Reactive programming facilities

[leonoel]

Rationale : modeling DAG topologies.

Guidelines :

• glitch-free. If C depends on A and B, and B depends on A, C must consider event A and B's reaction to event A as simultaneous, and react only once.
• dynamic topology. A new node can be spawned in reaction to an event in another node. If node B subscribes to node A in reaction to an event in A, the event and the subscription must be considered simultaneous so B must be notified of the event.
• support for both discrete and continuous nodes (events and behavior, in original FRP). A discrete node consumes its flow eagerly and propagates backpressure from its subscribers. A continuous node consumes its flow lazily, the current value is sampled when the first subscriber asks for it and the value is then cached for next subscribers until invalidated.
• strict supervision. At any time it must be possible to cancel an entire graph. If a node fails, the graph must be cancelled. A graph is terminated when all of its nodes are terminated.

API design :

• reactor takes an initializer thunk and returns a task. Running the task evaluates the thunk within a fresh reactor. A node can be spawned only in the dynamic context of a reactor (in the initializer, or in reaction to an event of another node).
• stream! and signal! take a flow, spawn a node running this flow (resp. discrete and continuous) and return a flow subscribing to this node.

[leonoel]

First release in version b.14

[jjttjj]

Any chance you could provide a small example of this?

[leonoel]

Have a look at this gist

[jjttjj]

Thanks!