ElementLineP0

[gdmcbain]

We have ElementTriP0 , ElementQuad0 #266, ElementTetP0, but not ElementLineP0 (or the hexahedron).

[gdmcbain]

An anomaly:

• these are O. K.:
  • FacetBasis(MeshTri(), ElementTriP0())
  • FacetBasis(MeshTet(), ElementTetP0())
  • FacetBasis(MeshLine(), ElementLineP0()), from ElementLineP0 #509 at 25a636a
• but this isn't
  • FacetBasis(MeshQuad(), ElementQuad0())

raising ValueError: operands could not be broadcast together with remapped shapes [original->remapped]: (4,) and requested shape (4,2)

[kinnala]

Seems there is actually a bug in element_quad0.py. np.ones(X.shape[1]) should be replaced with, e.g., np.zeros_like(X[0]) + 1. Maybe np.ones(X.shape[1:]) would also work. The thing is that X has different shape in InteriorBasis and FacetBasis.