Class hpp::constraints::AffineFunction: should we handle specifically this function is the solvers ?
Class hpp::constraints::ConstantFunction: should we handle specifically this function is the solvers ?
Class hpp::constraints::Identity: should we handle specifically this function is the solvers ?
Member hpp::constraints::linePlaneIntersection (const vector3_t &A, const vector3_t &u, const vector3_t &P, const vector3_t &n): make this function robust to orthogonal inputs.