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|
(.require
[library
[lux (.except list with)
[abstract
[monoid (.only Monoid)]
[equivalence (.only Equivalence)]
[hash (.only Hash)]
[apply (.only Apply)]
["[0]" functor (.only Functor)]
["[0]" monad (.only Monad do)]]
[meta
["[0]" location]]]])
... (type: (Maybe a)
... {.#None}
... {.#Some a})
(def .public monoid
(All (_ a) (Monoid (Maybe a)))
(implementation
(def identity
{.#None})
(def (composite mx my)
(case mx
{.#None}
my
_
mx))))
(def .public functor
(Functor Maybe)
(implementation
(def (each f ma)
(case ma
{.#Some a}
{.#Some (f a)}
... {.#None}
it
(as_expected it)))))
(def .public apply
(Apply Maybe)
(implementation
(def functor ..functor)
(def (on fa ff)
(case [ff fa]
[{.#Some f} {.#Some a}]
{.#Some (f a)}
_
{.#None}))))
(def .public monad
(Monad Maybe)
(implementation
(def functor ..functor)
(def (in x)
{.#Some x})
(def (conjoint mma)
(case mma
{.#Some mx}
mx
... {.#None}
it
(as_expected it)))))
(def .public (equivalence super)
(All (_ a) (-> (Equivalence a) (Equivalence (Maybe a))))
(implementation
(def (= mx my)
(case [mx my]
[{.#None} {.#None}]
#1
[{.#Some x} {.#Some y}]
(at super = x y)
_
#0))))
(def .public (hash super)
(All (_ a) (-> (Hash a) (Hash (Maybe a))))
(implementation
(def equivalence
(..equivalence (at super equivalence)))
(def (hash value)
(case value
{.#None}
1
{.#Some value}
(at super hash value)))))
(def .public (with monad)
(All (_ M) (-> (Monad M) (Monad (All (_ a) (M (Maybe a))))))
(implementation
(def functor
(functor.composite (the monad.functor monad)
..functor))
(def in
(|>> (at ..monad in)
(at monad in)))
(def (conjoint MmMma)
(do monad
[mMma MmMma]
(case mMma
{.#Some Mma}
Mma
... {.#None}
it
(in (as_expected it)))))))
(def .public (lifted monad)
(All (_ M a) (-> (Monad M) (-> (M a) (M (Maybe a)))))
(at monad each (at ..monad in)))
(def .public else
(macro (_ tokens state)
(case tokens
(pattern (.list else maybe))
(let [g!temp (is Code [location.dummy {.#Symbol ["" ""]}])]
{.#Right [state (.list (` (.case (~ maybe)
{.#Some (~ g!temp)}
(~ g!temp)
... {.#None}
(~ g!temp)
(~ else))))]})
_
{.#Left "Wrong syntax for 'else'"})))
(def .public trusted
(All (_ a) (-> (Maybe a) a))
(|>> (..else (undefined))))
(def .public (list value)
(All (_ a) (-> (Maybe a) (List a)))
(case value
{.#Some value}
(.list value)
... {.#None}
_
(.list)))
(def .public when
(macro (_ tokens state)
(case tokens
(pattern (.list test then))
{.#Right [state (.list (` (.if (~ test)
(~ then)
{.#None})))]}
_
{.#Left "Wrong syntax for 'when'"})))
|
