DECLARE_SCHEME_CALLBACK (calc_length, (SCM));
DECLARE_SCHEME_CALLBACK (pure_calc_length, (SCM, SCM, SCM));
DECLARE_SCHEME_CALLBACK (calc_stem_begin_position, (SCM));
DECLARE_SCHEME_CALLBACK (calc_length, (SCM));
DECLARE_SCHEME_CALLBACK (pure_calc_length, (SCM, SCM, SCM));
DECLARE_SCHEME_CALLBACK (calc_stem_begin_position, (SCM));