I have taken a look at the code, and I think I have identified the
bug. I'm not sure this is the most appropriate place to suggest a
modification; if not, I hope someone can forward this to the right
address, or at least tell me where to post it.
Here are some tests showing the issue:
sage: w=Word([0,0,1,0,2,1]); w
word: 001021
sage: w.conjugate(-1) #a conjugate is just a cyclic shift
word: 100102
sage: w.conjugate(5) #cyclic shifts are defined modulo the length
word: 100102
#conjugate_position correctly shows here how much you need to shift w
to get its 0th conjugate (itself)
sage: w.conjugate(0).conjugate_position(w)
0
sage: w.conjugate(1).conjugate_position(w)
1
# in general, for primitive words (i.e., non-powers) such as w, the
result of
# w.conjugate(n).conjugate_position(w)
# should always equal n % w.length():
sage: w.conjugate(-2).conjugate_position(w)
4
sage: w.conjugate(-1).conjugate_position(w) #so here the output
should be 5, but...
sage: w.conjugate(-1).conjugate_position(w) is None #oops!
True
sage: v=Word('abacabac'); v #the square of 'abac', a non-primitive
word
word: abacabac
#the following computation is right; the bug only appears when the
expected answer is length-1
#so non-primitive words always work fine.
sage: v.conjugate(-1).conjugate_position(v)
3
________
Here is the current version of the code:
def conjugate_position(self, other):
r"""
Returns the position where self is conjugate with other.
Returns None if there is no such position.
EXAMPLES::
sage: Word('12113').conjugate_position(Word('31211'))
1
sage: Word('12131').conjugate_position(Word('12113')) is None
True
sage: Word().conjugate_position(Word('123')) is None
True
"""
if self.length() != other.length():
return None
if self == other:
return 0
for l in xrange(1, other.length() - 1):
other = other.conjugate(1)
if self == other:
return l
return None
I believe that in order to fix this bug, it is sufficient to
substitute line -5, i.e.,
for l in xrange(1, other.length() - 1):
with the following
for l in xrange(1, other.length()):
I hope I have made myself clear.
Thanks again, bye
Alessandro
On 21 Mar, 09:35, "Nicolas M. Thiery" <nicolas.thi...@u-psud.fr>
wrote:
> Hi Alessandro,
>
> On Sun, Mar 20, 2011 at 05:48:22PM -0700, Alessandro De Luca wrote:
> > I am writing because the conjugate_position method (for finite words)
> > is not working the way I expected. I believe that the output for
>
> > w.conjugate(-1).conjugate_position(w)
>
> > should equal w.length()-1 for all words w on at least two letters.
> > However, I seem to get no answer, all the time (just as if the two
> > words were not conjugate). All other positions, apart from -1, seem to
> > work just fine.
> > I'm running the latest Sage version, 4.6.2.
>
> I don't know what the right thing should be here. But please include
> examples with the obtained output and the output you'd expect:
>
> sage: w = ...
> sage.conjugate(-1).conjugate_position(w)
> ...
>
> Whatever is the conclusion of the discussion, those should be added to
> the documentation with an explanation; so this is not wasted time, and
> it makes things concrete.
>
> Thanks!
> Nicolas
> --
> Nicolas M. Thi�ry "Isil" <nthi...@users.sf.net>http://Nicolas.Thiery.name/
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