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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 (meta macro
ast)
(control (monoid #as m #refer #all)
(functor #as F #refer #all)
(monad #as M #refer #all)))
(.. list))
## [Types]
## (deftype (Maybe a)
## (| #;None
## (#;Some a)))
## [Structures]
(defstruct #export Maybe/Monoid (Monoid Maybe)
(def m;unit #;None)
(def (m;++ xs ys)
(case xs
#;None ys
(#;Some x) (#;Some x))))
(defstruct #export Maybe/Functor (Functor Maybe)
(def (F;map f ma)
(case ma
#;None #;None
(#;Some a) (#;Some (f a)))))
(defstruct #export Maybe/Monad (Monad Maybe)
(def M;_functor Maybe/Functor)
(def (M;wrap x)
(#;Some x))
(def (M;join mma)
(case mma
#;None #;None
(#;Some xs) xs)))
## [Syntax]
(defmacro #export (? tokens state)
(case tokens
(\ (list maybe else))
(let [g!value (symbol$ ["" "_"])]
(#;Right state (list (` (case (~ maybe)
(#;Some (~ g!value))
(~ g!value)
_
(~ else))))))
_
(#;Left "Wrong syntax for ?")))
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