Mark Dickinson <[email protected]> added the comment:
> I think hash(Decimal("snan")) should also succeed
On second thoughts, this would be bad, since it would lead to unpredictable
results for sets of dicts containing a signaling nan:
>>> from decimal import Decimal
[69536 refs]
>>> s = Decimal('snan'); h = hash(s)
[69551 refs]
>>> {s, h+1} # can put most integers into a set with an sNaN
{Decimal('sNaN'), 373955814}
[69561 refs]
>>> {s, h} # but not if that integer hashes equal to the sNaN...
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Users/dickinsm/python/svn/py3k/Lib/decimal.py", line 864, in __eq__
ans = self._check_nans(other, context)
File "/Users/dickinsm/python/svn/py3k/Lib/decimal.py", line 746, in
_check_nans
self)
File "/Users/dickinsm/python/svn/py3k/Lib/decimal.py", line 3842, in
_raise_error
raise error(explanation)
decimal.InvalidOperation: sNaN
[69698 refs]
So if __eq__ with an sNaN raises an exception, there's little choice but to
prohibit putting sNaNs into sets and dicts, and the obvious way to do this is
to make __hash__ raise too.
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Python tracker <[email protected]>
<http://bugs.python.org/issue7279>
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