[Octave-bug-tracker] [bug #51283] function min/max inconsistent handling of -0

[Oliver Heimlich]

Follow-up Comment #4, bug #51283 (project octave):

The floating point values -0 and 0 must be considered equal and the max
function may return either of them, see the maxNum function in IEEE Std
754-2008.

Also, the standard for floating point arithmetic says in chapter 11
(reproducible floating-point results) that users should write programs in such
a way that they do not depend “on the sign of a zero result … for …
maxNum (x, y) … when x and y are equal”.

Strictly speaking, Octave behaves well.  However, I'd find it reasonable if
Octave could return bit-equal results for the expressions max (x, y) and max
([x, y]).  And it should be irrelevant whether x and y are scalars or vectors
for choosing the first or second argument in cases where both are
(semantically) equal.


Regarding the interval package: That should be fixed in the sine function. 
There already is a “l(l == 0) = -0;” for fixing the lower boundary.  The
upper boundary can equally be fixed with “u(u == 0) = +0;”.  I have added
these expressions in all cases where they could be needed, but obviously
forgot it in sine.

For intervals, the lower boundary may not be stored as +0 internally.  And the
upper boundary may not be stored as -0 internally.  This is enforced by the
constructor.  Many arithmetic operations use a shortcut and don't call the
constructor, thus have to ensure this condition in the function file.

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