X-Git-Url: https://svn.cri.ensmp.fr/git/linpy.git/blobdiff_plain/d1592edb29b12dafe5c0d0698310b98b4915cf26..0e724482ff4e0713a0ec55c1cd3c2293ece5ed47:/linpy/domains.py

diff --git a/linpy/domains.py b/linpy/domains.py
index da0ea97..4b3e982 100644
--- a/linpy/domains.py
+++ b/linpy/domains.py
@@ -340,35 +340,39 @@ class Domain(GeometricObject):
         Return the union of two or more domains as a new domain. As an
         alternative, function Or() can be used.
         """
-        if len(others) == 0:
-            return self
-        symbols = self._xsymbols((self,) + others)
-        islset1 = self._toislset(self.polyhedra, symbols)
+        result = self
         for other in others:
-            islset2 = other._toislset(other.polyhedra, symbols)
-            islset1 = libisl.isl_set_union(islset1, islset2)
-        return self._fromislset(islset1, symbols)
+            result |= other
+        return result
 
     def __or__(self, other):
-        return self.union(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_union(islset1, islset2)
+            return self._fromislset(islset, symbols)
+        return NotImplemented
     __or__.__doc__ = union.__doc__
 
     def __add__(self, other):
-        return self.union(other)
+        return self | other
     __add__.__doc__ = union.__doc__
 
     def difference(self, other):
         """
         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):
@@ -387,7 +391,10 @@ class Domain(GeometricObject):
         islset = libisl.isl_set_lexmax(islset)
         return self._fromislset(islset, self.symbols)
 
-    _RE_COORDINATE = re.compile(r'\((?P<num>\-?\d+)\)(/(?P<den>\d+))?')
+    if islhelper.isl_version >= '0.13':
+        _RE_COORDINATE = re.compile(r'\((?P<num>\-?\d+)\)(/(?P<den>\d+))?')
+    else:
+        _RE_COORDINATE = None
 
     def vertices(self):
         """
@@ -405,7 +412,7 @@ class Domain(GeometricObject):
         for vertex in vertices:
             expr = libisl.isl_vertex_get_expr(vertex)
             coordinates = []
-            if islhelper.isl_version < '0.13':
+            if self._RE_COORDINATE is None:
                 constraints = islhelper.isl_basic_set_constraints(expr)
                 for constraint in constraints:
                     constant = libisl.isl_constraint_get_constant_val(constraint)