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(;module:
lux
(lux (control ["F" functor]
["A" applicative]
monad)
function
[macro #+ with-gensyms]
(macro [code]
[syntax #+ syntax:])))
(type: #export (Cont i o)
{#;doc "Continuations."}
(-> (-> i o) o))
(def: #export (continue k cont)
{#;doc "Forces a continuation thunk to be evaluated."}
(All [i o] (-> (-> i o) (Cont i o) o))
(cont k))
(def: #export (run cont)
{#;doc "Forces a continuation thunk to be evaluated."}
(All [a] (-> (Cont a a) a))
(cont id))
(struct: #export Functor<Cont> (All [o] (F;Functor (All [i] (Cont i o))))
(def: (map f fv)
(function [k] (fv (. k f)))))
(struct: #export Applicative<Cont> (All [o] (A;Applicative (All [i] (Cont i o))))
(def: functor Functor<Cont>)
(def: (wrap value)
(function [k] (k value)))
(def: (apply ff fv)
(function [k]
(|> (k (f v))
(function [v]) fv
(function [f]) ff))))
(struct: #export Monad<Cont> (All [o] (Monad (All [i] (Cont i o))))
(def: applicative Applicative<Cont>)
(def: (join ffa)
(function [k]
(ffa (continue k)))))
(def: #export (call/cc f)
{#;doc "Call with current continuation."}
(All [a b z]
(-> (-> (-> a (Cont b z))
(Cont a z))
(Cont a z)))
(function [k]
(f (function [a] (function [_] (k a)))
k)))
(syntax: #export (pending expr)
{#;doc (doc "Turns any expression into a function that is pending a continuation."
(pending (some-computation some-input)))}
(with-gensyms [g!k]
(wrap (list (` (;function [(~ g!k)] ((~ g!k) (~ expr))))))))
(def: #export (portal init)
(All [i o z]
(-> i
(Cont [(-> i (Cont o z))
i]
z)))
(call/cc (function [k]
(do Monad<Cont>
[#let [nexus (function nexus [val]
(k [nexus val]))]
_ (k [nexus init])]
(wrap (undefined))))))
(def: #export (reset scope)
(All [i o] (-> (Cont i i) (Cont i o)))
(function [k]
(k (run scope))))
(def: #export (shift f)
(All [a]
(-> (-> (-> a (Cont a a))
(Cont a a))
(Cont a a)))
(function [oc]
(f (function [a] (function [ic] (ic (oc a))))
id)))
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