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|
(;module:
lux
(lux (control ["F" functor]
["A" applicative]
["M" monad #+ do Monad]
[eq #+ Eq]
["p" parser])
[io #- run]
(data (coll [list "L/" Monoid<List>])
text/format)
[macro]
(macro ["s" syntax #+ syntax: Syntax]))
(.. ["&" promise]))
## [Types]
(type: #export (Channel a)
{#;doc "An asynchronous channel of values which may be closed.
Reading from a channel does not remove the read piece of data, as it can still be accessed if you have an earlier node of the channel."}
(&;Promise (Maybe [a (Channel a)])))
## [Syntax]
(syntax: #export (channel [type s;any])
{#;doc (doc "Makes an uninitialized Channel (in this case, of Nat)."
(channel Nat))}
(wrap (list (` (: (Channel (~ type))
(&;promise' #;None))))))
## [Values]
(def: #export (filter p xs)
(All [a] (-> (-> a Bool) (Channel a) (Channel a)))
(do &;Monad<Promise>
[?x+xs xs]
(case ?x+xs
#;None (wrap #;None)
(#;Some [x xs']) (if (p x)
(wrap (#;Some [x (filter p xs')]))
(filter p xs')))))
(def: #export (write value target)
{#;doc "Write to a channel, so long as it's still open."}
(All [a] (-> a (Channel a) (IO (Maybe (Channel a)))))
(case (&;poll target)
(^template [<case> <channel-to-write>]
<case>
(do Monad<IO>
[#let [new-tail (channel ($ +0))]
done? (&;resolve (#;Some [value new-tail]) <channel-to-write>)]
(if done?
(wrap (#;Some new-tail))
(write value <channel-to-write>))))
([#;None target]
[(#;Some (#;Some [_ target'])) target'])
_
(:: Monad<IO> wrap #;None)
))
(def: #export (close target)
(All [a] (-> (Channel a) (IO Bool)))
(case (&;poll target)
(^template [<case> <channel-to-write>]
<case>
(do Monad<IO>
[done? (&;resolve #;None <channel-to-write>)]
(if done?
(wrap true)
(close <channel-to-write>))))
([#;None target]
[(#;Some (#;Some [_ target'])) target'])
_
(:: Monad<IO> wrap false)
))
(def: (pipe' input output)
(All [a] (-> (Channel a) (Channel a) (&;Promise Unit)))
(do &;Monad<Promise>
[?x+xs input]
(case ?x+xs
#;None (wrap [])
(#;Some [x input']) (case (io;run (write x output))
#;None
(wrap [])
(#;Some output')
(pipe' input' output')))))
(def: #export (pipe input output)
{#;doc "Copy/pipe the contents of a channel on to another."}
(All [a] (-> (Channel a) (Channel a) (&;Promise Unit)))
(do &;Monad<Promise>
[_ (pipe' input output)]
(exec (io;run (close output))
(wrap []))))
(def: #export (merge xss)
{#;doc "Fuse all the elements in a list of channels by piping them onto a new output channel."}
(All [a] (-> (List (Channel a)) (Channel a)))
(let [output (channel ($ +0))]
(exec (do &;Monad<Promise>
[_ (M;map @ (function [input] (pipe' input output)) xss)]
(exec (io;run (close output))
(wrap [])))
output)))
(def: #export (fold f init xs)
{#;doc "Asynchronous fold over channels."}
(All [a b] (-> (-> b a (&;Promise a)) a (Channel b) (&;Promise a)))
(do &;Monad<Promise>
[?x+xs xs]
(case ?x+xs
#;None (wrap init)
(#;Some [x xs']) (do @
[init' (f x init)]
(fold f init' xs')))))
(def: #export (folds f init xs)
{#;doc "A channel of folds."}
(All [a b] (-> (-> b a (&;Promise a)) a (Channel b) (Channel a)))
(do &;Monad<Promise>
[?x+xs xs]
(case ?x+xs
#;None (wrap (#;Some [init (wrap #;None)]))
(#;Some [x xs']) (do @
[init' (f x init)]
(folds f init' xs')))))
(def: (distinct' eq last-one xs)
(All [a] (-> (Eq a) a (Channel a) (Channel a)))
(let [(^open) eq]
(do &;Monad<Promise>
[?x+xs xs]
(case ?x+xs
#;None (wrap #;None)
(#;Some [x xs']) (if (= x last-one)
(distinct' eq last-one xs')
(wrap (#;Some [x (distinct' eq x xs')])))))))
(def: #export (distinct eq xs)
{#;doc "Multiple consecutive equal values in the input channel will just be single value in the output channel."}
(All [a] (-> (Eq a) (Channel a) (Channel a)))
(let [(^open) eq]
(do &;Monad<Promise>
[?x+xs xs]
(case ?x+xs
#;None (wrap #;None)
(#;Some [x xs']) (wrap (#;Some [x (distinct' eq x xs')]))))))
(def: #export (consume xs)
{#;doc "Reads the entirety of a channel's contents and returns them as a list."}
(All [a] (-> (Channel a) (&;Promise (List a))))
(do &;Monad<Promise>
[?x+xs' xs]
(case ?x+xs'
#;None
(wrap #;Nil)
(#;Some [x xs'])
(do @
[=xs (consume xs')]
(wrap (#;Cons x =xs))))))
(def: #export (once p)
(All [a] (-> (&;Promise a) (Channel a)))
(do &;Monad<Promise>
[x p]
(wrap (#;Some [x (wrap #;None)]))))
(def: #export (poll time action)
(All [a] (-> Nat (IO (Maybe a)) (Channel a)))
(do &;Monad<Promise>
[?output (&;future action)]
(case ?output
#;None
(wrap #;None)
(#;Some head)
(do @
[_ (&;wait time)]
(wrap (#;Some [head (poll time action)]))))))
(def: #export (periodic time value)
(All [a] (-> Nat a (Channel a)))
(do &;Monad<Promise>
[]
(wrap (#;Some [value (do @
[_ (&;wait time)]
(periodic time value))]))))
(def: #export (sequential time xs)
(All [a] (-> Nat (List a) (Channel a)))
(do &;Monad<Promise>
[]
(case xs
#;Nil
(wrap #;None)
(#;Cons x xs')
(wrap (#;Some [x (do @
[_ (&;wait time)]
(sequential time xs'))])))))
(def: #export (cycle time values)
(All [a] (-> Nat (List a) (Channel a)))
(do &;Monad<Promise>
[]
(case values
#;Nil
(wrap #;None)
_
(loop [xs values]
(case xs
#;Nil
(recur values)
(#;Cons x xs')
(wrap (#;Some [x (do @
[_ (&;wait time)]
(recur xs'))])))))))
## Utils
(def: (tail xs)
(All [a] (-> (List a) (List a)))
(case xs
#;Nil
#;Nil
(#;Cons _ xs')
xs'))
(def: #export (sliding-window max inputs)
(All [a] (-> Nat (Channel a) (Channel (List a))))
(let [(^open) &;Monad<Promise>]
(folds (function [input window]
(let [window' (L/compose window (list input))]
(wrap (if (n.<= max (list;size window'))
window'
(tail window')))))
(list)
inputs)))
(def: #export (iterate f init)
(All [a] (-> (-> a (&;Promise (Maybe a))) a (Channel a)))
(do &;Monad<Promise>
[]
(wrap (#;Some [init (do @
[?next (f init)]
(case ?next
#;None
(wrap #;None)
(#;Some init')
(iterate f init')))]))))
(def: #export (sample time inputs)
(All [a] (-> Nat (Channel a) (Channel a)))
(do &;Monad<Promise>
[?h+t inputs]
(case ?h+t
#;None
(wrap #;None)
(#;Some [value inputs'])
(do @
[_ (&;wait time)
#let [next-inputs (loop [last-resolved-node inputs']
(case (&;poll last-resolved-node)
(^multi (#;Some (#;Some [_ next-node]))
(&;resolved? next-node))
(recur next-node)
_
last-resolved-node))]]
(wrap (#;Some [value (sample time next-inputs)]))))))
## [Structures]
(struct: #export _ (F;Functor Channel)
(def: (map f xs)
(:: &;Functor<Promise> map
(function [?x+xs]
(case ?x+xs
#;None #;None
(#;Some [x xs']) (#;Some [(f x) (map f xs')])))
xs)))
(struct: #export _ (A;Applicative Channel)
(def: functor Functor<Channel>)
(def: (wrap a)
(let [(^open) &;Monad<Promise>]
(wrap (#;Some [a (wrap #;None)]))))
(def: (apply ff fa)
(let [fb (channel ($ +1))]
(exec (let [(^open) Functor<Channel>]
(map (function [f] (pipe (map f fa) fb))
ff))
fb))))
(struct: #export _ (Monad Channel)
(def: applicative Applicative<Channel>)
(def: (join mma)
(let [output (channel ($ +0))]
(exec (let [(^open) Functor<Channel>]
(map (function [ma]
(pipe ma output))
mma))
output))))
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