[issue23185] add inf and nan to math module

STINNER Victor added the comment: Guido van Rossum added the comment: Should inf and nan be added to cmath too? It has e and pi and isnan() and isinf()... Also complex(0, math.nan) a value that is printed as nanj and complex(nanj) parses and returns such a value, so the point could be

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: Opened issue #23229. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue23185 ___ ___ Python-bugs-list mailing

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: Should inf and nan be added to cmath too? Hmm; probably, yes. I'll open an issue. so the point could be made that there should be a constant named complex.nanj Yes, I suppose it could (along with infj, of course). I don't like it much, and I suspect it

[issue23185] add inf and nan to math module

Guido van Rossum added the comment: Should inf and nan be added to cmath too? It has e and pi and isnan() and isinf()... Also complex(0, math.nan) a value that is printed as nanj and complex(nanj) parses and returns such a value, so the point could be made that there should be a constant

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: Committed. Thanks for all the helpful review comments! -- resolution: - fixed stage: needs patch - resolved status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue23185

[issue23185] add inf and nan to math module

Roundup Robot added the comment: New changeset cf4bf577749c by Mark Dickinson in branch 'default': Issue #23185: add math.inf and math.nan constants. https://hg.python.org/cpython/rev/cf4bf577749c -- nosy: +python-dev ___ Python tracker

[issue23185] add inf and nan to math module

Changes by Ethan Furman et...@stoneleaf.us: -- nosy: +eric.smith, lemburg, rhettinger, stutzbach ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue23185 ___

[issue23185] add inf and nan to math module

STINNER Victor added the comment: 2015-01-09 8:16 GMT+01:00 Serhiy Storchaka rep...@bugs.python.org: May be make math.inf and math.nan special objects so that for all x (except inf and nan): What do you mean? Implement a subtype of float and override some methods? x math.inf x -math.inf

[issue23185] add inf and nan to math module

Serhiy Storchaka added the comment: May be make math.inf and math.nan special objects so that for all x (except inf and nan): x math.inf x -math.inf not (x math.nan) not (x math.nan) -- ___ Python tracker rep...@bugs.python.org

[issue23185] add inf and nan to math module

STINNER Victor added the comment: Except of my small suggestion on the doc (see the review), math_inf_nan4.patch looks good to me. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue23185 ___

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: I have an updated patch taking into account the most recent review comments (for which thanks!), but it's at home; I'll upload it this evening (UTC+00:00). -- ___ Python tracker rep...@bugs.python.org

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: New patch, addressing review comments. -- Added file: http://bugs.python.org/file37647/math_inf_nan4.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue23185

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: One more patch, fixing a misplaced period. -- Added file: http://bugs.python.org/file37635/math_inf_nan3.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue23185

[issue23185] add inf and nan to math module

STINNER Victor added the comment: History, perhaps? In any case, the sign of a NaN isn't useful information in the same way that the sign of an infinity is. The IEEE 754 standard explicitly refuses to attach any meaning to the sign bit of a NaN. And if we were aiming for a full and

[issue23185] add inf and nan to math module

Changes by Berker Peksag berker.pek...@gmail.com: -- components: +Library (Lib) stage: - needs patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue23185 ___

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: Sounds good to me. Do we add a math.neginf IMO no: -inf should be fine. -- nosy: +mark.dickinson ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue23185 ___

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: float(-inf) and -float(inf) have exactly the same IEEE 754 representation Indeed: there's only one negative infinity (and only one positive infinity) in IEEE 754 binary64 format. -- ___ Python tracker

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: Implementation suggestion: if possible, use the _Py_dg_stdnan and _Py_dg_infinity functions from Python/dtoa.c. These are a little safer than the Py_NAN and Py_HUGE_VAL macros, and will give results consistent with the float(inf) and float(nan)

[issue23185] add inf and nan to math module

New submission from Ethan Furman: Proposal: math.nan = float('nan') math.inf = float('inf') Guido's approval: https://mail.python.org/pipermail/python-ideas/2015-January/030775.html Followup question: Do we add a math.neginf, or somesuch, for float('-inf')? Or just use

[issue23185] add inf and nan to math module

STINNER Victor added the comment: Do we add a math.neginf, or somesuch, for float('-inf')? Or just use -math.inf? I would prefer to only add inf. It looks like float(-inf) and -float(inf) have exactly the same IEEE 754 representation (at least on my x86_64 CPU): struct.pack(d,

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: Why does Python return the same representation for positive and negative NaN? History, perhaps? In any case, the sign of a NaN isn't useful information in the same way that the sign of an infinity is. The IEEE 754 standard explicitly refuses to attach any

[issue23185] add inf and nan to math module

Serhiy Storchaka added the comment: There are several different NaNs. x = struct.unpack('d', b'\x00\x00\x00\x00\x00\x00\xf8\x7f')[0] x nan x == x False struct.pack('d', x) b'\x00\x00\x00\x00\x00\x00\xf8\x7f' x = struct.unpack('d', b'\x00\x00\x00\x00\x00\x00\xf9\x7f')[0] x nan x == x

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: but 0*inf and inf-inf return values with the same representation as float('-nan'), not float('nan') Right: that's because Intel's default NaN (i.e., the float it produces as a result of any invalid operation) has its sign bit set. --

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: By tweaking the grammar we can have math.-inf. RRGH! -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue23185 ___

[issue23185] add inf and nan to math module

Antoine Pitrou added the comment: By tweaking the grammar we can have math.-inf. -- nosy: +pitrou ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue23185 ___

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: Here's a patch. -- assignee: - mark.dickinson keywords: +patch Added file: http://bugs.python.org/file37633/math_inf_nan.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue23185

[issue23185] add inf and nan to math module

Mark Dickinson added the comment: Thanks for the review comments. Here's an updated patch taking the review comments into account (and fixing the spelling of PY_NAN, which should have been Py_NAN). -- Added file: http://bugs.python.org/file37634/math_inf_nan2.patch

[issue23185] add inf and nan to math module

STINNER Victor added the comment: Oh, NaN can be signed? struct.pack(d, float(nan)) b'\x00\x00\x00\x00\x00\x00\xf8\x7f' struct.pack(d, float(-nan)) b'\x00\x00\x00\x00\x00\x00\xf8\xff' struct.pack(d, -float(nan)) b'\x00\x00\x00\x00\x00\x00\xf8\xff' struct.pack(d, -float(-nan))