f_lshift         2023 rational.c     	    return f_to_r(f_lshift(f, n));
f_lshift         2025 rational.c     	return rb_rational_new2(f, f_lshift(ONE, INT2FIX(ln)));
f_lshift         2055 rational.c             return rb_rational_new1(f_lshift(f, n));
f_lshift         2062 rational.c             den = f_lshift(ONE, f_sub(ONE, n));