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|
(.module:
{#.doc "A method for abstracting I/O and effectful computations to make it safe while writing pure functional code."}
[library
[lux #*
[abstract
[functor (#+ Functor)]
[apply (#+ Apply)]
[monad (#+ Monad do)]]
[control
[parser
["s" code]]]
[type
abstract]
[macro (#+ with_gensyms)
[syntax (#+ syntax:)]
["." template]]]])
(abstract: #export (IO a)
(-> Any a)
{#.doc "A type that represents synchronous, effectful computations that may interact with the outside world."}
(def: label
(All [a] (-> (-> Any a) (IO a)))
(|>> :abstraction))
(template: (!io computation)
(:abstraction (template.with_locals [g!func g!arg]
(function (g!func g!arg)
computation))))
(template: (!run io)
## creatio ex nihilo
((:representation io) []))
(syntax: #export (io computation)
{#.doc (doc "Delays the evaluation of an expression, by wrapping it in an IO 'thunk'."
"Great for wrapping effectful computations (which will not be performed until the IO is 'run')."
(io (exec
(log! msg)
"Some value...")))}
(with_gensyms [g!func g!arg]
(in (list (` ((~! ..label) (function ((~ g!func) (~ g!arg))
(~ computation))))))))
(def: #export run
{#.doc "A way to execute IO computations and perform their side-effects."}
(All [a] (-> (IO a) a))
(|>> !run))
(implementation: #export functor
(Functor IO)
(def: (map f)
(|>> !run f !io)))
(implementation: #export apply
(Apply IO)
(def: &functor ..functor)
(def: (apply ff fa)
(!io ((!run ff) (!run fa)))))
(implementation: #export monad
(Monad IO)
(def: &functor ..functor)
(def: in (|>> !io))
(def: join (|>> !run !run !io)))
)
|
