On Mon, Jun 14, 2010 at 05:33:58AM -0700, Frédéric Chapoton wrote:
> Ooops,
> This is because I did not use the root lattice.. This works :
>
> sage: A3=RootSystem(['A',3]).root_lattice()
> sage: t=A3.simple_root(1)+A3.simple_root(2)-A3.simple_root(3)
> sage: t.is_positive_root()
> False
>
> But
Ooops,
This is because I did not use the root lattice.. This works :
sage: A3=RootSystem(['A',3]).root_lattice()
sage: t=A3.simple_root(1)+A3.simple_root(2)-A3.simple_root(3)
sage: t.is_positive_root()
False
But anyway, I think the name is not correct, because it does not
return true for positive
