mirror of
https://github.com/roc-lang/roc.git
synced 2025-09-27 13:59:08 +00:00
92 lines
2.3 KiB
Text
92 lines
2.3 KiB
Text
interface Task
|
|
exposes [ Task, succeed, fail, after, map, putLine, putInt, getInt, forever, loop ]
|
|
imports [ pf.Effect ]
|
|
|
|
Task ok err : Effect.Effect (Result ok err)
|
|
|
|
forever : Task val err -> Task * err
|
|
forever = \task ->
|
|
looper = \{ } ->
|
|
task
|
|
|> Effect.map
|
|
\res ->
|
|
when res is
|
|
Ok _ ->
|
|
Step {}
|
|
|
|
Err e ->
|
|
Done (Err e)
|
|
|
|
Effect.loop {} looper
|
|
|
|
loop : state, (state -> Task [ Step state, Done done ] err) -> Task done err
|
|
loop = \state, step ->
|
|
looper = \current ->
|
|
step current
|
|
|> Effect.map
|
|
\res ->
|
|
when res is
|
|
Ok (Step newState) ->
|
|
Step newState
|
|
|
|
Ok (Done result) ->
|
|
Done (Ok result)
|
|
|
|
Err e ->
|
|
Done (Err e)
|
|
|
|
Effect.loop state looper
|
|
|
|
succeed : val -> Task val *
|
|
succeed = \val ->
|
|
Effect.always (Ok val)
|
|
|
|
fail : err -> Task * err
|
|
fail = \val ->
|
|
Effect.always (Err val)
|
|
|
|
after : Task a err, (a -> Task b err) -> Task b err
|
|
after = \effect, transform ->
|
|
Effect.after
|
|
effect
|
|
\result ->
|
|
when result is
|
|
Ok a ->
|
|
transform a
|
|
|
|
Err err ->
|
|
Task.fail err
|
|
|
|
map : Task a err, (a -> b) -> Task b err
|
|
map = \effect, transform ->
|
|
Effect.map
|
|
effect
|
|
\result ->
|
|
when result is
|
|
Ok a ->
|
|
Ok (transform a)
|
|
|
|
Err err ->
|
|
Err err
|
|
|
|
putLine : Str -> Task {} *
|
|
putLine = \line -> Effect.map (Effect.putLine line) (\_ -> Ok {})
|
|
|
|
putInt : I64 -> Task {} *
|
|
putInt = \line -> Effect.map (Effect.putInt line) (\_ -> Ok {})
|
|
|
|
getInt : Task I64 []
|
|
getInt =
|
|
Effect.after
|
|
Effect.getInt
|
|
\{ isError, value, errorCode } ->
|
|
when isError is
|
|
True ->
|
|
when errorCode is
|
|
# A -> Task.fail InvalidCharacter
|
|
# B -> Task.fail IOError
|
|
_ ->
|
|
Task.succeed -1
|
|
|
|
False ->
|
|
Task.succeed value
|