#15384: Improvements to root systems
-------------------------------------+-------------------------------------
Reporter: tscrim | Owner: sage-combinat
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.3
Component: combinatorics | Resolution:
Keywords: root systems, | Merged in:
days54 | Reviewers: Dan Bump
Authors: Travis Scrimshaw | Work issues:
Report Upstream: N/A | Commit:
Branch: | 66f5674bf4281706f71f01202091ed02e1ee8bcc
public/combinat/root_systems/improvements-15384| Stopgaps:
Dependencies: |
-------------------------------------+-------------------------------------
Comment (by bump):
What about this?
{{{
sage: RootSystem(['D',4,2]).root_lattice().positive_roots()
---------------------------------------------------------------------------
AttributeError Traceback (most recent call
last)
<ipython-input-11-ea364fc7aada> in <module>()
----> 1
RootSystem(['D',Integer(4),Integer(2)]).root_lattice().positive_roots()
-snip -
AttributeError: 'NoneType' object has no attribute 'dual'
}}}
BTW Sage reports this root system as Root lattice of the Root system of
type ['C', 3, 1]^*
If I have my facts straight Macdonald introduced a classification of
affine root systems in his
paper "Affine root systems and the Dedekind eta function" Inventiones 1972
but
Kac didn't follow Macdonald. He introduced his own classification. So we
are
entering root systems in Kac' notation and they are getting converted
automatically
to Macdonald's notation. Of course that policy was not introduced by this
patch but
I mention that I've personally found it a little confusing.
--
Ticket URL: <http://trac.sagemath.org/ticket/15384#comment:28>
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