# Error intersecting polyhedra I have a dictionary of polyhedra which I want to consider various intersections and unions of. For now, my dictionary has four polyhedra in it. When running the following for loop:

v={} # contains coordinates of the tetrahedron, centered at (0,0,0)
v = vector([1,0,-1/sqrt(2)])
v = vector([-1,0,-1/sqrt(2)])
v = vector([0,1,1/sqrt(2)])
v = vector([0,-1,1/sqrt(2)])

V = {1,2,3,4}

b={} # will contain coordinates of vertices of the subdivision of the tetrahedron

for X in powerset(V):
q = len(X)
if q > 0:
b[tuple(X)] = (1/q)*sum([v[i] for i in X])

poly_int = Polyhedron([b[key] for key in b.keys()]) # this is a tetrahedron containing
# all of my polyhedra
for i in [1,2,3,4]:
poly_int = poly[i] & poly_int


I get a very nasty error:

AttributeError: 'Polyhedra_RDF_cdd_with_category.element_class'
object has no attribute '_Vrepresentation'


(The traceback for the error is quite long. I can include it if needed.)

Manually computing

poly & poly & poly & poly


gives the same error. HOWEVER, if instead I compute

(poly & poly) & (poly & poly)


I get no errors. While this is a fine workaround for this particular case, I'm scripting these intersections and need some way to actually compute these intersections automatically. Using something like

poly.intersection(poly) # etc.


doesn't help either. Any thoughts?

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If you could edit your question to include the definition of b that would probably help; I'm trying some basic polyhedra and just getting the empty polyhedron even with multiple &s, and the diagnosis you give indicates it's probably a very specific edge case that is going wrong. (Also note that intersection *should* (?) be the same as &, since this particular binary operator turns into __and__, I believe.)
Sorry, one more question - what is poly? I thought maybe v is poly, but that doesn't make sense.