roc/examples/cli/platform/Task.roc
2021-08-21 21:14:30 -04:00

44 lines
1.1 KiB
Text

interface Task
exposes [ Task, succeed, fail, await, map, onFail, attempt ]
imports [ fx.Effect ]
Task ok err : Effect.Effect (Result ok err)
succeed : val -> Task val *
succeed = \val ->
Effect.always (Ok val)
fail : err -> Task * err
fail = \val ->
Effect.always (Err val)
attempt : Task a b, (Result a b -> Task c d) -> Task c d
attempt = \effect, transform ->
Effect.after effect \result ->
when result is
Ok ok -> transform (Ok ok)
Err err -> transform (Err err)
await : Task a err, (a -> Task b err) -> Task b err
await = \effect, transform ->
Effect.after effect \result ->
when result is
Ok a -> transform a
Err err -> Task.fail err
onFail : Task ok a, (a -> Task ok b) -> Task ok b
onFail = \effect, transform ->
Effect.after effect \result ->
when result is
Ok a -> Task.succeed a
Err err -> transform err
map : Task a err, (a -> b) -> Task b err
map = \effect, transform ->
Effect.after effect \result ->
when result is
Ok a -> Task.succeed (transform a)
Err err -> Task.fail err