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).

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.

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`

operation

Redesigned `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`

operation

New `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 effect

New `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`

respectively

add `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-matching

Keep `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

`Alt`

, `Dual`

, `First`

, `Last`

, `Product`

, and `Sum`

now have `Data`

,
`MonadZip`

, and `MonadFix`

instances

The 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`

instance

Add `MonadPlus IO`

and `Alternative IO`

instances
(previously orphans in `transformers`

) (#10755)

`CallStack`

now has an `IsList`

instance

The 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.

Bundled with GHC 7.10.1

Make `Applicative`

a superclass of `Monad`

Add reverse application operator `Data.Function.(&)`

Add `Data.List.sortOn`

sorting function

Add `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`

instance

Weaken RealFloat constraints on some `Data.Complex`

functions

Add `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`

class

Add `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)

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).