Trac #23886: py3: no more cmp between sets

as a step to py3

URL: https://trac.sagemath.org/23886
Reported by: chapoton
Ticket author(s): Frédéric Chapoton
Reviewer(s): Travis Scrimshaw

src/sage/sets/set.py

@@ -45,6 +45,7 @@
 from sage.structure.category_object import CategoryObject
 from sage.structure.element import Element
 from sage.structure.parent import Parent, Set_generic
+from sage.structure.richcmp import richcmp_method, richcmp, rich_to_bool
 
 from sage.categories.sets_cat import Sets
 from sage.categories.enumerated_sets import EnumeratedSets
@@ -225,6 +226,7 @@ def is_Set(x):
     """
     return isinstance(x, Set_generic)
 
+@richcmp_method
 class Set_object(Set_generic):
     r"""
     A set attached to an almost arbitrary object.
@@ -391,13 +393,13 @@ def __contains__(self, x):
         """
         return x in self.__object
 
-    def __cmp__(self, right):
+    def __richcmp__(self, right, op):
         r"""
         Compare ``self`` and ``right``.
 
-        If right is not a :class:`Set_object` compare types.  If ``right`` is
-        also a :class:`Set_object`, returns comparison on the underlying
-        objects.
+        If ``right`` is not a :class:`Set_object`, return ``NotImplemented``.
+        If ``right`` is also a :class:`Set_object`, returns comparison
+        on the underlying objects.
 
         .. NOTE::
 
@@ -422,8 +424,8 @@ def __cmp__(self, right):
             True or False
         """
         if not isinstance(right, Set_object):
-            return cmp(type(self), type(right))
-        return cmp(self.__object, right.__object)
+            return NotImplemented
+        return richcmp(self.__object, right.__object, op)
 
     def union(self, X):
         """
@@ -921,7 +923,7 @@ def __hash__(self):
         """
         return hash(self.frozenset())
 
-    def __cmp__(self, other):
+    def __richcmp__(self, other, op):
         """
         Compare the sets ``self`` and ``other``.
 
@@ -935,12 +937,11 @@ def __cmp__(self, other):
             sage: Set(QQ) == Set(ZZ)
             False
         """
-        if isinstance(other, Set_object_enumerated):
-            if self.set() == other.set():
-                return 0
-            return -1
-        else:
-            return Set_object.__cmp__(self, other)
+        if not isinstance(other, Set_object_enumerated):
+            return NotImplemented
+        if self.set() == other.set():
+            return rich_to_bool(op, 0)
+        return rich_to_bool(op, -1)
 
     def issubset(self, other):
         r"""
@@ -1208,7 +1209,7 @@ def is_finite(self):
         """
         return self._X.is_finite() and self._Y.is_finite()
 
-    def __cmp__(self, right):
+    def __richcmp__(self, right, op):
         r"""
         Try to compare ``self`` and ``right``.
 
@@ -1237,13 +1238,13 @@ def __cmp__(self, right):
             False
         """
         if not is_Set(right):
-            return -1
+            return rich_to_bool(op, -1)
         if not isinstance(right, Set_object_union):
-            return -1
+            return rich_to_bool(op, -1)
         if self._X == right._X and self._Y == right._Y or \
            self._X == right._Y and self._Y == right._X:
-            return 0
-        return -1
+            return rich_to_bool(op, 0)
+        return rich_to_bool(op, -1)
 
     def __iter__(self):
         """
@@ -1342,7 +1343,7 @@ def is_finite(self):
             return True
         raise NotImplementedError
 
-    def __cmp__(self, right):
+    def __richcmp__(self, right, op):
         r"""
         Try to compare ``self`` and ``right``.
 
@@ -1371,13 +1372,13 @@ def __cmp__(self, right):
             False
         """
         if not is_Set(right):
-            return -1
+            return rich_to_bool(op, -1)
         if not isinstance(right, Set_object_intersection):
-            return -1
+            return rich_to_bool(op, -1)
         if self._X == right._X and self._Y == right._Y or \
            self._X == right._Y and self._Y == right._X:
-            return 0
-        return -1
+            return rich_to_bool(op, 0)
+        return rich_to_bool(op, -1)
 
     def __iter__(self):
         """
@@ -1484,7 +1485,7 @@ def is_finite(self):
             return False
         raise NotImplementedError
 
-    def __cmp__(self, right):
+    def __richcmp__(self, right, op):
         r"""
         Try to compare ``self`` and ``right``.
 
@@ -1517,12 +1518,12 @@ def __cmp__(self, right):
             True
         """
         if not is_Set(right):
-            return -1
+            return rich_to_bool(op, -1)
         if not isinstance(right, Set_object_difference):
-            return -1
+            return rich_to_bool(op, -1)
         if self._X == right._X and self._Y == right._Y:
-            return 0
-        return -1
+            return rich_to_bool(op, 0)
+        return rich_to_bool(op, -1)
 
     def __iter__(self):
         """
@@ -1621,7 +1622,7 @@ def is_finite(self):
             return False
         raise NotImplementedError
 
-    def __cmp__(self, right):
+    def __richcmp__(self, right, op):
         r"""
         Try to compare ``self`` and ``right``.
 
@@ -1644,13 +1645,13 @@ def __cmp__(self, right):
 
         """
         if not is_Set(right):
-            return -1
+            return rich_to_bool(op, -1)
         if not isinstance(right, Set_object_symmetric_difference):
-            return -1
+            return rich_to_bool(op, -1)
         if self._X == right._X and self._Y == right._Y or \
            self._X == right._Y and self._Y == right._X:
-            return 0
-        return -1
+            return rich_to_bool(op, 0)
+        return rich_to_bool(op, -1)
 
     def __iter__(self):
         """