numeric.c:1523
static VALUE
fix_lt(x, y)
    VALUE x, y;
{
    if (FIXNUM_P(y)) {
	long a = FIX2LONG(x), b = FIX2LONG(y);

	if (a < b) return Qtrue;
	return Qfalse;
    }
    else {
	return rb_num_coerce_relop(x, y);
    }
}
