#19159: Check if a word is a Christoffel word.
-------------------------------------+-------------------------------------
Reporter: mlapointe | Owner: mlapointe
Type: enhancement | Status: needs_work
Priority: minor | Milestone: sage-6.9
Component: combinatorics | Resolution:
Keywords: words, | Merged in:
Christoffel, days69 | Reviewers:
Authors: Mélodie Lapointe | Work issues:
Report Upstream: N/A | Commit:
Branch: | dceb8c447b2f6ac617cb7c3328c83b47458ad2c8
u/mlapointe/check_if_a_word_is_a_christoffel_word_| Stopgaps:
Dependencies: |
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Changes (by nadialafreniere):
* status: needs_review => needs_work
Comment:
{{{#!diff
#A Christoffel word is a non-empty word over a binary alphabet
+ if len(self) < 0 or len(self.letters()) > 2 or
self.is_palindrome():
+ return False
+ elif self.is_symmetric() and self[1:len(self)-1].is_palindrome():
+ return True
+ else:
+ return False
}}}
A comment should always start with a space after '#'. As well,
`self[1:len(self)-1]` should be transformed in `self[1:len(self) - 1]`.
For more info on Python and Sage conventions, see
http://doc.sagemath.org/html/en/developer/coding_basics.html#python-code-
style
I'm also wondering about the first condition: When the length of a word
can be strictly shorter than 0?
Also, a single letter is a Christoffel word, according to the reference
you give (Berstel et al.) Right now, it returns false because it is a
palindrome. You should add a test for it.
--
Ticket URL: <http://trac.sagemath.org/ticket/19159#comment:6>
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