On 3/18/2010 5:48 PM, Nick Coghlan wrote:
Mark Dickinson wrote:
Could everyone live with making float<->Decimal comparisons raise an
exception in 2.7?
I could, with the caveat that *if* this causes problems for real world
code, then changing it to produce the correct answer (as per your patch)
should be applied as a bug fix in both 2.7 and 3.2.
Note that even in Py3k there are some fairly serious weirdnesses kicking
around due to the intransitive nature of numeric equality though:
from decimal import Decimal as dec
set((1, 1.0, dec("1.0")))
{1}
set((1.0, dec("1.0")))
{1.0, Decimal('1.0')}
d = {}
from decimal import Decimal as dec
d[1] = d[1.0] = d[dec("1.0")] = 42
d
{1: 42}
d[1.0] = d[dec("1.0")] = 42
d
{1: 42}
del d[1]
d[1.0] = d[dec("1.0")] = 42
d
{1.0: 42, Decimal('1.0'): 42}
When there is a clear, correct way (based on Decimal.from_float) to make
numeric comparison behave in accordance with the rules of mathematics,
do we really want to preserve strange, unintuitive behaviour like the above?
I would still strongly prefer that equality intransitivity be fixed one
way or another (I suggested two on the tracker). The many ways it makes
sets misbehave was discussed in both of
http://mail.python.org/pipermail/python-list/2008-September/508859.html
http://bugs.python.org/issue4087
Terry Jan Reedy
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