DECLARE_SCHEME_CALLBACK (get_touching_point, (SCM, SCM, SCM));
DECLARE_SCHEME_CALLBACK (get_distance, (SCM, SCM, SCM));
DECLARE_SCHEME_CALLBACK (get_max_height, (SCM));
DECLARE_SCHEME_CALLBACK (get_max_height_position, (SCM));
DECLARE_SCHEME_CALLBACK (get_height, (SCM, SCM));
DECLARE_SCHEME_CALLBACK (get_touching_point, (SCM, SCM, SCM));
DECLARE_SCHEME_CALLBACK (get_distance, (SCM, SCM, SCM));
DECLARE_SCHEME_CALLBACK (get_max_height, (SCM));
DECLARE_SCHEME_CALLBACK (get_max_height_position, (SCM));
DECLARE_SCHEME_CALLBACK (get_height, (SCM, SCM));