Messages (9) msg58037 - (view) Author: Christian Heimes (christian.heimes) * Date: 2007-12-01 01:22

Currently Python has no information about the maximum and minimum value
of a float. The patch adds a dict with all important information to sys:
>>> pprint.pprint(sys.maxfloat)
{'dig': 15,
 'epsilon': 2.2204460492503131e-16,
 'mant_dig': 53,
 'max': 1.7976931348623157e+308,
 'max_10_exp': 308,
 'max_exp': 1024,
 'min': 2.2250738585072014e-308,
 'min_10_exp': -307,
 'min_exp': -1021,
 'radix': 2,
 'rounds': 1}
The patch compiles on Linux and Windows.

msg58038 - (view) Author: Guido van Rossum (gvanrossum) * Date: 2007-12-01 01:25

I'd suggest giving it a different name, maybe float_info.  sys.maxfloat
suggests the value is a float, like sys.maxint and sys.maxunicode.

msg58041 - (view) Author: Christian Heimes (christian.heimes) * Date: 2007-12-01 11:24

Applied in r59254.
I've moved the code to floatobject.c/h and added PyFloat_GetMax() and
PyFloat_GetMin(), too. The intobject.c file has a similar function.

msg58051 - (view) Author: Mark Dickinson (mark.dickinson) * Date: 2007-12-01 15:55

A (probably stupid) question:  what's supposed to happen on platforms that
don't define things like DBL_MAX_10_EXP, which isn't part of ANSI C89?  Or
are there no such platforms?

msg58053 - (view) Author: Christian Heimes (christian.heimes) * Date: 2007-12-01 16:03

I've checked all major platforms before committing the patch. They all
have a float.h with the information available. Do you know of a platform
where this information isn't available? I could add a lot of #ifdef but
I don't feel like bloating the code unless it is necessary.

msg58054 - (view) Author: Mark Dickinson (mark.dickinson) * Date: 2007-12-01 16:17

No, I don't know of any platforms that don't define these constants.

msg58055 - (view) Author: Mark Dickinson (mark.dickinson) * Date: 2007-12-01 16:37

And it looks as though DBL_MAX_10_EXP *is* part of ANSI C anyway...  I
shouldn't have assumed that just because it's not in Kernighan and Ritchie
(2nd edition) it doesn't exist...  Apologies.

msg58062 - (view) Author: Christian Heimes (christian.heimes) * Date: 2007-12-01 18:06

Thanks for checking it out for me! Do you have a reliable online source
for the ANSI C89 standard? I'm usually using the GNU C Library docs but
the site doesn't list what's available in C89.

msg58075 - (view) Author: Mark Dickinson (mark.dickinson) * Date: 2007-12-02 01:17

The site that persuaded me about DBL_MAX_10_EXP was
http://www.schweikhardt.net/identifiers.html
Googling 'C89 draft' also turns up some potentially useful stuff.

History Date User Action Args 2022-04-11 14:56:28adminsetgithub: 45875 2008-01-06 22:29:44adminsetkeywords: - py3k
versions: Python 2.6, Python 3.0 2007-12-02 01:17:16mark.dickinsonsetmessages: + msg58075 2007-12-01 18:06:09christian.heimessetmessages: + msg58062 2007-12-01 16:37:12mark.dickinsonsetmessages: + msg58055 2007-12-01 16:17:47mark.dickinsonsetmessages: + msg58054 2007-12-01 16:03:26christian.heimessetmessages: + msg58053 2007-12-01 15:55:43mark.dickinsonsetnosy: + mark.dickinson
messages: + msg58051 2007-12-01 11:24:11christian.heimessetstatus: open -> closed
resolution: fixed
messages: + msg58041 2007-12-01 01:25:17gvanrossumsetnosy: + gvanrossum
messages: + msg58038 2007-12-01 01:22:16christian.heimescreate