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## Copyright (c) Eduardo Julian. All rights reserved.
## The use and distribution terms for this software are covered by the
## Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
## which can be found in the file epl-v10.html at the root of this distribution.
## By using this software in any fashion, you are agreeing to be bound by
## the terms of this license.
## You must not remove this notice, or any other, from this software.
(;import lux
(lux/data state))
## Signatures
(defsig #export (Functor f)
(: (All [a b]
(-> (-> a b) (f a) (f b)))
map))
## Structures
(defstruct #export Maybe:Functor (Functor Maybe)
(def (map f ma)
(case ma
#;None #;None
(#;Some a) (#;Some (f a)))))
(defstruct #export List:Functor (Functor List)
(def (map f ma)
(case ma
#;Nil #;Nil
(#;Cons [a ma']) (#;Cons [(f a) (map f ma')]))))
(defstruct #export State:Functor (Functor State)
(def (map f ma)
(lambda [state]
(let [[state' a] (ma state)]
[state' (f a)]))))
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