#29843 introduces a bug in Polyhedron().linear_transformation #30146
Description
In 9.2.beta5 applying linear transformations to a polyhedron containing a ray is broken:
sage: Polyhedron(rays=[(0,1)]).linear_transformation(identity_matrix(2))
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-185-3c5f2df4fe7c> in <module>()
----> 1 Polyhedron(rays=[(Integer(0),Integer(1))]).linear_transformation(identity_matrix(Integer(2)))
/opt/sage/sage/local/lib/python3.7/site-packages/sage/geometry/polyhedron/base.py in linear_transformation(self, linear_transf, new_base_ring)
5093
5094 sage: P = Polyhedron([(0,0),(1,1)], base_ring=ZZ)
-> 5095 sage: P.intersection(P)
5096 A 1-dimensional polyhedron in ZZ^2 defined as the convex hull of 2 vertices
5097 sage: Q = Polyhedron([(0,1),(1,0)], base_ring=ZZ)
/opt/sage/sage/local/lib/python3.7/site-packages/sage/geometry/polyhedron/base.py in __init__(self, parent, Vrep, Hrep, Vrep_minimal, Hrep_minimal, pref_rep, **kwds)
218 # TODO: find something better *but* fast
219 return hash((self.dim(),
--> 220 self.ambient_dim(),
221 self.n_Hrepresentation(),
222 self.n_Vrepresentation(),
/opt/sage/sage/local/lib/python3.7/site-packages/sage/geometry/polyhedron/backend_ppl.py in _init_from_Vrepresentation(self, vertices, rays, lines, minimize, verbose)
75 d = LCM_list([denominator(r_i) for r_i in r])
76 if d.is_one():
---> 77 gs.insert(ray(Linear_Expression(r, 0)))
78 else:
79 dr = [ d*r_i for r_i in r ]
ppl/generator.pyx in ppl.generator.Generator.ray()
ppl/generator.pyx in ppl.generator.Generator.ray()
ValueError: PPL::ray(e):
e == 0, but the origin cannot be a ray.
this used to work just fine in 9.2.beta4.
git bisect seems to blame the regression on #29843
CC: @jplab @LaisRast @kliem @mkoeppe
Component: geometry
Keywords: combinatorial polyhedron, linear transformation
Author: Jonathan Kliem
Branch/Commit: c9c7b63
Reviewer: Matthias Koeppe
Issue created by migration from https://trac.sagemath.org/ticket/30146