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|
(.module:
[lux #*
["." io]
[control
[functor (#+ Functor)]
[apply (#+ Apply)]
[monad (#+ Monad do)]]
[concurrency
["." atom]]
[macro (#+ with-gensyms)
["s" syntax (#+ syntax:)]]
[type
abstract]])
(abstract: #export (Lazy a)
(-> [] a)
(def: (freeze' generator)
(All [a] (-> (-> [] a) (Lazy a)))
(let [cache (atom.atom #.None)]
(:abstraction (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))
((:representation l-value) [])))
(syntax: #export (freeze expr)
(with-gensyms [g!_]
(wrap (list (` ((~! freeze') (function ((~ g!_) (~ g!_)) (~ expr))))))))
(structure: #export functor (Functor Lazy)
(def: (map f fa)
(freeze (f (thaw fa)))))
(structure: #export apply (Apply Lazy)
(def: &functor ..functor)
(def: (apply ff fa)
(freeze ((thaw ff) (thaw fa)))))
(structure: #export monad (Monad Lazy)
(def: &functor ..functor)
(def: wrap (|>> freeze))
(def: join thaw))
|
