Cleaner implementation of Domain.__sub__()

[linpy.git] / linpy / domains.py

diff --git a/linpy/domains.py b/linpy/domains.py
index da0ea97..9fdc7d5 100644 (file)
--- 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):