I'm trying to implement a poset class in sagex. The following output indicates
to me that __cmp__ gets called on the sagex class no matter what. This means
that partial ordering cannot be implemented in sagex (rather, it can, but can't
take advantage of the comparison overloading that python offers).
I'm working with Bruhat ordering on permutations, but I've pared the example
down to the following:
%sagex
cdef class po_sagex:
def __init__(self):
pass
def __le__(self, other):
return False
sage: a = po_sagex()
sage: b = po_sagex()
sage: print a <= b
True
sage: print b <= a
False
(note -- sometimes, True and False switch places in this example)
class po_python:
def __init__(self):
pass
def __le__(self, other):
return False
sage: c = po_python()
sage: d = po_python()
sage: print c <= d
False
sage: print d <= c
False
To work around this, I tried to implement a robust __cmp__ which returns None
if the objects are incomparable, and no dice -- it barfs if __cmp__ doesn't
return an integer.
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