Merges a list of Pollables into a single Pollable.
Head-biased: when there is an element available from multiple upstreams, favors the upstream closest to the
head of the input list.
Merges a list of Pollables into a single Pollable.
Head-biased: when there is an element available from multiple upstreams, favors the upstream closest to the
head of the input list.
Splits a stream of "A or B" to a stream of A and a stream of B.
Splits a stream of "A or B" to a stream of A and a stream of B.
Polls the upstream only after ''both'' downstreams poll.
When either of the downstreams closes, the other downstream and the upstream are closed as well.