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(.module:
[lux #*
[control
[functor (#+ Functor)]
[apply (#+ Apply)]
["." monad (#+ do Monad)]]
["." io (#+ IO io)]
[data
[collection
[list ("list/." Monoid<List>)]]]
[type (#+ :share)
abstract]]
[//
["." atom (#+ Atom atom)]
["." promise (#+ Promise)]])
(abstract: #export (Channel a)
{#.doc "An asynchronous channel to distribute values."}
(Atom (List (-> a (IO Any))))
(def: #export (channel _)
(All [a] (-> Any (Channel a)))
(:abstraction (atom (list))))
(def: #export (listen listener channel)
(All [a] (-> (-> a (IO Any)) (Channel a) (IO Any)))
## TODO: Simplify when possible.
(do io.Monad<IO>
[_ (atom.update (|>> (#.Cons listener))
(:representation channel))]
(wrap [])))
(def: #export (publish channel value)
{#.doc "Publish to a channel."}
(All [a] (-> (Channel a) a (IO Any)))
(do io.Monad<IO>
[listeners (atom.read (:representation channel))]
(monad.map @ (function (_ listener) (listener value)) listeners)))
)
(def: #export (filter predicate input)
(All [a] (-> (-> a Bit) (Channel a) (Channel a)))
(let [output (channel [])]
(exec (io.run (listen (function (_ value)
(if (predicate value)
(publish output value)
(io [])))
input))
output)))
(def: #export (pipe output input)
{#.doc "Copy/pipe the contents of a channel on to another."}
(All [a] (-> (Channel a) (Channel a) (IO Any)))
(listen (publish output)
input))
(def: #export (merge inputs)
{#.doc "Fuse all the elements in a list of channels by piping them onto a new output channel."}
(All [a] (-> (List (Channel a)) (IO (Channel a))))
(let [output (channel [])]
(do io.Monad<IO>
[_ (monad.map @ (pipe output) inputs)]
(wrap output))))
(def: #export (from-promise promise)
(All [a] (-> (Promise a) (Channel a)))
(let [output (channel [])]
(exec (promise.await (publish output) promise)
output)))
(def: #export (poll time action)
(All [a] (-> Nat (IO a) (Channel a)))
(let [output (channel [])]
(exec (io.run
(loop [_ []]
(do io.Monad<IO>
[value action
_ (publish output value)]
(wrap (promise.await recur (promise.wait time))))))
output)))
(def: #export (periodic time)
(-> Nat (Channel Any))
(let [output (channel [])]
(exec (io.run
(loop [_ []]
(do io.Monad<IO>
[_ (publish output [])]
(wrap (promise.await recur (promise.wait time))))))
output)))
(def: #export (iterate f init)
(All [a] (-> (-> a (Promise a)) a (Channel a)))
(let [output (channel [])]
(exec (io.run
(loop [zero init]
(do io.Monad<IO>
[_ (publish output zero)]
(wrap (promise.await recur (f zero))))))
output)))
(structure: #export _ (Functor Channel)
(def: (map f input)
(let [output (channel [])]
(exec (io.run (listen (|>> f (publish output))
input))
output))))
(structure: #export _ (Apply Channel)
(def: functor Functor<Channel>)
(def: (apply ff fa)
(let [output (channel [])]
(exec (io.run (listen (function (_ f)
(listen (|>> f (publish output))
fa))
ff))
output))))
(structure: #export _ (Monad Channel)
(def: functor Functor<Channel>)
(def: (wrap a)
(let [output (channel [])]
(exec (io.run (publish output a))
output)))
(def: (join mma)
(let [output (channel [])]
(exec (io.run (listen (listen (publish output))
mma))
output))))
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