:: Monoid_a _ => _ a -package:base-prelude package:stack

exitSuccess :: MonadIO m => m a
stack Stack.Prelude
Lifted version of "System.Exit.exitSuccess". @since 0.1.9.0.
exitFailure :: MonadIO m => m a
stack Stack.Prelude
Lifted version of "System.Exit.exitFailure". @since 0.1.9.0.
mzero :: MonadPlus m => m a
stack Stack.Prelude
The identity of mplus. It should also satisfy the equations 
mzero >>= f  =  mzero
v >> mzero   =  mzero
The default definition is 
mzero = empty
ask :: MonadReader r m => m r
stack Stack.Prelude
Retrieves the monad environment.