Copyright	(c) The University of Glasgow 2001-2009
License	BSD-style (see the file LICENSE)
Maintainer	libraries@haskell.org
Stability	stable
Portability	portable
Safe Haskell	Trustworthy
Language	Haskell2010

Control.DeepSeq

Contents

NFData class
Helper functions
Liftings of the NFData class
- For unary constructors
- For binary constructors

Description

This module provides overloaded functions, such as deepseq and rnf, for fully evaluating data structures (that is, evaluating to "Normal Form").

A typical use is to prevent resource leaks in lazy IO programs, by forcing all characters from a file to be read. For example:

import System.IO
import Control.DeepSeq
import Control.Exception (evaluate)

readFile' :: FilePath -> IO String
readFile' fn = do
    h <- openFile fn ReadMode
    s <- hGetContents h
    evaluate (rnf s)
    hClose h
    return s

Note: The example above should rather be written in terms of bracket to ensure releasing file-descriptors in a timely matter (see the description of force for an example).

deepseq differs from seq as it traverses data structures deeply, for example, seq will evaluate only to the first constructor in the list:

> [1,2,undefined] `seq` 3
3

While deepseq will force evaluation of all the list elements:

> [1,2,undefined] `deepseq` 3
*** Exception: Prelude.undefined

Another common use is to ensure any exceptions hidden within lazy fields of a data structure do not leak outside the scope of the exception handler, or to force evaluation of a data structure in one thread, before passing to another thread (preventing work moving to the wrong threads).

Since: deepseq-1.1.0.0

Synopsis

class NFData a where
- rnf :: a -> ()
deepseq :: NFData a => a -> b -> b
force :: NFData a => a -> a
($!!) :: NFData a => (a -> b) -> a -> b
(<$!!>) :: (Monad m, NFData b) => (a -> b) -> m a -> m b
rwhnf :: a -> ()
newtype Unit = Unit {
- runUnit :: ()
}
class (forall a. NFData a => NFData (f a)) => NFData1 (f :: Type -> Type) where
- liftRnf :: (a -> ()) -> f a -> ()
rnf1 :: (NFData1 f, NFData a) => f a -> ()
class (forall a. NFData a => NFData1 (p a)) => NFData2 (p :: Type -> Type -> Type) where
- liftRnf2 :: (a -> ()) -> (b -> ()) -> p a b -> ()
rnf2 :: (NFData2 p, NFData a, NFData b) => p a b -> ()

`NFData` class

class NFData a where Source #

A class of types that can be fully evaluated.

Since: deepseq-1.1.0.0

Minimal complete definition

Nothing

Methods

rnf :: a -> () Source #

rnf should reduce its argument to normal form (that is, fully evaluate all sub-components), and then return ().

`Generic` `NFData` deriving

Starting with GHC 7.2, you can automatically derive instances for types possessing a Generic instance.

Note: Generic1 can be auto-derived starting with GHC 7.4

{-# LANGUAGE DeriveGeneric #-}

import GHC.Generics (Generic, Generic1)
import Control.DeepSeq

data Foo a = Foo a String
             deriving (Eq, Generic, Generic1)

instance NFData a => NFData (Foo a)
instance NFData1 Foo

data Colour = Red | Green | Blue
              deriving Generic

instance NFData Colour

Starting with GHC 7.10, the example above can be written more concisely by enabling the new DeriveAnyClass extension:

{-# LANGUAGE DeriveGeneric, DeriveAnyClass #-}

import GHC.Generics (Generic)
import Control.DeepSeq

data Foo a = Foo a String
             deriving (Eq, Generic, Generic1, NFData, NFData1)

data Colour = Red | Green | Blue
              deriving (Generic, NFData)

Compatibility with previous `deepseq` versions

Prior to version 1.4.0.0, the default implementation of the rnf method was defined as

rnf a = seq a ()

However, starting with deepseq-1.4.0.0, the default implementation is based on DefaultSignatures allowing for more accurate auto-derived NFData instances. If you need the previously used exact default rnf method implementation semantics, use

instance NFData Colour where rnf x = seq x ()

or alternatively

instance NFData Colour where rnf = rwhnf

or

{-# LANGUAGE BangPatterns #-}
instance NFData Colour where rnf !_ = ()

default rnf :: (Generic a, GNFData Zero (Rep a)) => a -> () Source #

Instances

Instances details

NFData ByteArray Source #	Since: deepseq-1.4.7.0
Instance details Defined in Control.DeepSeq Methods rnf :: ByteArray -> () Source #
NFData All Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: All -> () Source #
NFData Any Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Any -> () Source #
NFData TypeRep Source #	NOTE: Prior to `deepseq-1.4.4.0` this instance was only defined for `base-4.8.0.0` and later. Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: TypeRep -> () Source #
NFData Unique Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Unique -> () Source #
NFData Version Source #	Since: deepseq-1.3.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Version -> () Source #
NFData CBool Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods rnf :: CBool -> () Source #
NFData CChar Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CChar -> () Source #
NFData CClock Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CClock -> () Source #
NFData CDouble Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CDouble -> () Source #
NFData CFile Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CFile -> () Source #
NFData CFloat Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CFloat -> () Source #
NFData CFpos Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CFpos -> () Source #
NFData CInt Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CInt -> () Source #
NFData CIntMax Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CIntMax -> () Source #
NFData CIntPtr Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CIntPtr -> () Source #
NFData CJmpBuf Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CJmpBuf -> () Source #
NFData CLLong Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CLLong -> () Source #
NFData CLong Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CLong -> () Source #
NFData CPtrdiff Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CPtrdiff -> () Source #
NFData CSChar Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CSChar -> () Source #
NFData CSUSeconds Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CSUSeconds -> () Source #
NFData CShort Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CShort -> () Source #
NFData CSigAtomic Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CSigAtomic -> () Source #
NFData CSize Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CSize -> () Source #
NFData CTime Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CTime -> () Source #
NFData CUChar Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CUChar -> () Source #
NFData CUInt Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CUInt -> () Source #
NFData CUIntMax Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CUIntMax -> () Source #
NFData CUIntPtr Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CUIntPtr -> () Source #
NFData CULLong Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CULLong -> () Source #
NFData CULong Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CULong -> () Source #
NFData CUSeconds Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CUSeconds -> () Source #
NFData CUShort Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CUShort -> () Source #
NFData CWchar Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: CWchar -> () Source #
NFData Void Source #	Defined as `rnf = absurd`. Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Void -> () Source #
NFData ThreadId Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: ThreadId -> () Source #
NFData Fingerprint Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Fingerprint -> () Source #
NFData MaskingState Source #	Since: deepseq-1.4.4.0
Instance details Defined in Control.DeepSeq Methods rnf :: MaskingState -> () Source #
NFData ExitCode Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: ExitCode -> () Source #
NFData Int16 Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Int16 -> () Source #
NFData Int32 Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Int32 -> () Source #
NFData Int64 Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Int64 -> () Source #
NFData Int8 Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Int8 -> () Source #
NFData CallStack Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: CallStack -> () Source #
NFData SrcLoc Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: SrcLoc -> () Source #
NFData Word16 Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Word16 -> () Source #
NFData Word32 Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Word32 -> () Source #
NFData Word64 Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Word64 -> () Source #
NFData Word8 Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Word8 -> () Source #
NFData Module Source #	Since: deepseq-1.4.8.0
Instance details Defined in Control.DeepSeq Methods rnf :: Module -> () Source #
NFData Ordering Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Ordering -> () Source #
NFData TyCon Source #	NOTE: Prior to `deepseq-1.4.4.0` this instance was only defined for `base-4.8.0.0` and later. Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: TyCon -> () Source #
NFData Integer Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Integer -> () Source #
NFData Natural Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Natural -> () Source #
NFData () Source #
Instance details Defined in Control.DeepSeq Methods rnf :: () -> () Source #
NFData Bool Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Bool -> () Source #
NFData Char Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Char -> () Source #
NFData Double Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Double -> () Source #
NFData Float Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Float -> () Source #
NFData Int Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Int -> () Source #
NFData Word Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Word -> () Source #
NFData a => NFData (ZipList a) Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: ZipList a -> () Source #
NFData (MutableByteArray s) Source #	Since: deepseq-1.4.8.0
Instance details Defined in Control.DeepSeq Methods rnf :: MutableByteArray s -> () Source #
NFData a => NFData (Complex a) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Complex a -> () Source #
NFData a => NFData (Identity a) Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Identity a -> () Source #
NFData a => NFData (First a) Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: First a -> () Source #
NFData a => NFData (Last a) Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Last a -> () Source #
NFData a => NFData (Down a) Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Down a -> () Source #
NFData a => NFData (First a) Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: First a -> () Source #
NFData a => NFData (Last a) Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: Last a -> () Source #
NFData a => NFData (Max a) Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: Max a -> () Source #
NFData a => NFData (Min a) Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: Min a -> () Source #
NFData m => NFData (WrappedMonoid m) Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: WrappedMonoid m -> () Source #
NFData a => NFData (Dual a) Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Dual a -> () Source #
NFData a => NFData (Product a) Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Product a -> () Source #
NFData a => NFData (Sum a) Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Sum a -> () Source #
NFData a => NFData (NonEmpty a) Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: NonEmpty a -> () Source #
NFData (IORef a) Source #	NOTE: Only strict in the reference and not the referenced value. Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: IORef a -> () Source #
NFData (MVar a) Source #	NOTE: Only strict in the reference and not the referenced value. Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: MVar a -> () Source #
NFData (FunPtr a) Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: FunPtr a -> () Source #
NFData (Ptr a) Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: Ptr a -> () Source #
NFData a => NFData (Ratio a) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Ratio a -> () Source #
NFData (StableName a) Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: StableName a -> () Source #
NFData a => NFData (Maybe a) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Maybe a -> () Source #
NFData a => NFData (Solo a) Source #	Since: deepseq-1.4.6.0
Instance details Defined in Control.DeepSeq Methods rnf :: Solo a -> () Source #
NFData a => NFData [a] Source #
Instance details Defined in Control.DeepSeq Methods rnf :: [a] -> () Source #
(NFData a, NFData b) => NFData (Either a b) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Either a b -> () Source #
NFData (Fixed a) Source #	Since: deepseq-1.3.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Fixed a -> () Source #
NFData (Proxy a) Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Proxy a -> () Source #
(NFData a, NFData b) => NFData (Arg a b) Source #	Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: Arg a b -> () Source #
NFData (TypeRep a) Source #	Since: deepseq-1.4.8.0
Instance details Defined in Control.DeepSeq Methods rnf :: TypeRep a -> () Source #
(NFData a, NFData b) => NFData (Array a b) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: Array a b -> () Source #
NFData (STRef s a) Source #	NOTE: Only strict in the reference and not the referenced value. Since: deepseq-1.4.2.0
Instance details Defined in Control.DeepSeq Methods rnf :: STRef s a -> () Source #
(NFData a, NFData b) => NFData (a, b) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: (a, b) -> () Source #
NFData (a -> b) Source #	This instance is for convenience and consistency with `seq`. This assumes that WHNF is equivalent to NF for functions. Since: deepseq-1.3.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: (a -> b) -> () Source #
NFData a => NFData (Const a b) Source #	Since: deepseq-1.4.0.0
Instance details Defined in Control.DeepSeq Methods rnf :: Const a b -> () Source #
NFData (a :~: b) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods rnf :: (a :~: b) -> () Source #
(NFData a1, NFData a2, NFData a3) => NFData (a1, a2, a3) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: (a1, a2, a3) -> () Source #
(NFData (f a), NFData (g a)) => NFData (Product f g a) Source #	Note: in `deepseq-1.5.0.0` this instance's superclasses were changed. Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods rnf :: Product f g a -> () Source #
(NFData (f a), NFData (g a)) => NFData (Sum f g a) Source #	Note: in `deepseq-1.5.0.0` this instance's superclasses were changed. Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods rnf :: Sum f g a -> () Source #
NFData (a :~~: b) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods rnf :: (a :~~: b) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4) => NFData (a1, a2, a3, a4) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: (a1, a2, a3, a4) -> () Source #
NFData (f (g a)) => NFData (Compose f g a) Source #	Note: in `deepseq-1.5.0.0` this instance's superclasses were changed. Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods rnf :: Compose f g a -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5) => NFData (a1, a2, a3, a4, a5) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: (a1, a2, a3, a4, a5) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6) => NFData (a1, a2, a3, a4, a5, a6) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: (a1, a2, a3, a4, a5, a6) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7) => NFData (a1, a2, a3, a4, a5, a6, a7) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: (a1, a2, a3, a4, a5, a6, a7) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7, NFData a8) => NFData (a1, a2, a3, a4, a5, a6, a7, a8) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: (a1, a2, a3, a4, a5, a6, a7, a8) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7, NFData a8, NFData a9) => NFData (a1, a2, a3, a4, a5, a6, a7, a8, a9) Source #
Instance details Defined in Control.DeepSeq Methods rnf :: (a1, a2, a3, a4, a5, a6, a7, a8, a9) -> () Source #

Helper functions

deepseq :: NFData a => a -> b -> b infixr 0 Source #

deepseq: fully evaluates the first argument, before returning the second.

The name deepseq is used to illustrate the relationship to seq: where seq is shallow in the sense that it only evaluates the top level of its argument, deepseq traverses the entire data structure evaluating it completely.

deepseq can be useful for forcing pending exceptions, eradicating space leaks, or forcing lazy I/O to happen. It is also useful in conjunction with parallel Strategies (see the parallel package).

There is no guarantee about the ordering of evaluation. The implementation may evaluate the components of the structure in any order or in parallel. To impose an actual order on evaluation, use pseq from Control.Parallel in the parallel package.

Since: deepseq-1.1.0.0

force :: NFData a => a -> a Source #

A variant of deepseq that is useful in some circumstances:

force x = x `deepseq` x

force x fully evaluates x, and then returns it. Note that force x only performs evaluation when the value of force x itself is demanded, so essentially it turns shallow evaluation into deep evaluation.

force can be conveniently used in combination with ViewPatterns:

{-# LANGUAGE BangPatterns, ViewPatterns #-}
import Control.DeepSeq

someFun :: ComplexData -> SomeResult
someFun (force -> !arg) = {- 'arg' will be fully evaluated -}

Another useful application is to combine force with evaluate in order to force deep evaluation relative to other IO operations:

import Control.Exception (evaluate)
import Control.DeepSeq

main = do
  result <- evaluate $ force $ pureComputation
  {- 'result' will be fully evaluated at this point -}
  return ()

Finally, here's an exception safe variant of the readFile' example:

readFile' :: FilePath -> IO String
readFile' fn = bracket (openFile fn ReadMode) hClose $ \h ->
                       evaluate . force =<< hGetContents h

Since: deepseq-1.2.0.0

($!!) :: NFData a => (a -> b) -> a -> b infixr 0 Source #

The deep analogue of $!. f $!! x fully evaluates x before returning f x.

There is no guarantee about the ordering of evaluation. f x may be evaluated before x is fully evaluated. To impose an actual order on evaluation, use pseq from Control.Parallel in the parallel package.

Since: deepseq-1.2.0.0

(<$!!>) :: (Monad m, NFData b) => (a -> b) -> m a -> m b infixl 4 Source #

Deeply strict version of <$>.

Since: deepseq-1.4.3.0

rwhnf :: a -> () Source #

Reduce to weak head normal form

Equivalent to \x -> seq x ().

Useful for defining NFData for types for which NF=WHNF holds.

data T = C1 | C2 | C3
instance NFData T where rnf = rwhnf

Since: deepseq-1.4.3.0

newtype Unit Source #

A monoid with (<>) = seq.

Its purpose is to allow reducing structures to normal form using foldMap-like functions.

Examples

Expand

data Three a = Three a a a

instance Foldable Three where
  foldMap f (Three x1 x2 x3) = f x1 <> f x2 <> f x3

instance NFData a => NFData (Three a) where
  rnf = runUnit . foldMap (Unit . rnf)

data Tree a b
  = NodeA a [Tree a b]
  | NodeB b [Tree a b]

foldMapTree :: Monoid m => (a -> m) -> (b -> m) -> Tree a b -> m
foldMapTree f g = go
  where
    go (NodeA x ts) = f x <> foldMap go ts
    go (NodeB y ts) = g y <> foldMap go ts

instance NFData2 Tree where
  liftRnf2 r r' = runUnit . foldMapTree (Unit . r) (Unit . r')

Constructors

Unit
Fields runUnit :: ()

Instances

Instances details

Monoid Unit Source #
Instance details Defined in Control.DeepSeq Methods mempty :: Unit Source # mappend :: Unit -> Unit -> Unit Source # mconcat :: [Unit] -> Unit Source #
Semigroup Unit Source #
Instance details Defined in Control.DeepSeq Methods (<>) :: Unit -> Unit -> Unit Source # sconcat :: NonEmpty Unit -> Unit Source # stimes :: Integral b => b -> Unit -> Unit Source #

Liftings of the `NFData` class

For unary constructors

class (forall a. NFData a => NFData (f a)) => NFData1 (f :: Type -> Type) where Source #

A class of functors that can be fully evaluated.

In `deepseq-1.5.0.0` this class was updated to include superclasses.

Since: deepseq-1.4.3.0

Minimal complete definition

Nothing

Methods

liftRnf :: (a -> ()) -> f a -> () Source #

liftRnf should reduce its argument to normal form (that is, fully evaluate all sub-components), given an argument to reduce a arguments, and then return ().

See rnf for the generic deriving.

default liftRnf :: (Generic1 f, GNFData One (Rep1 f)) => (a -> ()) -> f a -> () Source #

Instances

Instances details

NFData1 ZipList Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> ZipList a -> () Source #
NFData1 Identity Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Identity a -> () Source #
NFData1 First Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> First a -> () Source #
NFData1 Last Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Last a -> () Source #
NFData1 Down Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Down a -> () Source #
NFData1 First Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> First a -> () Source #
NFData1 Last Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Last a -> () Source #
NFData1 Max Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Max a -> () Source #
NFData1 Min Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Min a -> () Source #
NFData1 WrappedMonoid Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> WrappedMonoid a -> () Source #
NFData1 Dual Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Dual a -> () Source #
NFData1 Product Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Product a -> () Source #
NFData1 Sum Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Sum a -> () Source #
NFData1 NonEmpty Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> NonEmpty a -> () Source #
NFData1 IORef Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> IORef a -> () Source #
NFData1 MVar Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> MVar a -> () Source #
NFData1 FunPtr Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> FunPtr a -> () Source #
NFData1 Ptr Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Ptr a -> () Source #
NFData1 Ratio Source #	Available on `base >=4.9` Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Ratio a -> () Source #
NFData1 StableName Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> StableName a -> () Source #
NFData1 Maybe Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Maybe a -> () Source #
NFData1 Solo Source #	Since: deepseq-1.4.6.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Solo a -> () Source #
NFData1 [] Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> [a] -> () Source #
NFData a => NFData1 (Either a) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a0 -> ()) -> Either a a0 -> () Source #
NFData1 (Fixed :: Type -> Type) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Fixed a -> () Source #
NFData1 (Proxy :: Type -> Type) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Proxy a -> () Source #
NFData a => NFData1 (Arg a) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a0 -> ()) -> Arg a a0 -> () Source #
NFData a => NFData1 (Array a) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a0 -> ()) -> Array a a0 -> () Source #
NFData1 (STRef s) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> STRef s a -> () Source #
NFData a => NFData1 ((,) a) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a0 -> ()) -> (a, a0) -> () Source #
NFData a => NFData1 (Const a :: Type -> Type) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a0 -> ()) -> Const a a0 -> () Source #
NFData1 ((:~:) a) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a0 -> ()) -> (a :~: a0) -> () Source #
(NFData a1, NFData a2) => NFData1 ((,,) a1 a2) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> (a1, a2, a) -> () Source #
(NFData1 f, NFData1 g) => NFData1 (Product f g) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Product f g a -> () Source #
(NFData1 f, NFData1 g) => NFData1 (Sum f g) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Sum f g a -> () Source #
NFData1 ((:~~:) a :: Type -> Type) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a0 -> ()) -> (a :~~: a0) -> () Source #
(NFData a1, NFData a2, NFData a3) => NFData1 ((,,,) a1 a2 a3) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> (a1, a2, a3, a) -> () Source #
(NFData1 f, NFData1 g) => NFData1 (Compose f g) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> Compose f g a -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4) => NFData1 ((,,,,) a1 a2 a3 a4) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> (a1, a2, a3, a4, a) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5) => NFData1 ((,,,,,) a1 a2 a3 a4 a5) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> (a1, a2, a3, a4, a5, a) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6) => NFData1 ((,,,,,,) a1 a2 a3 a4 a5 a6) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> (a1, a2, a3, a4, a5, a6, a) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7) => NFData1 ((,,,,,,,) a1 a2 a3 a4 a5 a6 a7) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> (a1, a2, a3, a4, a5, a6, a7, a) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7, NFData a8) => NFData1 ((,,,,,,,,) a1 a2 a3 a4 a5 a6 a7 a8) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf :: (a -> ()) -> (a1, a2, a3, a4, a5, a6, a7, a8, a) -> () Source #

rnf1 :: (NFData1 f, NFData a) => f a -> () Source #

Lift the standard rnf function through the type constructor.

Since: deepseq-1.4.3.0

For binary constructors

class (forall a. NFData a => NFData1 (p a)) => NFData2 (p :: Type -> Type -> Type) where Source #

A class of bifunctors that can be fully evaluated.

In `deepseq-1.5.0.0` this class was updated to include superclasses.

Since: deepseq-1.4.3.0

Methods

liftRnf2 :: (a -> ()) -> (b -> ()) -> p a b -> () Source #

liftRnf2 should reduce its argument to normal form (that is, fully evaluate all sub-components), given functions to reduce a and b arguments respectively, and then return ().

Note: Unlike for the unary liftRnf, there is currently no support for generically deriving liftRnf2.

Instances

Instances details

NFData2 Either Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> Either a b -> () Source #
NFData2 Arg Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> Arg a b -> () Source #
NFData2 Array Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> Array a b -> () Source #
NFData2 STRef Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> STRef a b -> () Source #
NFData2 (,) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> (a, b) -> () Source #
NFData2 (Const :: Type -> Type -> Type) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> Const a b -> () Source #
NFData2 ((:~:) :: Type -> Type -> Type) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> (a :~: b) -> () Source #
NFData a1 => NFData2 ((,,) a1) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> (a1, a, b) -> () Source #
NFData2 ((:~~:) :: Type -> Type -> Type) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> (a :~~: b) -> () Source #
(NFData a1, NFData a2) => NFData2 ((,,,) a1 a2) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> (a1, a2, a, b) -> () Source #
(NFData a1, NFData a2, NFData a3) => NFData2 ((,,,,) a1 a2 a3) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> (a1, a2, a3, a, b) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4) => NFData2 ((,,,,,) a1 a2 a3 a4) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> (a1, a2, a3, a4, a, b) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5) => NFData2 ((,,,,,,) a1 a2 a3 a4 a5) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> (a1, a2, a3, a4, a5, a, b) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6) => NFData2 ((,,,,,,,) a1 a2 a3 a4 a5 a6) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> (a1, a2, a3, a4, a5, a6, a, b) -> () Source #
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7) => NFData2 ((,,,,,,,,) a1 a2 a3 a4 a5 a6 a7) Source #	Since: deepseq-1.4.3.0
Instance details Defined in Control.DeepSeq Methods liftRnf2 :: (a -> ()) -> (b -> ()) -> (a1, a2, a3, a4, a5, a6, a7, a, b) -> () Source #

rnf2 :: (NFData2 p, NFData a, NFData b) => p a b -> () Source #

Lift the standard rnf function through the type constructor.

Since: deepseq-1.4.3.0

NFData class

Generic NFData deriving

Compatibility with previous deepseq versions

Instances

Helper functions

Examples

Instances

Liftings of the NFData class

For unary constructors

Instances

For binary constructors

Instances

`NFData` class

`Generic` `NFData` deriving

Compatibility with previous `deepseq` versions

Liftings of the `NFData` class