Documentation Decimal power 0 to the 0 is Nan (versus 0 to the 0 which is 1)

[JD-Veiga]

BPO	41205
Nosy	@tim-one, @rhettinger, @facundobatista, @mdickinson, @skrah, @srinivasreddy, @miss-islington
PRs	bpo-41205: Document Decimal power 0 to the 0 #21386 [3.9] bpo-41205: Document Decimal power 0 to the 0 (GH-21386) #21547 [3.8] bpo-41205: Document Decimal power 0 to the 0 (GH-21386) #21548

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-07-03.22:51:25.441>
labels = ['type-feature', '3.8', '3.9', '3.10', 'docs']
title = 'Documentation Decimal power 0 to the 0 is Nan (versus 0 to the 0 which is 1)'
updated_at = <Date 2020-08-15.20:48:36.169>
user = 'https://bugs.python.org/JD-Veiga'

bugs.python.org fields:

activity = <Date 2020-08-15.20:48:36.169>
actor = 'skrah'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2020-07-03.22:51:25.441>
creator = 'JD-Veiga'
dependencies = []
files = []
hgrepos = []
issue_num = 41205
keywords = ['patch']
message_count = 10.0
messages = ['372969', '372975', '372980', '372982', '372986', '373225', '373956', '373958', '373959', '375495']
nosy_count = 9.0
nosy_names = ['tim.peters', 'rhettinger', 'facundobatista', 'mark.dickinson', 'skrah', 'docs@python', 'thatiparthy', 'miss-islington', 'JD-Veiga']
pr_nums = ['21386', '21547', '21548']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'pending'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue41205'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

[JD-Veiga]

Hi,

I would like to propose a minor addition to decimal package documentation page (https://docs.python.org/3/library/decimal.html). I think that we should add a paragraph in context.power(x, y, modulo=None) stating that Decimal(0) ** Decimal(0) returns Decimal('NaN') instead of 1 --as 0 ** 0 does-- or 1.0 --in case of 0.0 ** 0.0.

Indeed, 0 ** 0 is NaN is mentioned as example of operations raising InvalidOperation exceptions.

However, I think that this is not enough to indicate the different behaviour of decimal versus int and float numbers.

Moreover, in the case of % and // operators, there are clear remarks on these differences (See: “There are some small differences between arithmetic on Decimal objects and arithmetic on integers and floats [...]” in the page).

Thank you and sorry for the inconvenience.

[tim-one]

Huh! I thought everyone in Standards World gave up by now, and agreed 0**0 should be 1.

[JD-Veiga]

Well, it is the way that it has been defined in decimal package and in the document that inspired this package (IBM's General Decimal Arithmetic Specification, The General Decimal Arithmetic Specification: http://speleotrove.com/decimal/decarith.html).