DECLARE_SCHEME_CALLBACK (rest_collision_callback, (SCM element, SCM prev_off));
DECLARE_SCHEME_CALLBACK (pure_rest_collision_callback, (SCM element, SCM, SCM, SCM prev_off));
DECLARE_SCHEME_CALLBACK (print, (SCM));
DECLARE_SCHEME_CALLBACK (rest_collision_callback, (SCM element, SCM prev_off));
DECLARE_SCHEME_CALLBACK (pure_rest_collision_callback, (SCM element, SCM, SCM, SCM prev_off));
DECLARE_SCHEME_CALLBACK (print, (SCM));