On 11 Jul 2021, at 05:33, John Cowan <xxxxxx@ccil.org> wrote:

> 2) ordered (O) / hash (H)

Ordered, sorted, or hash.

Ordered: Remembers what order you put things into it (list, vector, deque, etc.)
Sorted: Keeps contents in an order determined by a comparison predicate (most kinds of trees)
Hash: No guarantees about what order things come out of the collection (typical hash table implementation)

Daphne