# base

Basic libraries

Version on this page: | 4.8.0.0 |

LTS Haskell 9.20: | 4.9.1.0 |

Stackage Nightly 2017-12-18: | 4.10.1.0 |

Latest on Hackage: | 4.10.0.0 |

**libraries@haskell.org**

#### Module documentation for 4.8.0.0

There are no documented modules for this package.

This package contains the `Prelude`

and its support libraries,
and a large collection of useful libraries ranging from data
structures to parsing combinators and debugging utilities.

## Changes

# Changelog for `base`

package

## 4.10.0.0 *July 2017*

Bundled with GHC 8.2.1

`Data.Type.Bool.Not`

given a type family dependency (#12057).`Foreign.Ptr`

now exports the constructors for`IntPtr`

and`WordPtr`

(#11983)`Generic1`

, as well as the associated datatypes and typeclasses in`GHC.Generics`

, are now poly-kinded (#10604)`New modules`

Data.Bifoldable`and`

Data.Bitraversable`(previously defined in the`

bifunctors` package) (#10448)`Data.Either`

now provides`fromLeft`

and`fromRight`

(#12402)`Data.Type.Coercion`

now provides`gcoerceWith`

(#12493)New methods

`liftReadList(2)`

and`liftReadListPrec(2)`

in the`Read1`

/`Read2`

classes that are defined in terms of`ReadPrec`

instead of`ReadS`

, as well as related combinators, have been added to`Data.Functor.Classes`

(#12358)Add

`Semigroup`

instance for`IO`

, as well as for`Event`

and`Lifetime`

from`GHC.Event`

(#12464)Add

`Data`

instance for`Const`

(#12438)Added

`Eq1`

,`Ord1`

,`Read1`

and`Show1`

instances for`NonEmpty`

.Add wrappers for

`blksize_t`

,`blkcnt_t`

,`clockid_t`

,`fsblkcnt_t`

,`fsfilcnt_t`

,`id_t`

,`key_t`

, and`timer_t`

to System.Posix.Types (#12795)Add

`CBool`

, a wrapper around C's`bool`

type, to`Foreign.C.Types`

(#13136)Raw buffer operations in

`GHC.IO.FD`

are now strict in the buffer, offset, and length operations (#9696)Add

`plusForeignPtr`

to`Foreign.ForeignPtr`

.Add

`type family AppendSymbol (m :: Symbol) (n :: Symbol) :: Symbol`

to`GHC.TypeLits`

(#12162)Add

`GHC.TypeNats`

module with`Natural`

-based`KnownNat`

. The`Nat`

operations in`GHC.TypeLits`

are a thin compatibility layer on top. Note: the`KnownNat`

evidence is changed from an`Integer`

to a`Natural`

.The type of

`asProxyTypeOf`

in`Data.Proxy`

has been generalized (#12805)`liftA2`

is now a method of the`Applicative`

class.`liftA2`

and`<*>`

each have a default implementation based on the other. Various library functions have been updated to use`liftA2`

where it might offer some benefit.`liftA2`

is not yet in the`Prelude`

, and must currently be imported from`Control.Applicative`

. It is likely to be added to the`Prelude`

in the future. (#13191)A new module,

`Type.Reflection`

, exposing GHC's new type-indexed type representation mechanism is now provided.`Data.Dynamic`

now exports the`Dyn`

data constructor, enabled by the new type-indexed type representation mechanism.`Data.Type.Equality`

now provides a kind heterogeneous type equality evidence type,`(:~~:)`

.The

`CostCentresXML`

constructor of`GHC.RTS.Flags.DoCostCentres`

has been replaced by`CostCentresJSON`

due to the new JSON export format supported by the cost centre profiler.The

`ErrorCall`

pattern synonym has been given a`COMPLETE`

pragma so that functions which solely match again`ErrorCall`

do not produce non-exhaustive pattern-match warnings (#8779)Change the implementations of

`maximumBy`

and`minimumBy`

from`Data.Foldable`

to use`foldl1`

instead of`foldr1`

. This makes them run in constant space when applied to lists. (#10830)`mkFunTy`

,`mkAppTy`

, and`mkTyConApp`

from`Data.Typeable`

no longer exist. This functionality is superceded by the interfaces provided by`Type.Reflection`

.`mkTyCon3`

is no longer exported by`Data.Typeable`

. This function is replaced by`Type.Reflection.Unsafe.mkTyCon`

.`Data.List.NonEmpty.unfold`

has been deprecated in favor of`unfoldr`

, which is functionally equivalent.

## 4.9.0.0 *May 2016*

Bundled with GHC 8.0

`error`

and`undefined`

now print a partial stack-trace alongside the error message.New

`errorWithoutStackTrace`

function throws an error without printing the stack trace.The restore operation provided by

`mask`

and`uninterruptibleMask`

now restores the previous masking state whatever the current masking state is.New

`GHC.Generics.packageName`

operationRedesigned

`GHC.Stack.CallStack`

data type. As a result,`CallStack`

's`Show`

instance produces different output, and`CallStack`

no longer has an`Eq`

instance.New

`GHC.Generics.packageName`

operationNew

`GHC.Stack.Types`

module now contains the definition of`CallStack`

and`SrcLoc`

New

`GHC.Stack.Types.emptyCallStack`

function builds an empty`CallStack`

New

`GHC.Stack.Types.freezeCallStack`

function freezes a`CallStack`

preventing future`pushCallStack`

operations from having any effectNew

`GHC.Stack.Types.pushCallStack`

function pushes a call-site onto a`CallStack`

New

`GHC.Stack.Types.fromCallSiteList`

function creates a`CallStack`

from a list of call-sites (i.e.,`[(String, SrcLoc)]`

)`GHC.SrcLoc`

has been removed`GHC.Stack.showCallStack`

and`GHC.SrcLoc.showSrcLoc`

are now called`GHC.Stack.prettyCallStack`

and`GHC.Stack.prettySrcLoc`

respectivelyadd

`Data.List.NonEmpty`

and`Data.Semigroup`

(to become super-class of`Monoid`

in the future). These modules were provided by the`semigroups`

package previously. (#10365)Add

`selSourceUnpackedness`

,`selSourceStrictness`

, and`selDecidedStrictness`

, three functions which look up strictness information of a field in a data constructor, to the`Selector`

type class in`GHC.Generics`

(#10716)Add

`URec`

,`UAddr`

,`UChar`

,`UDouble`

,`UFloat`

,`UInt`

, and`UWord`

to`GHC.Generics`

as part of making GHC generics capable of handling unlifted types (#10868)The

`Eq`

,`Ord`

,`Read`

, and`Show`

instances for`U1`

now use lazier pattern-matchingKeep

`shift{L,R}`

on`Integer`

with negative shift-arguments from segfaulting (#10571)Add

`forkOSWithUnmask`

to`Control.Concurrent`

, which is like`forkIOWithUnmask`

, but the child is run in a bound thread.The

`MINIMAL`

definition of`Arrow`

is now`arr AND (first OR (***))`

.The

`MINIMAL`

definition of`ArrowChoice`

is now`left OR (+++)`

.Exported

`GiveGCStats`

,`DoCostCentres`

,`DoHeapProfile`

,`DoTrace`

,`RtsTime`

, and`RtsNat`

from`GHC.RTS.Flags`

New function

`GHC.IO.interruptible`

used to correctly implement`Control.Exception.allowInterrupt`

(#9516)Made

`PatternMatchFail`

,`RecSelError`

,`RecConError`

,`RecUpdError`

,`NoMethodError`

, and`AssertionFailed`

newtypes (#10738)New module

`Control.Monad.IO.Class`

(previously provided by`transformers`

package). (#10773)New modules

`Data.Functor.Classes`

,`Data.Functor.Compose`

,`Data.Functor.Product`

, and`Data.Functor.Sum`

(previously provided by`transformers`

package). (#11135)New instances for

`Proxy`

:`Eq1`

,`Ord1`

,`Show1`

,`Read1`

. All of the classes are from`Data.Functor.Classes`

(#11756).New module

`Control.Monad.Fail`

providing new`MonadFail(fail)`

class (#10751)Add

`GHC.TypeLits.TypeError`

and`ErrorMessage`

to allow users to define custom compile-time error messages.Redesign

`GHC.Generics`

to use type-level literals to represent the metadata of generic representation types (#9766)The

`IsString`

instance for`[Char]`

has been modified to eliminate ambiguity arising from overloaded strings and functions like`(++)`

.Move

`Const`

from`Control.Applicative`

to its own module in

`Data.Functor.Const`

. (#11135)

Re-export

`Const`

from`Control.Applicative`

for backwards compatibility.Expand

`Floating`

class to include operations that allow for better precision:`log1p`

,`expm1`

,`log1pexp`

and`log1mexp`

. These are not available from`Prelude`

, but the full class is exported from`Numeric`

.New

`Control.Exception.TypeError`

datatype, which is thrown when an expression fails to typecheck when run using`-fdefer-type-errors`

(#10284)

### New instances

`Alt`

,`Dual`

,`First`

,`Last`

,`Product`

, and`Sum`

now have`Data`

,`MonadZip`

, and`MonadFix`

instancesThe datatypes in

`GHC.Generics`

now have`Enum`

,`Bounded`

,`Ix`

,`Functor`

,`Applicative`

,`Monad`

,`MonadFix`

,`MonadPlus`

,`MonadZip`

,`Foldable`

,`Foldable`

,`Traversable`

,`Generic1`

, and`Data`

instances as appropriate.`Maybe`

now has a`MonadZip`

instance`All`

and`Any`

now have`Data`

instances`Dual`

,`First`

,`Last`

,`Product`

, and`Sum`

now have`Foldable`

and`Traversable`

instances`Dual`

,`Product`

, and`Sum`

now have`Functor`

,`Applicative`

, and`Monad`

instances`(,) a`

now has a`Monad`

instance`ZipList`

now has`Foldable`

and`Traversable`

instances`Identity`

now has`Semigroup`

and`Monoid`

instances`Identity`

and`Const`

now have`Bits`

,`Bounded`

,`Enum`

,`FiniteBits`

,`Floating`

,`Fractional`

,`Integral`

,`IsString`

,`Ix`

,`Num`

,`Real`

,`RealFloat`

,`RealFrac`

and`Storable`

instances. (#11210, #11790)`()`

now has a`Storable`

instance`Complex`

now has`Generic`

,`Generic1`

,`Functor`

,`Foldable`

,`Traversable`

,`Applicative`

, and`Monad`

instances`System.Exit.ExitCode`

now has a`Generic`

instance`Data.Version.Version`

now has a`Generic`

instance`IO`

now has a`Monoid`

instanceAdd

`MonadPlus IO`

and`Alternative IO`

instances (previously orphans in`transformers`

) (#10755)`CallStack`

now has an`IsList`

instanceThe field

`spInfoName`

of`GHC.StaticPtr.StaticPtrInfo`

has been removed. The value is no longer available when constructing the`StaticPtr`

.`VecElem`

and`VecCount`

now have`Enum`

and`Bounded`

instances.

### Generalizations

Generalize

`Debug.Trace.{traceM, traceShowM}`

from`Monad`

to`Applicative`

(#10023)- Redundant typeclass constraints have been removed:
`Data.Ratio.{denominator,numerator}`

have no`Integral`

constraint anymore**TODO**

Generalise

`forever`

from`Monad`

to`Applicative`

Generalize

`filterM`

,`mapAndUnzipM`

,`zipWithM`

,`zipWithM_`

,`replicateM`

,`replicateM_`

from`Monad`

to`Applicative`

(#10168)The

`Generic`

instance for`Proxy`

is now poly-kinded (#10775)Enable

`PolyKinds`

in the`Data.Functor.Const`

module to give`Const`

the kind`* -> k -> *`

. (#10039)

## 4.8.2.0 *Oct 2015*

Bundled with GHC 7.10.3

The restore operation provided by

`mask`

and`uninterruptibleMask`

now restores the previous masking state whatever the current masking state is.Exported

`GiveGCStats`

,`DoCostCentres`

,`DoHeapProfile`

,`DoTrace`

,`RtsTime`

, and`RtsNat`

from`GHC.RTS.Flags`

## 4.8.1.0 *Jul 2015*

Bundled with GHC 7.10.2

`Lifetime`

is now exported from`GHC.Event`

Implicit-parameter based source location support exposed in

`GHC.SrcLoc`

and`GHC.Stack`

. See GHC User's Manual for more information.

## 4.8.0.0 *Mar 2015*

Bundled with GHC 7.10.1

Make

`Applicative`

a superclass of`Monad`

Add reverse application operator

`Data.Function.(&)`

Add

`Data.List.sortOn`

sorting functionAdd

`System.Exit.die`

Deprecate

`versionTags`

field of`Data.Version.Version`

. Add`makeVersion :: [Int] -> Version`

constructor function to aid migration to a future`versionTags`

-less`Version`

.Add

`IsList Version`

instanceWeaken RealFloat constraints on some

`Data.Complex`

functionsAdd

`Control.Monad.(<$!>)`

as a strict version of`(<$>)`

The

`Data.Monoid`

module now has the`PolyKinds`

extension enabled, so that the`Monoid`

instance for`Proxy`

are polykinded like`Proxy`

itself is.Make

`abs`

and`signum`

handle (-0.0) correctly per IEEE-754.Re-export

`Data.Word.Word`

from`Prelude`

Add

`countLeadingZeros`

and`countTrailingZeros`

methods to`Data.Bits.FiniteBits`

classAdd

`Data.List.uncons`

list destructor (#9550)Export

`Monoid(..)`

from`Prelude`

Export

`Foldable(..)`

from`Prelude`

(hiding`fold`

,`foldl'`

,`foldr'`

, and`toList`

)Export

`Traversable(..)`

from`Prelude`

Set fixity for

`Data.Foldable.{elem,notElem}`

to match the conventional one set for`Data.List.{elem,notElem}`

(#9610)Turn

`toList`

,`elem`

,`sum`

,`product`

,`maximum`

, and`minimum`

into`Foldable`

methods (#9621)Replace the

`Data.List`

-exported functions`all, and, any, concat, concatMap, elem, find, product, sum, mapAccumL, mapAccumR`

by re-exports of their generalised

`Data.Foldable`

/`Data.Traversable`

counterparts. In other words, unqualified imports of`Data.List`

and`Data.Foldable`

/`Data.Traversable`

no longer lead to conflicting definitions. (#9586)New (unofficial) module

`GHC.OldList`

containing only list-specialised versions of the functions from`Data.List`

(in other words,`GHC.OldList`

corresponds to`base-4.7.0.2`

's`Data.List`

)Replace the

`Control.Monad`

-exported functions`sequence_, msum, mapM_, forM_, forM, mapM, sequence`

by re-exports of their generalised

`Data.Foldable`

/`Data.Traversable`

counterparts. In other words, unqualified imports of`Control.Monad`

and`Data.Foldable`

/`Data.Traversable`

no longer lead to conflicting definitions. (#9586)Generalise

`Control.Monad.{when,unless,guard}`

from`Monad`

to`Applicative`

and from`MonadPlus`

to`Alternative`

respectively.Generalise

`Control.Monad.{foldM,foldM_}`

to`Foldable`

`scanr`

,`mapAccumL`

and`filterM`

now take part in list fusion (#9355, #9502, #9546)Remove deprecated

`Data.OldTypeable`

(#9639)New module

`Data.Bifunctor`

providing the`Bifunctor(bimap,first,second)`

class (previously defined in`bifunctors`

package) (#9682)New module

`Data.Void`

providing the canonical uninhabited type`Void`

(previously defined in`void`

package) (#9814)Update Unicode class definitions to Unicode version 7.0

Add

`Alt`

, an`Alternative`

wrapper, to`Data.Monoid`

. (#9759)Add

`isSubsequenceOf`

to`Data.List`

(#9767)The arguments to

`==`

and`eq`

in`Data.List.nub`

and`Data.List.nubBy`

are swapped, such that`Data.List.nubBy (<) [1,2]`

now returns`[1]`

instead of`[1,2]`

(#2528, #3280, #7913)New module

`Data.Functor.Identity`

(previously provided by`transformers`

package). (#9664)Add

`scanl'`

, a strictly accumulating version of`scanl`

, to`Data.List`

and`Data.OldList`

. (#9368)Add

`fillBytes`

to`Foreign.Marshal.Utils`

.Add new

`displayException`

method to`Exception`

typeclass. (#9822)Add

`Data.Bits.toIntegralSized`

, a size-checked version of`fromIntegral`

. (#9816)New module

`Numeric.Natural`

providing new`Natural`

type representing non-negative arbitrary-precision integers. The`GHC.Natural`

module exposes additional GHC-specific primitives. (#9818)Add

`(Storable a, Integeral a) => Storable (Ratio a)`

instance (#9826)Add

`Storable a => Storable (Complex a)`

instance (#9826)New module

`GHC.RTS.Flags`

that provides accessors to runtime flags.Expose functions for per-thread allocation counters and limits in

`GHC.Conc`

`disableAllocationLimit :: IO () enableAllocationLimit :: IO () getAllocationCounter :: IO Int64 setAllocationCounter :: Int64 -> IO ()`

together with a new exception

`AllocationLimitExceeded`

.Make

`read . show = id`

for`Data.Fixed`

(#9240)Add

`calloc`

and`callocBytes`

to`Foreign.Marshal.Alloc`

. (#9859)Add

`callocArray`

and`callocArray0`

to`Foreign.Marshal.Array`

. (#9859)Restore invariant in

`Data (Ratio a)`

instance (#10011)Add/expose

`rnfTypeRep`

,`rnfTyCon`

,`typeRepFingerprint`

, and`tyConFingerprint`

helpers to`Data.Typeable`

.Define proper

`MINIMAL`

pragma for`class Ix`

. (#10142)

## 4.7.0.2 *Dec 2014*

Bundled with GHC 7.8.4

Fix performance bug in

`Data.List.inits`

(#9345)Fix handling of null bytes in

`Debug.Trace.trace`

(#9395)

## 4.7.0.1 *Jul 2014*

Bundled with GHC 7.8.3

Unhide

`Foreign.ForeignPtr`

in Haddock (#8475)Fix recomputation of

`TypeRep`

in`Typeable`

type-application instance (#9203)Fix regression in Data.Fixed Read instance (#9231)

Fix

`fdReady`

to honor`FD_SETSIZE`

(#9168)

## 4.7.0.0 *Apr 2014*

Bundled with GHC 7.8.1

Add

`/Since: 4.[4567].0.0/`

Haddock annotations to entities denoting the package version, when the given entity was introduced (or its type signature changed in a non-compatible way)The

`Control.Category`

module now has the`PolyKinds`

extension enabled, meaning that instances of`Category`

no longer need be of kind`* -> * -> *`

.There are now

`Foldable`

and`Traversable`

instances for`Either a`

,

`Const r`

, and `(,) a`

.

There are now

`Show`

,`Read`

,`Eq`

,`Ord`

,`Monoid`

,`Generic`

, and`Generic1`

instances for`Const`

.There is now a

`Data`

instance for`Data.Version`

.A new

`Data.Bits.FiniteBits`

class has been added to represent types with fixed bit-count. The existing`Bits`

class is extended with a`bitSizeMaybe`

method to replace the now obsolete`bitsize`

method.`Data.Bits.Bits`

gained a new`zeroBits`

method which completes the`Bits`

API with a direct way to introduce a value with all bits cleared.There are now

`Bits`

and`FiniteBits`

instances for`Bool`

.There are now

`Eq`

,`Ord`

,`Show`

,`Read`

,`Generic`

. and`Generic1`

instances for`ZipList`

.There are now

`Eq`

,`Ord`

,`Show`

and`Read`

instances for`Down`

.There are now

`Eq`

,`Ord`

,`Show`

,`Read`

and`Generic`

instances for types in GHC.Generics (`U1`

,`Par1`

,`Rec1`

,`K1`

,`M1`

,`(:+:)`

,`(:*:)`

,`(:.:)`

).`Data.Monoid`

: There are now`Generic`

instances for`Dual`

,`Endo`

,`All`

,`Any`

,`Sum`

,`Product`

,`First`

, and`Last`

; as well as`Generic1`

instances for`Dual`

,`Sum`

,`Product`

,`First`

, and`Last`

.The

`Data.Monoid.{Product,Sum}`

newtype wrappers now have`Num`

instances.There are now

`Functor`

instances for`System.Console.GetOpt`

's`ArgOrder`

,`OptDescr`

, and`ArgDescr`

.A zero-width unboxed poly-kinded

`Proxy#`

was added to`GHC.Prim`

. It can be used to make it so that there is no the operational overhead for passing around proxy arguments to model type application.New

`Data.Proxy`

module providing a concrete, poly-kinded proxy type.New

`Data.Coerce`

module which exports the new`Coercible`

class together with the`coerce`

primitive which provide safe coercion (wrt role checking) between types with same representation.`Control.Concurrent.MVar`

has a new implementation of`readMVar`

, which fixes a long-standing bug where`readMVar`

is only atomic if there are no other threads running`putMVar`

.`readMVar`

now is atomic, and is guaranteed to return the value from the first`putMVar`

. There is also a new`tryReadMVar`

which is a non-blocking version.New

`Control.Concurrent.MVar.withMVarMasked`

which executes`IO`

action with asynchronous exceptions masked in the same style as the existing`modifyMVarMasked`

and`modifyMVarMasked_`

.New

`threadWait{Read,Write}STM :: Fd -> IO (STM (), IO ())`

functions added to`Control.Concurrent`

for waiting on FD readiness with STM actions.Expose

`Data.Fixed.Fixed`

's constructor.There are now byte endian-swapping primitives

`byteSwap{16,32,64}`

available in`Data.Word`

, which use optimized machine instructions when available.`Data.Bool`

now exports`bool :: a -> a -> Bool -> a`

, analogously to`maybe`

and`either`

in their respective modules.`Data.Either`

now exports`isLeft, isRight :: Either a b -> Bool`

.`Debug.Trace`

now exports`traceId`

,`traceShowId`

,`traceM`

, and`traceShowM`

.`Data.Functor`

now exports`($>)`

and`void`

.Rewrote portions of

`Text.Printf`

, and made changes to`Numeric`

(added`Numeric.showFFloatAlt`

and`Numeric.showGFloatAlt`

) and`GHC.Float`

(added`formatRealFloatAlt`

) to support it. The rewritten version is extensible to user types, adds a "generic" format specifier "`%v`

", extends the`printf`

spec to support much of C's`printf(3)`

functionality, and fixes the spurious warnings about using`Text.Printf.printf`

at`(IO a)`

while ignoring the return value. These changes were contributed by Bart Massey.The minimal complete definitions for all type-classes with cyclic default implementations have been explicitly annotated with the new

`{-# MINIMAL #-}`

pragma.`Control.Applicative.WrappedMonad`

, which can be used to convert a`Monad`

to an`Applicative`

, has now a`Monad m => Monad (WrappedMonad m)`

instance.There is now a

`Generic`

and a`Generic1`

instance for`WrappedMonad`

and`WrappedArrow`

.Handle

`ExitFailure (-sig)`

on Unix by killing process with signal`sig`

.New module

`Data.Type.Bool`

providing operations on type-level booleans.Expose

`System.Mem.performMinorGC`

for triggering minor GCs.New

`System.Environment.{set,unset}Env`

for manipulating environment variables.Add

`Typeable`

instance for`(->)`

and`RealWorld`

.Declare CPP header

`<Typeable.h>`

officially obsolete as GHC 7.8+ does not support hand-written`Typeable`

instances anymore.Remove (unmaintained) Hugs98 and NHC98 specific code.

Optimize

`System.Timeout.timeout`

for the threaded RTS.Remove deprecated functions

`unsafeInterleaveST`

,`unsafeIOToST`

, and`unsafeSTToIO`

from`Control.Monad.ST`

.Add a new superclass

`SomeAsyncException`

for all asynchronous exceptions and makes the existing`AsyncException`

and`Timeout`

exception children of`SomeAsyncException`

in the hierarchy.Remove deprecated functions

`blocked`

,`unblock`

, and`block`

from`Control.Exception`

.Remove deprecated function

`forkIOUnmasked`

from`Control.Concurrent`

.Remove deprecated function

`unsafePerformIO`

export from`Foreign`

(still available via`System.IO.Unsafe.unsafePerformIO`

).Various fixes and other improvements (see Git history for full details).

**and many more**