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|
(.module:
lux
(lux [io]
(control [functor #+ Functor]
[applicative #+ Applicative]
[monad #+ Monad do])
(concurrency [atom])
[macro #+ with-gensyms]
(macro ["s" syntax #+ syntax:])
(type abstract)))
(abstract: #export (Lazy a)
(-> [] a)
(def: (freeze' generator)
(All [a] (-> (-> [] a) (Lazy a)))
(let [cache (atom.atom (: (Maybe ($ +0)) #.None))]
(@abstract (function [_]
(case (io.run (atom.read cache))
(#.Some value)
value
_
(let [value (generator [])]
(exec (io.run (atom.compare-and-swap _ (#.Some value) cache))
value)))))))
(def: #export (thaw l-value)
(All [a] (-> (Lazy a) a))
((@repr l-value) [])))
(syntax: #export (freeze expr)
(with-gensyms [g!_]
(wrap (list (` ((~! freeze') (function [(~@ g!_)] (~ expr))))))))
(struct: #export _ (Functor Lazy)
(def: (map f fa)
(freeze (f (thaw fa)))))
(struct: #export _ (Applicative Lazy)
(def: functor Functor<Lazy>)
(def: (wrap a)
(freeze a))
(def: (apply ff fa)
(freeze ((thaw ff) (thaw fa)))))
(struct: #export _ (Monad Lazy)
(def: applicative Applicative<Lazy>)
(def: join thaw))
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