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Re: NaN comparisons - Call For Anecdotes

From Marko Rauhamaa <marko@pacujo.net>
Newsgroups comp.lang.python
Subject Re: NaN comparisons - Call For Anecdotes
Date 2014-07-17 22:10 +0300
Organization A noiseless patient Spider
Message-ID <877g3b244v.fsf@elektro.pacujo.net> (permalink)
References (4 earlier) <mailman.11716.1404946997.18130.python-list@python.org> <osx38e010kj.fsf@gmail.com> <mailman.11929.1405611387.18130.python-list@python.org> <osxwqbbzuqc.fsf@gmail.com> <mailman.11950.1405623342.18130.python-list@python.org>

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Chris Angelico <rosuav@gmail.com>:

> numerical calculations might overflow to +inf or -inf, and then
> further calculations can result in a nan, etc, etc. Those are the
> sorts of examples that you'd find among SciPy users and such.

There is some inconsistency.

Mathematically, there are undefined operations, for a good reason.
That's because the limits are not unambiguous and that's why 0/0, 0**0,
1/0 and inf-inf are undefined.

Why 0/0 results in an exception but inf-inf = nan, I don't see a
justification.


Marko

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Re: NaN comparisons - Call For Anecdotes "Anders J. Munch" <2014@jmunch.dk> - 2014-07-10 01:03 +0200
  Re: NaN comparisons - Call For Anecdotes Johann Hibschman <jhibschman@gmail.com> - 2014-07-17 11:12 -0400
    Re: NaN comparisons - Call For Anecdotes Chris Angelico <rosuav@gmail.com> - 2014-07-18 01:36 +1000
      Re: NaN comparisons - Call For Anecdotes Johann Hibschman <jhibschman@gmail.com> - 2014-07-17 14:49 -0400
        Re: NaN comparisons - Call For Anecdotes Chris Angelico <rosuav@gmail.com> - 2014-07-18 04:55 +1000
          Re: NaN comparisons - Call For Anecdotes Marko Rauhamaa <marko@pacujo.net> - 2014-07-17 22:10 +0300
            Re: NaN comparisons - Call For Anecdotes Ian Kelly <ian.g.kelly@gmail.com> - 2014-07-17 14:39 -0600
              Re: NaN comparisons - Call For Anecdotes Marko Rauhamaa <marko@pacujo.net> - 2014-07-18 00:08 +0300
                Re: NaN comparisons - Call For Anecdotes Ian Kelly <ian.g.kelly@gmail.com> - 2014-07-17 17:00 -0600
                Re: NaN comparisons - Call For Anecdotes Ian Kelly <ian.g.kelly@gmail.com> - 2014-07-17 17:07 -0600
        Re: NaN comparisons - Call For Anecdotes Chris Angelico <rosuav@gmail.com> - 2014-07-18 04:59 +1000
      Re: NaN comparisons - Call For Anecdotes Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-07-18 17:57 +0000
        Re: NaN comparisons - Call For Anecdotes Chris Angelico <rosuav@gmail.com> - 2014-07-19 05:49 +1000

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