Moduleghc-9.14.1GHC2021

GHC.Data.IOEnv

The IO Monad with an environment

The environment is passed around as a Reader monad but as its in the IO monad, mutable references can be used for updating state.

3 types
19 values

Packageghc-9.14.1
Exports22
LanguageGHC2021
LicenceBSD-3-Clause
SourceIOEnv.hs

newtypenewtype IOEnv env a

Instances22Quasi, GhcMonad, Monad, Functor, MonadFix, MonadFail, …

Quasi TcMDefined in ghc-9.14.1 · GHC.Tc.Gen.Splice · orphan
GhcMonad BkpMDefined in ghc-9.14.1 · GHC.Driver.Backpack
HasLogger BkpMDefined in ghc-9.14.1 · GHC.Driver.Backpack
HasDynFlags BkpMDefined in ghc-9.14.1 · GHC.Driver.Backpack
Monad (IOEnv m)Defined in ghc-9.14.1 · GHC.Data.IOEnv
Functor (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv
MonadFix (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv
MonadFail (IOEnv m)Defined in ghc-9.14.1 · GHC.Data.IOEnv
Applicative (IOEnv m)Defined in ghc-9.14.1 · GHC.Data.IOEnv
Alternative (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv
MonadPlus (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv
MonadIO (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv
MonadCatch (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv
MonadMask (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv
MonadThrow (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv
ContainsLogger env => HasLogger (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv
ContainsModule env => HasModule (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv
MonadUnique (IOEnv (Env gbl lcl))Defined in ghc-9.14.1 · GHC.Tc.Utils.Monad · orphan
MonadThings (IOEnv (Env DsGblEnv DsLclEnv))Defined in ghc-9.14.1 · GHC.HsToCore.Monad · orphan
MonadThings (IOEnv (Env TcGblEnv TcLclEnv))Defined in ghc-9.14.1 · GHC.Tc.Utils.Env · orphan
ContainsDynFlags env => HasDynFlags (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv
ContainsHooks env => HasHooks (IOEnv env)Defined in ghc-9.14.1 · GHC.Data.IOEnv

module GHC.Utils.Monad

valuefailM :: IOEnv env a

valuefailWithM :: String -> IOEnv env a

datadata IOEnvFailure

IOEnvFailure

Instances2Show, Exception

Show IOEnvFailureDefined in ghc-9.14.1 · GHC.Data.IOEnv
Exception IOEnvFailureDefined in ghc-9.14.1 · GHC.Data.IOEnv

valuegetEnv :: IOEnv env env

valuesetEnv :: env' -> IOEnv env' a -> IOEnv env a

Perform a computation with a different environment

valueupdEnv :: (env -> env') -> IOEnv env' a -> IOEnv env a

Perform a computation with an altered environment

valueupdEnvIO :: (env -> IO env') -> IOEnv env' a -> IOEnv env a

Perform a computation with an altered environment

valuerunIOEnv :: env -> IOEnv env a -> IO a

valueunsafeInterleaveM :: IOEnv env a -> IOEnv env a

valueuninterruptibleMaskM_ :: IOEnv env a -> IOEnv env a

valuetryM :: IOEnv env r -> IOEnv env (Either IOEnvFailure r)

valuetryAllM :: IOEnv env r -> IOEnv env (Either SomeException r)

valuetryMostM :: IOEnv env r -> IOEnv env (Either SomeException r)

valuefixM :: (a -> IOEnv env a) -> IOEnv env a

newtypenewtype IORef a

A mutable variable in the IO monad.

Example11 expressions

>>> import GHC.Internal.Data.IORef>>> r <- newIORef 0>>> readIORef r0>>> writeIORef r 1>>> readIORef r1>>> atomicWriteIORef r 2>>> readIORef r2>>> modifyIORef' r (+ 1)>>> readIORef r3>>> atomicModifyIORef' r (\a -> (a + 1, ()))>>> readIORef r4