not_null_default& operator= (T const& t) { ptr = t; ensure_invariant (); return *this; }
Plane::Plane(const Vector3d& normal, const Vector3d& x) : m_normal(normal), m_d(normal.dot(x)) { ensure_invariant(); }
not_null_default (T t) : ptr(t) { ensure_invariant(); }
//#################### CONSTRUCTORS #################### Plane::Plane(const Vector3d& normal, double d) : m_normal(normal), m_d(d) { ensure_invariant(); }