[issue39310] Add math.ulp(x): unit in the last place

[STINNER Victor]

STINNER Victor <vstinner at python.org> added the comment:

See also math.isclose() and its PEP 485 which mentions ULP (Unit in the Last Place)... in the "Inappropriate uses" section :-)

* https://docs.python.org/dev/library/math.html#math.isclose
* https://www.python.org/dev/peps/pep-0485/#inappropriate-uses

Extract of an old python-ideas discussion on adding nextafter():

"It's also a little weird to jump from nextafter to isclose, since AFAIK
they have pretty much non-overlapping use cases..."

https://mail.python.org/pipermail/python-ideas/2017-February/044832.html

Other links:

* https://en.wikipedia.org/wiki/Unit_in_the_last_place
* https://en.wikipedia.org/wiki/Machine_epsilon
* https://en.wikipedia.org/wiki/IEEE_754

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