+--------+----------------------------------+
| bitmap | 00000000000000010000001000000000 |
+--------+----------------------------------+
|        | +-+-+                            |
| array  | | | |                            |
|        | +++++                            |
+--------+--+-+-----------------------------+
            | |
            | +-----------+
            |             |
            v             v
       /----------\  /----------\
       | bar → 17 |  | foo → 42 |
       \----------/  \----------/