prec.c:70
void
Init_Precision()
{
    rb_mPrecision = rb_define_module("Precision");
    rb_define_singleton_method(rb_mPrecision, "included", prec_included, 1);
    rb_define_method(rb_mPrecision, "prec", prec_prec, 1);
    rb_define_method(rb_mPrecision, "prec_i", prec_prec_i, 0);
    rb_define_method(rb_mPrecision, "prec_f", prec_prec_f, 0);

    prc_pr = rb_intern("prec");
    prc_if = rb_intern("induced_from");
}
