self._toislset(self.polyhedra, symbols)
+            islset2 = other._toislset(other.polyhedra, symbols)
+            islset = libisl.isl_set_subtract(islset1, islset2)
+            return self._fromislset(islset, symbols)
+        return NotImplemented
     __sub__.__doc__ = difference.__doc__
 
     def lexmin(self):