Hoogle Search

Within LTS Haskell 24.34 (ghc-9.10.3)

Note that Stackage only displays results for the latest LTS and Nightly snapshot. Learn more.

Exact lookup

1. cmap :: forall a b (m :: Type -> Type) . (a -> b) -> LogAction m b -> LogAction m a

   co-log-core	Colog.Core.Action

   This combinator is contramap from contravariant functor. It is useful when you have something like

   data LogRecord = LR
   { lrName    :: LoggerName
   , lrMessage :: Text
   }
   

   and you need to provide LogAction which consumes LogRecord

   logRecordAction :: LogAction m LogRecord
   

   when you only have action that consumes Text

   logTextAction :: LogAction m Text
   

   With cmap you can do the following:

   logRecordAction :: LogAction m LogRecord
   logRecordAction = cmap lrMesssage logTextAction
   

   This action will print only lrMessage from LogRecord. But if you have formatting function like this:

   formatLogRecord :: LogRecord -> Text
   

   you can apply it instead of lrMessage to log formatted LogRecord as Text.

2. cmapM :: Monad m => (a -> m b) -> LogAction m b -> LogAction m a

   co-log-core	Colog.Core.Action

   cmapM combinator is similar to cmap but allows to call monadic functions (functions that require extra context) to extend consumed value. Consider the following example. You have this logging record:

   data LogRecord = LR
   { lrTime    :: UTCTime
   , lrMessage :: Text
   }
   

   and you also have logging consumer inside IO for such record:

   logRecordAction :: LogAction IO LogRecord
   

   But you need to return consumer only for Text messages:

   logTextAction :: LogAction IO Text
   

   If you have function that can extend Text to LogRecord like the function below:

   withTime :: Text -> IO LogRecord
   withTime msg = do
   time <- getCurrentTime
   pure (LR time msg)
   

   you can achieve desired behavior with cmapM in the following way:

   logTextAction :: LogAction IO Text
   logTextAction = cmapM withTime myAction
   

3. cmapMaybe :: forall (m :: Type -> Type) a b . Applicative m => (a -> Maybe b) -> LogAction m b -> LogAction m a

   co-log-core	Colog.Core.Action

   cmap for convertions that may fail

4. cmapMaybeM :: Monad m => (a -> m (Maybe b)) -> LogAction m b -> LogAction m a

   co-log-core	Colog.Core.Action

   Similar to cmapMaybe but for convertions that may fail inside a monadic context.

5. concatMapMonoid :: Monoid m => (time -> m) -> (body -> m) -> T time body -> m

   event-list	Data.EventList.Absolute.TimeBody

   No documentation available.

6. concatMapMonoid :: Monoid m => (time -> m) -> (body -> m) -> T time body -> m

   event-list	Data.EventList.Absolute.TimeTime

   No documentation available.

7. concatMapMonoid :: Monoid m => (time -> m) -> (body -> m) -> T time body -> m

   event-list	Data.EventList.Relative.BodyBody

   No documentation available.

8. concatMapMonoid :: Monoid m => (time -> m) -> (body -> m) -> T time body -> m

   event-list	Data.EventList.Relative.BodyTime

   No documentation available.

9. concatMapMonoid :: Monoid m => (time -> m) -> (body -> m) -> T time body -> m

   event-list	Data.EventList.Relative.TimeBody

   No documentation available.

10. concatMapMonoid :: Monoid m => (time -> m) -> (body -> m) -> T time body -> m

    event-list	Data.EventList.Relative.TimeTime

    No documentation available.

Page 525 of many | Previous | Next