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(;module:
lux
(lux (macro [ast])
(control functor
applicative
monad)
(data (coll list))
function))
## [Types]
(type: #export (Cont a)
{#;doc "Delimited continuations."}
(All [b]
(-> (-> a b) b)))
## [Syntax]
(macro: #export (@lazy tokens state)
{#;doc (doc "Delays the evaluation of an expression, by wrapping it in a continuation 'thunk'."
(@lazy (some-computation some-input)))}
(case tokens
(^ (list value))
(let [blank (ast;symbol ["" ""])]
(#;Right [state (list (` (;lambda [(~ blank)] ((~ blank) (~ value)))))]))
_
(#;Left "Wrong syntax for @lazy")))
## [Functions]
(def: #export (call/cc f)
{#;doc "Call with current continuation."}
(All [a b c]
(-> (-> (-> a (Cont b c))
(Cont a c))
(Cont a c)))
(lambda [k]
(f (lambda [a _]
(k a))
k)))
(def: #export (continue f thunk)
{#;doc "Forces a continuation thunk to be evaluated."}
(All [i o]
(-> (-> i o) (Cont i o) o))
(thunk f))
(def: #export (run thunk)
{#;doc "Forces a continuation thunk to be evaluated."}
(All [a]
(-> (Cont a) a))
(continue id thunk))
## [Structs]
(struct: #export _ (Functor Cont)
(def: (map f ma)
(lambda [k] (ma (. k f)))))
(struct: #export _ (Applicative Cont)
(def: functor Functor<Cont>)
(def: (wrap a)
(@lazy a))
(def: (apply ff fa)
(@lazy ((run ff) (run fa)))))
(struct: #export _ (Monad Cont)
(def: applicative Applicative<Cont>)
(def: join run))
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