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## Copyright (c) Eduardo Julian. All rights reserved.
## This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
## If a copy of the MPL was not distributed with this file,
## You can obtain one at http://mozilla.org/MPL/2.0/.
(;import lux
(lux/control (functor #as F #refer #all)
(monad #as M #refer #all)))
## [Types]
(deftype #export (State s a)
(-> s (, s a)))
## [Structures]
(defstruct #export State/Functor (Functor State)
(def (F;map f ma)
(lambda [state]
(let [[state' a] (ma state)]
[state' (f a)]))))
(defstruct #export State/Monad (All [s]
(Monad (State s)))
(def M;_functor State/Functor)
(def (M;wrap x)
(lambda [state]
[state x]))
(def (M;join mma)
(lambda [state]
(let [[state' ma] (mma state)]
(ma state')))))
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