[Python-ideas] Make max() stable

[David Mertz]

Oh yeah, this has been my bête noire for a long time.  I think I first
mentioned this in 2003 at:

  https://mail.python.org/pipermail/python-list/2003-March/205446.html

Then later in an IBM developerWorks article in 2005:

  http://gnosis.cx/publish/programming/charming_python_b25.html

(the URL for the IBM version seems to have gone 404).

I do know why things are as they are and how to work with them... but hey,
at least it let me coin the phrase "Incomparable abominations" which I am
still rather proud of.


On Tue, Jan 21, 2014 at 1:21 PM, Chris Angelico <rosuav at gmail.com> wrote:

> On Wed, Jan 22, 2014 at 8:11 AM, David Mertz <mertz at gnosis.cx> wrote:
> > But this is just a question of inequality versus identity and that sets
> and
> > dictionaries are, IMO, too sloppy about that.  That is, they behave
> exactly
> > as documented and as the BDFL has decreed, but I still feel uneasy about:
> >
> >   >>> a = {1, 1+0j, 2}
> >   >>> b = {1+0j, 1, 2}
> >   >>> a
> >   {(1+0j), 2}
> >   >>> b
> >   {1, 2}
> >   >>> a == b
> >   True
>
> This is because Python's made the decision that an int, a float, and a
> complex, representing the same number, should compare equal. I
> personally think they shouldn't (partly because it implies that
> they're all in some sort of tower, where the higher types can
> represent the lower types perfectly, and can perfectly represent that
> there's no further information - true of (float, complex) but not of
> (int, float), and it leads to problems with large integers), but it's
> a decision that's been made, and sets/dicts have to follow that. With
> small numbers, it just means that there's an identity-vs-value
> distinction (1 == 1.0 == 1+0j, but they're not is-identical), and sets
> have always had and will always have that issue.
>
> ChrisA
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