diff options
Diffstat (limited to 'libraries/base/System/Timeout.hs')
| -rw-r--r-- | libraries/base/System/Timeout.hs | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/libraries/base/System/Timeout.hs b/libraries/base/System/Timeout.hs index d34082e64f..e2b85658bb 100644 --- a/libraries/base/System/Timeout.hs +++ b/libraries/base/System/Timeout.hs @@ -35,9 +35,9 @@ import Data.Unique (Unique, newUnique) -- interrupt the running IO computation when the timeout has -- expired. -newtype Timeout = Timeout Unique deriving (Eq) +newtype Timeout = Timeout Unique deriving Eq -- ^ @since 4.0 --- | @since 3.0 +-- | @since 4.0 instance Show Timeout where show _ = "<<timeout>>" @@ -53,6 +53,12 @@ instance Exception Timeout where -- timeout interval means \"wait indefinitely\". When specifying long timeouts, -- be careful not to exceed @maxBound :: Int@. -- +-- >>> timeout 1000000 (threadDelay 1000 *> pure "finished on time") +-- Just "finished on time" +-- +-- >>> timeout 10000 (threadDelay 100000 *> pure "finished on time") +-- Nothing +-- -- The design of this combinator was guided by the objective that @timeout n f@ -- should behave exactly the same as @f@ as long as @f@ doesn't time out. This -- means that @f@ has the same 'myThreadId' it would have without the timeout @@ -75,7 +81,6 @@ instance Exception Timeout where -- because the runtime system uses scheduling mechanisms like @select(2)@ to -- perform asynchronous I\/O, so it is possible to interrupt standard socket -- I\/O or file I\/O using this combinator. - timeout :: Int -> IO a -> IO (Maybe a) timeout n f | n < 0 = fmap Just f |