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(.module:
[library
[lux #*
[abstract
[apply (#+ Apply)]
[equivalence (#+ Equivalence)]
["." functor (#+ Functor)]
["." monad (#+ Monad do)]]
[meta
["." location]]]])
(type: #export (Try a)
(#Failure Text)
(#Success a))
(implementation: #export functor
(Functor Try)
(def: (map f ma)
(case ma
(#Failure msg)
(#Failure msg)
(#Success datum)
(#Success (f datum)))))
(implementation: #export apply
(Apply Try)
(def: &functor ..functor)
(def: (apply ff fa)
(case ff
(#Success f)
(case fa
(#Success a)
(#Success (f a))
(#Failure msg)
(#Failure msg))
(#Failure msg)
(#Failure msg))
))
(implementation: #export monad
(Monad Try)
(def: &functor ..functor)
(def: (wrap a)
(#Success a))
(def: (join mma)
(case mma
(#Failure msg)
(#Failure msg)
(#Success ma)
ma)))
(implementation: #export (with monad)
## TODO: Replace (All [a] (M (Try a))) with (functor.Then M Try)
(All [M] (-> (Monad M) (Monad (All [a] (M (Try a))))))
(def: &functor (functor.compose (get@ #monad.&functor monad) ..functor))
(def: wrap (|>> (\ ..monad wrap) (\ monad wrap)))
(def: (join MeMea)
(do monad
[eMea MeMea]
(case eMea
(#Failure try)
(wrap (#Failure try))
(#Success Mea)
Mea))))
(def: #export (lift monad)
(All [M a] (-> (Monad M) (-> (M a) (M (Try a)))))
(\ monad map (\ ..monad wrap)))
(implementation: #export (equivalence (^open "_\."))
(All [a] (-> (Equivalence a) (Equivalence (Try a))))
(def: (= reference sample)
(case [reference sample]
[(#Success reference) (#Success sample)]
(_\= reference sample)
[(#Failure reference) (#Failure sample)]
("lux text =" reference sample)
_
false
)))
(def: #export (succeed value)
(All [a] (-> a (Try a)))
(#Success value))
(def: #export (fail message)
(-> Text Try)
(#Failure message))
(def: #export (assume try)
(All [a] (-> (Try a) a))
(case try
(#Success value)
value
(#Failure message)
(error! message)))
(def: #export (to_maybe try)
(All [a] (-> (Try a) (Maybe a)))
(case try
(#Success value)
(#.Some value)
(#Failure message)
#.None))
(def: #export (from_maybe maybe)
(All [a] (-> (Maybe a) (Try a)))
(case maybe
(#.Some value)
(#Success value)
#.None
(#Failure (`` (("lux in-module" (~~ (static .prelude_module)) .name\encode)
(name_of ..from_maybe))))))
(macro: #export (default tokens compiler)
{#.doc (doc "Allows you to provide a default value that will be used"
"if a (Try x) value turns out to be #Failure."
"Note: the expression for the default value will not be computed if the base computation succeeds."
(= "bar"
(default "foo" (#..Success "bar")))
(= "foo"
(default "foo" (#..Failure "KABOOM!"))))}
(case tokens
(^ (list else try))
(#Success [compiler (list (` (case (~ try)
(#..Success (~' g!temp))
(~' g!temp)
(#..Failure (~ [location.dummy (#.Identifier ["" ""])]))
(~ else))))])
_
(#Failure "Wrong syntax for default")))
|
