Bugs in the lexer and parser documentation

[Franois-RenRideau]

BPO	21972
Nosy	@loewis, @benjaminp

^{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 = <Date 2014-08-05.16:03:12.304>
created_at = <Date 2014-07-13.03:49:36.086>
labels = ['type-bug', 'docs']
title = 'Bugs in the lexer and parser documentation'
updated_at = <Date 2014-08-05.16:03:12.303>
user = 'https://bugs.python.org/Franois-RenRideau'

bugs.python.org fields:

activity = <Date 2014-08-05.16:03:12.303>
actor = 'loewis'
assignee = 'docs@python'
closed = True
closed_date = <Date 2014-08-05.16:03:12.304>
closer = 'loewis'
components = ['Documentation']
creation = <Date 2014-07-13.03:49:36.086>
creator = 'Fran\xc3\xa7ois-Ren\xc3\xa9.Rideau'
dependencies = []
files = []
hgrepos = []
issue_num = 21972
keywords = []
message_count = 7.0
messages = ['222906', '222907', '222936', '224844', '224846', '224847', '224850']
nosy_count = 5.0
nosy_names = ['loewis', 'benjamin.peterson', 'docs@python', 'python-dev', 'Fran\xc3\xa7ois-Ren\xc3\xa9.Rideau']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue21972'
versions = ['Python 3.5']

[Franois-RenRideau]

The lexer documentation says that the u prefix works on strings since 3.3, but doesn't explain what or how, which is all the more problematic since it explicitly mentions difference from the behavior documented in Python 2.

It also doesn't specify the ELLIPSIS token or the <> future token mentioned in the grammar (that should probably be removed, for PEP-401 is a joke — unless that's intentional, in which case a smiley might be useful).

https://docs.python.org/3.5/reference/lexical_analysis.html

[loewis]

I don't understand. It says "it is possible again to prefix unicode strings with a u prefix" which seems to include both what ("prefix unicode strings") and how ("with a u prefix").

Can you propose specific wording that you want to see included?

[Franois-RenRideau]

Actually, my reading was buggy, and the "u" part is well-documented enough. Apologies for this part of the bug report.

The lexer documentation is still missing the ellipsis, though

Other bug I found in the lexer documentation: missing @=

And the parser documentation of <> is probably a bug.

[loewis]

The ellipsis is also mentioned: "A sequence of three periods has a special meaning as an ellipsis literal."

[loewis]

The PEP-401 joke actually works:

>>> from __future__ import barry_as_FLUFL
>>> 3<>4
True

I'll add a smiley

[python-dev]

New changeset 57740d19f5c2 by Martin v. Löwis in branch 'default':
Issue bpo-21972: Make it clear that the PEP-401 future import works,
http://hg.python.org/cpython/rev/57740d19f5c2

[loewis]

I've moved the @ operator into bpo-22142. With that, it seems to me that all aspects of this report are resolved.

François-René, for the future, please submit an individual bug report for each independent issue; this makes it easier tracking what has and hasn't been resolved.