#10021: Empty LatticePolytope fails
------------------------+---------------------------------------------------
Reporter: vbraun | Owner: mhampton
Type: defect | Status: new
Priority: major | Milestone: sage-4.6.1
Component: geometry | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
------------------------+---------------------------------------------------
As return values for `Polyhedron.lattice_polytope()` we sometimes want to
return empty lattice polytopes. Alas, this does not work:
{{{
Lsage: LatticePolytope( matrix(ZZ,3,0) )
---------------------------------------------------------------------------
IndexError Traceback (most recent call
last)
/home/vbraun/opt/sage-4.5.3/devel/sage-main/<ipython console> in
<module>()
/home/vbraun/Sage/sage/local/lib/python2.6/site-
packages/sage/geometry/lattice_polytope.pyc in LatticePolytope(data, desc,
compute_vertices, copy_vertices, n)
264 return data
265 else:
--> 266 return LatticePolytopeClass(data, desc, compute_vertices,
copy_vertices, n)
267
268 copy_reg.constructor(LatticePolytope) # "safe for unpickling"
/home/vbraun/Sage/sage/local/lib/python2.6/site-
packages/sage/geometry/lattice_polytope.pyc in __init__(self, data, desc,
compute_vertices, copy_vertices, n)
402 if compute_vertices:
403 self._vertices = data # Temporary assignment
--> 404 self._compute_dim(compute_vertices=True)
405 else:
406 if copy_vertices:
/home/vbraun/Sage/sage/local/lib/python2.6/site-
packages/sage/geometry/lattice_polytope.pyc in _compute_dim(self,
compute_vertices)
494 else:
495 points = self._vertices.columns(copy=False)
--> 496 p0 = points[0]
497 if p0 != 0:
498 points = [point - p0 for point in points]
IndexError: list index out of range
}}}
The attached patch fixes this and adds a suitable doctest.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10021>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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