···
A sink has the signature: `signalT('a) => unit`
A source thus has the signature: `sink => unit`, or `(signalT('a) => unit) => unit`
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Effectively a sink is a callback receiving signals as its first argument.
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- Start(talkback) will be carrying a talkback using which the sink can attempt
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to pull values (Pull) or request the source to end its stream (End)
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- Push(payload) carries a value that the source sends to the sink.
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This can happen at any time, since a source can be both pullable or
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- End signifies the end of the source stream, be it because of a talkback (End)
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or because the source is exhausted.
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In detail, a talkback is simply a callback that receives a talkback signal as
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its first argument. It's thus typically anonymously created by the source.
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A source is a factory that accepts a sink. Calling a source with a sink will
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instantiate and initiate the source's stream, after which the source sends the sink
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a talkback (Start(talkback)). This is called the "handshake".
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Typically an operator factory won't call the source with a sink it receives
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immediately—because this would cause the operator to simply be a noop—but instead
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it will create an intermediate sink with the same signature to perform its own
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At that point the operator can for instance intercept the talkback for its own
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purposes, or call the actual sink as it sees fit.
kitten.sh