readIO -package:ghc-prim

readIO :: Read a => String -> IO a
base Prelude System.IO, ghc-internal GHC.Internal.System.IO
The readIO function is similar to read except that it signals parse failure to the IO monad instead of terminating the program. This operation may fail with:

Examples

>>> fmap (+ 1) (readIO "1")
2

>>> readIO "not quite ()" :: IO ()
*** Exception: user error (Prelude.readIO: no parse)
readIO :: Read a => String -> IO a
hedgehog Hedgehog.Internal.Prelude, base-compat Prelude.Compat, base-prelude BasePrelude, numeric-prelude NumericPrelude NumericPrelude.Base, Cabal-syntax Distribution.Compat.Prelude, numhask NumHask.Prelude, clash-prelude Clash.HaskellPrelude, ghc-lib-parser GHC.Prelude.Basic, prelude-compat Prelude2010, pathtype System.Path.IO, dimensional Numeric.Units.Dimensional.Prelude, rebase Rebase.Prelude, mixed-types-num Numeric.MixedTypes.PreludeHiding, xmonad-contrib XMonad.Config.Prime, constrained-categories Control.Category.Constrained.Prelude Control.Category.Hask, copilot-language Copilot.Language.Prelude, LambdaHack Game.LambdaHack.Core.Prelude, cabal-install-solver Distribution.Solver.Compat.Prelude, faktory Faktory.Prelude, yesod-paginator Yesod.Paginator.Prelude, distribution-opensuse OpenSuse.Prelude, hledger-web Hledger.Web.Import
The readIO function is similar to read except that it signals parse failure to the IO monad instead of terminating the program.
readIO :: Read a => String -> IO a
ghc GHC.Prelude.Basic
readIO :: (MonadIO m, Read a) => Text -> m a
basic-prelude BasicPrelude
The readIO function is similar to read except that it signals parse failure to the IO monad instead of terminating the program.
readIORef :: IORef a -> IO a
base Data.IORef GHC.IORef, ihaskell IHaskellPrelude, ghc-internal GHC.Internal.Data.IORef GHC.Internal.IORef, rebase Rebase.Prelude
Read the value of an IORef. Beware that the CPU executing a thread can reorder reads or writes to independent locations. See Data.IORef#memmodel for more details.
readIOArray :: Ix i => IOArray i e -> i -> IO e
base GHC.IOArray, ghc-internal GHC.Internal.IOArray
Read a value from an IOArray
readIOPort :: IOPort a -> IO a
base GHC.IOPort
Atomically read the contents of the IOPort. If the IOPort is currently empty, readIOPort will wait until it is full. After a readIOPort, the IOPort is left empty. There is one important property of readIOPort:
  • Only a single threads can be blocked on an IOPort.
readIORef :: MonadIO m => IORef a -> m a
unliftio UnliftIO.IORef
Lifted readIORef.
readIORef :: MonadBase IO m => IORef a -> m a
lifted-base Data.IORef.Lifted
Generalized version of readIORef.
readIORef :: MonadIO m => IORef a -> m a
relude Relude.Lifted.IORef
Lifted version of readIORef. 
>>> ref <- newIORef 42

>>> readIORef ref
42
readIORef :: IORef a -> IO a
base-prelude BasePrelude
Read the value of an IORef
readIORef :: Unbox a => IORef a -> IO a
streamly-core Streamly.Internal.Data.IORef
Read a value from an IORef. Pre-release
readIORef :: Unbox a => IORef a -> IO a
streamly-core Streamly.Internal.Data.MutArray
Deprecated: Use readIORef from MutByteArray module.
readIORef :: MonadConc m => IORef m a -> m a
concurrency Control.Concurrent.Classy.IORef Control.Monad.Conc.Class
Read the current value stored in a reference. 
readIORef ioref = readForCAS ioref >>= peekTicket
readIORef :: MonadDejaFu n => ModelIORef n a -> ThreadId -> n a
dejafu Test.DejaFu.Conc.Internal.Memory
Read from a IORef, returning a newer thread-local non-committed write if there is one.
readIORefGlobal :: MonadDejaFu n => ModelIORef n a -> n a
dejafu Test.DejaFu.Conc.Internal.Memory
Read the global state of a IORef.
readIORefPrim :: MonadDejaFu n => ModelIORef n a -> ThreadId -> n (a, Integer)
dejafu Test.DejaFu.Conc.Internal.Memory
Read the local state of a IORef.
readIORefU :: Prim a => IORefU a -> IO a
unboxed-ref Data.IORef.Unboxed
Read the value of an IORefU
readIORef' :: IORef' a -> IO a
strict-mutable-base Data.IORef.Strict
readIORef for IORef'.
ReadIOPortOp :: PrimOp
ghc GHC.Builtin.PrimOps, ghc-lib-parser GHC.Builtin.PrimOps
ReadIORef :: IORefId -> ThreadAction
dejafu Test.DejaFu.Conc Test.DejaFu.Types
Read from a IORef.
ReadIORefCas :: IORefId -> ThreadAction
dejafu Test.DejaFu.Conc Test.DejaFu.Types
Read from a IORef for a future compare-and-swap.
unsafeReadIOArray :: IOArray i e -> Int -> IO e
base GHC.IOArray, ghc-internal GHC.Internal.IOArray
Read a value from an IOArray
WillReadIORef :: IORefId -> Lookahead
dejafu Test.DejaFu.Conc
Will read from a IORef.
WillReadIORefCas :: IORefId -> Lookahead
dejafu Test.DejaFu.Conc
Will read from a IORef for a future compare-and-swap.