Closed jeanluct closed 9 years ago
Maybe the help on loop.plot is out of date? It seems that loop(2,'basepoint')
would be needed to add the basepoint.
We already disallow empty coordinates:
>> l=loop([])
Error using braidlab.loop
Loop coordinate array cannot be empty.
Hence it seems sensible to just disallow loop(2)
and loop(1,'BasePoint
)`. These have been split to return two error messages:
>> loop(2)
Error using braidlab.loop (line 206)
Need at least three punctures.
>> loop(1,'bp')
Error using braidlab.loop (line 210)
Need at least two punctures in addition to basepoint.
Also note that I fixed the help message. The relevant part of help loop.loop
now returns
L = loop(N) where N is an integer (N>2) creates a loop object L with
N punctures. The loop L is a (nonoriented) generating set for the
fundamental group of the sphere with N-1 punctures, with the Nth
puncture serving as the basepoint. This sort of object is
convenient when looking for growth of loops under braid action.
For the basepoint case, N>1
is required.
crashes Matlab. Oops.
But this might be arising from a deeper problem: shouldn't loop(2) return a loop with 3 punctures, according to the help page, since the default is to add a basepoint? Check the guide.