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|
(.module:
[lux #*
["_" test (#+ Test)]
[control
pipe
[monad (#+ do)]
{[0 #test]
[/
[".T" functor (#+ Injection Comparison)]
[".T" apply]
[".T" monad]
[".T" equivalence]]}]
[data
["." text
format]
[number
["." nat]]]
["." io ("#@." monad)]
[math
["r" random (#+ Random)]]]
{1
["." / ("#@." monoid)]})
(def: injection
(Injection Maybe)
(|>> #.Some))
(def: comparison
(Comparison Maybe)
(function (_ ==)
(:: (/.equivalence ==) =)))
(def: #export maybe
(All [a] (-> (Random a) (Random (Maybe a))))
(:: r.functor map (|>> #.Some)))
(def: #export test
Test
(<| (_.context (%name (name-of .Maybe)))
($_ _.and
(equivalenceT.test (/.equivalence nat.equivalence) (..maybe r.nat))
(functorT.laws ..injection ..comparison /.functor)
(applyT.laws ..injection ..comparison /.apply)
(monadT.laws ..injection ..comparison /.monad)
(do r.monad
[left r.nat
right r.nat
#let [expected (n/+ left right)]]
(let [lift (/.lift io.monad)]
(_.test "Can add maybe functionality to any monad."
(|> (io.run (do (/.with io.monad)
[a (lift (io@wrap left))
b (wrap right)]
(wrap (n/+ a b))))
(case> (#.Some actual)
(n/= expected actual)
_
false)))))
(let [(^open "/@.") (/.equivalence text.equivalence)
(^open "/@.") /.monoid]
(_.test "Monoid respects Maybe."
(and (/@= #.None /@identity)
(/@= (#.Some "yolo") (/@compose (#.Some "yolo") (#.Some "lol")))
(/@= (#.Some "yolo") (/@compose (#.Some "yolo") #.None))
(/@= (#.Some "lol") (/@compose #.None (#.Some "lol")))
(/@= #.None (: (Maybe Text) (/@compose #.None #.None))))))
(do r.monad
[default r.nat
value r.nat]
(_.test "Can have defaults for Maybe values."
(and (is? default (/.default default
#.None))
(is? value (/.default default
(#.Some value))))))
)))
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