# Changelog for [`base` package](http://hackage.haskell.org/package/base)
## 4.8.0.0 *TBA*
* 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`
* 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)
* 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`
* `foldr2` (together with `zip` and `zipWith`) is made a bit stricter in the
second argument, so that the fusion RULES for it do not change the
semantics. (#9596)
* `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)
## 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 is now a `Monoid`, `Generic`, and `Generic1` instance 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 `` 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).