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|
(.module:
[library
[lux #*
[abstract
[functor (#+ Functor)]
[apply (#+ Apply)]
[monad (#+ Monad do)]
[equivalence (#+ Equivalence)]]
[control
["." io]
[parser
["<.>" code]]
[concurrency
["." atom]]]
[macro (#+ with_identifiers)
[syntax (#+ syntax:)]]
[type
abstract]]])
(abstract: .public (Lazy a)
{}
(-> [] a)
(def: (lazy' 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: .public (value lazy)
(All [a] (-> (Lazy a) a))
((:representation lazy) [])))
(syntax: .public (lazy [expression <code>.any])
(with_identifiers [g!_]
(in (list (` ((~! lazy') (function ((~ g!_) (~ g!_)) (~ expression))))))))
(implementation: .public (equivalence (^open "\."))
(All [a] (-> (Equivalence a) (Equivalence (Lazy a))))
(def: (= left right)
(\= (..value left)
(..value right))))
(implementation: .public functor
(Functor Lazy)
(def: (map f fa)
(lazy (f (value fa)))))
(implementation: .public apply
(Apply Lazy)
(def: &functor ..functor)
(def: (apply ff fa)
(lazy ((value ff) (value fa)))))
(implementation: .public monad
(Monad Lazy)
(def: &functor ..functor)
(def: in (|>> lazy))
(def: join value))
|
