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GHC 9.10.3 · lts/ghc-9.10.x · c74966e · 2026-09-27

Moduleghc-9.10.3GHC2021

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
  • 18 values
  • Packageghc-9.10.3
  • Exports21
  • LanguageGHC2021
  • LicenceBSD-3-Clause
  • SourceIOEnv.hs
newtypenewtype IOEnv env a
#
Instances22Quasi, GhcMonad, Monad, Functor, MonadFix, MonadFail, …

module GHC.Utils.Monad

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

newtypenewtype IORef a
#

A mutable variable in the IO monad.

Example11 expressions
import GHC.Internal.Data.IORefr <- newIORef 0readIORef r0writeIORef r 1readIORef r1atomicWriteIORef r 2readIORef r2modifyIORef' r (+ 1)readIORef r3atomicModifyIORef' r (\a -> (a + 1, ()))readIORef r4

See also STRef and Control.Concurrent.MVar.MVar.

Instances3NFData1, Eq, NFData
  • NFData1 IORefDefined in deepseq-1.5.0.0 · Control.DeepSeq
  • Eq (IORef a)Defined in ghc-internal-9.1003.0 · GHC.Internal.IORef

    Pointer equality.

  • NFData (IORef a)Defined in deepseq-1.5.0.0 · Control.DeepSeq

    NOTE: Only strict in the reference and not the referenced value.