public int lower(T v) {
        return Boundary.LOWER.apply(find(v));
    }
@Test
    public void testLower() {
        assertEquals(-1, l.lower("A"));
        assertEquals(-1, l.lower("B"));
        assertEquals(0, l.lower("C"));
        assertEquals(0, l.lower("D"));
        assertEquals(1, l.lower("E"));
        assertEquals(1, l.lower("F"));
        assertEquals(2, l.lower("G"));
    }