On Wednesday, 2 November 2016 at 13:45:41 UTC, Nordlöw wrote:
Typically set- and map-like containers with O(1) key membership checking.
A typical use case is intersection of the two sets `x` and `y`.When `x` and `y` both support O(1)-`contains(e)` the preferred algorithm is to interate over all elements in the shorter (smallest .length) of `x` and `y` (called `s`), and return only those elements of type E in `s` than can be looked up in `l` via `l.contains(E)`.