Matcher is a tool to find out what game should be played next.
There are two types of matchers: simple and continuous.
Simple matchers have fixed input set, and they create a fixed number of games.
For example RoundRobin matcher always generates (0..n).sum() games from n
participants.
Continuous matchers create an infinite stream games. They may also have dynamic input set, that allows adding (and removing) participants. Continuous matcher can also accept feedback, e.g. score or result of a match, to select future pairs.