The type of typed streams.

The type for stream sessions.

session init creates a fresh session, whose initial value is init.

publish s v publishes v in the session s.

create pp session is a fresh file stream. Readers of the stream will first get an initial line, printed with pp, corresponding to the current session's value. Everytime the session's state is changing, a new line -- formatted with pp -- is broadcasted to all the current readers of the stream.