# base

Basic libraries

Version on this page: | 4.8.1.0 |

LTS Haskell 11.5: | 4.10.1.0 |

Stackage Nightly 2018-04-20: | 4.11.0.0 |

Latest on Hackage: | 4.11.0.0 |

**libraries@haskell.org**

#### Module documentation for 4.8.1.0

- Control
- Data
- Data.Bifunctor
- Data.Bits
- Data.Bool
- Data.Char
- Data.Coerce
- Data.Complex
- Data.Data
- Data.Dynamic
- Data.Either
- Data.Eq
- Data.Fixed
- Data.Foldable
- Data.Function
- Data.Functor
- Data.IORef
- Data.Int
- Data.Ix
- Data.List
- Data.Maybe
- Data.Monoid
- Data.Ord
- Data.Proxy
- Data.Ratio
- Data.STRef
- Data.String
- Data.Traversable
- Data.Tuple
- Data.Type
- Data.Typeable
- Data.Unique
- Data.Version
- Data.Void
- Data.Word

- Debug
- Foreign
- GHC
- Numeric
- Prelude
- System
- Text
- Unsafe

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

## 4.11.0.0 *TBA*

Bundled with GHC 8.4.1

`System.IO.openTempFile`

is now thread-safe on Windows.Deprecated

`GHC.Stats.GCStats`

interface has been removed.Add

`showHFloat`

to`Numeric`

Add

`Div`

,`Mod`

, and`Log2`

functions on type-level naturals in`GHC.TypeLits`

.Add

`Alternative`

instance for`ZipList`

(#13520)Add instances

`Num`

,`Functor`

,`Applicative`

,`Monad`

,`Semigroup`

and`Monoid`

for`Data.Ord.Down`

(#13097).Add

`Semigroup`

instance for`EventLifetime`

.Make

`Semigroup`

a superclass of`Monoid`

; export`Semigroup((<>))`

from`Prelude`

; remove`Monoid`

reexport from`Data.Semigroup`

(#14191).Generalise

`instance Monoid a => Monoid (Maybe a)`

to`instance Semigroup a => Monoid (Maybe a)`

.Add

`infixl 9 !!`

declaration for`Data.List.NonEmpty.!!`

Add

`<&>`

operator to`Data.Functor`

(#14029)Remove the deprecated

`Typeable{1..7}`

type synonyms (#14047)Make

`Data.Type.Equality.==`

a closed type family. It now works for all

kinds out of the box. Any modules that previously declared instances of this
family will need to remove them. Whereas the previous definition was somewhat
ad hoc, the behavior is now completely uniform. As a result, some applications
that used to reduce no longer do, and conversely. Most notably, `(==)`

no
longer treats the `*`

, `j -> k`

, or `()`

kinds specially; equality is
tested structurally in all cases.

Add instances

`Semigroup`

and`Monoid`

for`Control.Monad.ST`

(#14107).The

`Read`

instances for`Proxy`

,`Coercion`

,`(:~:)`

,`(:~~:)`

, and`U1`

now ignore the parsing precedence. The effect of this is that`read`

will be able to successfully parse more strings containing`"Proxy"`

*et al.*without surrounding parentheses (e.g.,`"Thing Proxy"`

) (#12874).Add

`iterate'`

, a strict version of`iterate`

, to`Data.List`

and`Data.OldList`

(#3474)Add

`Data`

instances for`IntPtr`

and`WordPtr`

(#13115)Add missing

`MonadFail`

instance for`Control.Monad.Strict.ST.ST`

Make

`zipWith`

and`zipWith3`

inlinable (#14224)`Type.Reflection.App`

now matches on function types (fixes #14236)`Type.Reflection.withTypeable`

is now polymorphic in the`RuntimeRep`

of its result.Add

`installSEHHandlers`

to`MiscFlags`

in`GHC.RTS.Flags`

to determine if exception handling is enabled.The deprecated functions

`isEmptyChan`

and`unGetChan`

in`Control.Concurrent.Chan`

have been removed (#13561).Add

`generateCrashDumpFile`

to`MiscFlags`

in`GHC.RTS.Flags`

to determine if a core dump will be generated on crashes.Add

`generateStackTrace`

to`MiscFlags`

in`GHC.RTS.Flags`

to determine if stack traces will be generated on unhandled exceptions by the RTS.`getExecutablePath`

now resolves symlinks on Windows (#14483)Deprecated STM invariant checking primitives (

`checkInv`

,`always`

, and`alwaysSucceeds`

) in`GHC.Conc.Sync`

(#14324).

## 4.10.1.0 *November 2017*

Bundled with GHC 8.2.2

The file locking primitives provided by

`GHC.IO.Handle`

now use Linux open file descriptor locking if available.Fixed bottoming definition of

`clearBit`

for`Natural`

## 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**