// explicit is important for g[ {1,2}] to disambiguate the mesh_point_t and the mesh_index_t
explicit mesh_point(mesh_t const& mesh, mesh_t::index_t const& index)
: index3_generator(mesh.get_dimensions(), index), m(&mesh) {}
// explicit is important for g[ {1,2}] to disambiguate the mesh_point_t and the mesh_index_t
explicit mesh_point(mesh_t const& mesh, mesh_t::index_t const& index)
: index3_generator(mesh.get_dimensions(), index), m(&mesh) {}