from sage.structure.richcmp import richcmp_by_eq_and_lt,richcmp_method
@richcmp_method
class A(object):
def __init__(self,x):
self._x = x
__richcmp__ = richcmp_by_eq_and_lt("_eq","_lt")
def _eq(self,other):
if type(other)!=type(self):
#other knows how to do the comparison
return other.__eq__(self)
return self._x == other._x
def _lt(self,other):
return self._x<other._x
def __repr__(self):
return "A %r" %self._x
@richcmp_method
class B(A):
#I can do comparison myself
def __init__(self,x,extra):
A.__init__(self,x)
__richcmp__ = richcmp_by_eq_and_lt("_eq","_lt")
def _eq(self,other):
print("hello")
return self._x == other._x
def _lt(self,other):
return self._x<other._x
def __repr__(self):
return "B %r" %self._x
There you go:
sage: A(1) == B(1,"a")
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call last)
<ipython-input-4-f5a54e86b883> in <module>()
----> 1 A(Integer(1)) == B(Integer(1),"a")
/home/simon/sage/src/sage/structure/richcmp.pyx in
sage.structure.richcmp.slot_tp_richcompare
(build/cythonized/sage/structure/richcmp.c:1459)()
110 Function to put in the ``tp_richcompare`` slot.
111 """
--> 112 return self.__richcmp__(other, op)
113
114
/home/simon/sage/src/sage/structure/richcmp.pyx in
sage.structure.richcmp.richcmp_by_eq_and_lt.richcmp
(build/cythonized/sage/structure/richcmp.c:2178)()
317 if equal_types:
318 other_eq = getattr(other, eq_attr)
--> 319 if other_eq(self):
320 return rich_to_bool(op, 0)
321 if op == Py_EQ:
/home/simon/sage/src/sage/modules/bug.py in _eq(self, other)
10 if type(other)!=type(self):
11 #other knows how to do the comparison
---> 12 return other.__eq__(self)
13 return self._x == other._x
14 def _lt(self,other):
... last 3 frames repeated, from the frame below ...
/home/simon/sage/src/sage/structure/richcmp.pyx in
sage.structure.richcmp.slot_tp_richcompare
(build/cythonized/sage/structure/richcmp.c:1459)()
110 Function to put in the ``tp_richcompare`` slot.
111 """
--> 112 return self.__richcmp__(other, op)
113
114
RuntimeError: maximum recursion depth exceeded while calling a Python object
Enter code here...
This is unexpected but we know what to do
from sage.structure.richcmp import richcmp_by_eq_and_lt,richcmp_method
@richcmp_method
class A(object):
def __init__(self,x):
self._x = x
__richcmp__ = richcmp_by_eq_and_lt("_eq","_lt")
def _eq(self,other):
if type(other)!=type(self):
#other knows how to do the comparison
return self.__eq__(other)
return self._x == other._x
def _lt(self,other):
return self._x<other._x
def __repr__(self):
return "A %r" %self._x
@richcmp_method
class B(A):
#I can do comparison myself
def __init__(self,x,extra):
A.__init__(self,x)
__richcmp__ = richcmp_by_eq_and_lt("_eq","_lt")
def _eq(self,other):
print("hello")
return self._x == other._x
def _lt(self,other):
return self._x<other._x
def __repr__(self):
return "B %r" %self._x
### reloading attached file bug.py modified at 12:00:42 ###
sage: A(1) == B(1,"a")
hello
True
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