DECLARE_SCHEME_CALLBACK (print, (SCM));
DECLARE_SCHEME_CALLBACK (set_spacing_rods, (SCM));
DECLARE_SCHEME_CALLBACK (calc_direction, (SCM));
DECLARE_SCHEME_CALLBACK (print, (SCM));
DECLARE_SCHEME_CALLBACK (set_spacing_rods, (SCM));
DECLARE_SCHEME_CALLBACK (calc_direction, (SCM));