#12462: max((5,NaN)) != max((NaN,5))
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Reporter: schilly | Owner: burcin
Type: defect | Status: closed
Priority: major | Milestone: sage-5.0
Component: symbolics | Resolution: invalid
Keywords: | Work_issues:
Upstream: N/A | Reviewer:
Author: | Merged:
Dependencies: |
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Changes (by was):
* status: new => closed
* resolution: => invalid
Comment:
I think this should be closed as invalid. In pure Python (nothing to do
with sage), we have:
{{{
$ python
Python 2.7.1 (r271:86832, Jun 16 2011, 16:59:05)
[GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)] on
darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> nan = float('nan')
>>> max(5.0, nan)
5.0
>>> max(nan, 5.0)
nan
>>> 5.0 > nan
False
>>> 5.0 < nan
False
}}}
This is a consequence of how Python's max is defined, and how IEEE defined
comparison with nan. Read about that here:
http://stackoverflow.com/questions/1565164/what-is-the-rationale-for-all-
comparisons-returning-false-for-ieee754-nan-values
See also http://stackoverflow.com/questions/4237914/python-max-min-
builtin-functions-depend-on-parameter-order for a discussion if
*precisely* this exact issue in Python.
Again, I say close this as invalid. If anybody does anything to change
Sage here, they will just make things incompatible with Python, which is a
bad, bad idea. Python has already made this design choice, and we have
to live with it.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12462#comment:2>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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