Changelog for base package

4.19.2.0 October 2024

• Shipped with GHC 9.8.3
• Improve documentation of various functions
• Fix interaction between fork and the kqueue-based IO manager (#24672)

4.19.1.0 October 2023

• Shipped with GHC 9.8.2
• Improve documentation of various functions
• Implement primitives like lstat and rmdir, for the JS backend.

4.19.0.0 October 2023

• Shipped with GHC 9.8.1
• Add {-# WARNING in "x-partial" #-} to Data.List.{head,tail}. Use {-# OPTIONS_GHC -Wno-x-partial #-} to disable it. (CLC proposal #87 and #114)
• GHC.Conc.Sync now exports fromThreadId :: ThreadId -> Word64, which maps a thread to a per-process-unique identifier (CLC proposal #117)
• Add Data.List.!? (CLC proposal #110)
• maximumBy/minimumBy are now marked as INLINE improving performance for unpackable types significantly.
• Add INLINABLE pragmas to generic* functions in Data.OldList (CLC proposal #129)
• Export getSolo from Data.Tuple. (CLC proposal #113)
• Add Type.Reflection.decTypeRep, Data.Typeable.decT and Data.Typeable.hdecT equality decisions functions. (CLC proposal #98)
• Add Data.Functor.unzip (CLC proposal #88)
• Add System.Mem.Weak.{get,set}FinalizerExceptionHandler, which allows the user to set the global handler invoked by when a Weak pointer finalizer throws an exception. (CLC proposal #126)
• Add System.Mem.Weak.printToHandleFinalizerExceptionHandler, which can be used with setFinalizerExceptionHandler to print exceptions thrown by finalizers to the given Handle. (CLC proposal #126)
• Add Data.List.unsnoc (CLC proposal #165)
• Implement more members of instance Foldable (Compose f g) explicitly. (CLC proposal #57)
• Add Eq and Ord instances for SSymbol, SChar, and SNat. (CLC proposal #148)
• Add COMPLETE pragmas to the TypeRep, SSymbol, SChar, and SNat pattern synonyms. (CLC proposal #149)
• Make ($) representation polymorphic (CLC proposal #132)
• Make (&) representation polymorphic in the return type (CLC proposal #158)
• Implemented GHC Proposal #433, adding the class Unsatisfiable :: ErrorMessage -> TypeError to GHC.TypeError, which provides a mechanism for custom type errors that reports the errors in a more predictable behaviour than TypeError.
• Add more instances for Compose: Enum, Bounded, Num, Real, Integral (CLC proposal #160)
• Implement GHC.IORef.atomicSwapIORef via a new dedicated primop atomicSwapMutVar# (CLC proposal #139)
• Change codebuffers to use an unboxed implementation, while providing a compatibility layer using pattern synonyms. (CLC proposal #134)
• Add nominal role annotations to SNat/SSymbol/SChar (CLC proposal #170)
• Update to Unicode 15.1.0.
• Make Semigroup’s stimes specializable. (CLC proposal #8)
• Deprecate Data.List.NonEmpty.unzip (CLC proposal #86)
• Fixed exponent overflow/underflow bugs in the Read instances for Float and Double (CLC proposal #192)
• Implement copyBytes, fillBytes, moveBytes and stimes for Data.Array.Byte.ByteArray using primops (CLC proposal #188)
• Add rewrite rules for conversion between Int64 / Word64 and Float / Double on 64-bit architectures (CLC proposal #203).
• Generic instances for tuples now expose Unit, Tuple2, Tuple3, …, Tuple64 as the actual names for tuple type constructors (GHC proposal #475).

4.18.0.0 March 2023

• Shipped with GHC 9.6.1
• Foreign.C.ConstPtr.ConstrPtr was added to encode const-qualified pointer types in foreign declarations when using CApiFFI extension. (CLC proposal #117)
• Add forall a. Functor (p a) superclass for Bifunctor p (CLC proposal #91)
• Add forall a. Functor (p a) superclass for Bifunctor p.
• Add Functor instances for (,,,,) a b c d, (,,,,,) a b c d e and (,,,,,) a b c d e f.
• Exceptions thrown by weak pointer finalizers can now be reported by setting a global exception handler, using System.Mem.Weak.setFinalizerExceptionHandler. The default behaviour is unchanged (exceptions are ignored and not reported).
• Numeric.Natural re-exports GHC.Natural.minusNaturalMaybe (CLC proposal #45)
• Add Data.Foldable1 and Data.Bifoldable1 (CLC proposal #9)
• Add applyWhen to Data.Function (CLC proposal #71)
• Add functions mapAccumM and forAccumM to Data.Traversable (CLC proposal #65)
• Add default implementation of (<>) in terms of sconcat and mempty in terms of mconcat (CLC proposal #61).
• GHC.Conc.Sync.listThreads was added, allowing the user to list the threads (both running and blocked) of the program.
• GHC.Conc.Sync.labelThreadByteArray# was added, allowing the user to specify a thread label by way of a ByteArray# containing a UTF-8-encoded string. The old GHC.Conc.Sync.labelThread is now implemented in terms of this function.
• GHC.Conc.Sync.threadLabel was added, allowing the user to query the label of a given ThreadId.
• Add inits1 and tails1 to Data.List.NonEmpty (CLC proposal #67)
• Change default Ord implementation of (>=), (>), and (<) to use (<=) instead of compare (CLC proposal #24).
• Export liftA2 from Prelude. This means that the entirety of Applicative is now exported from Prelude (CLC proposal #50, the migration guide)
• Switch to a pure Haskell implementation of GHC.Unicode (CLC proposals #59 and #130)
• Update to Unicode 15.0.0.
• Add standard Unicode case predicates isUpperCase and isLowerCase to GHC.Unicode and Data.Char. These predicates use the standard Unicode case properties and are more intuitive than isUpper and isLower (CLC proposal #90)
• Add Eq and Ord instances for Generically1.
• Relax instances for Functor combinators; put superclass on Class1 and Class2 to make non-breaking (CLC proposal #10, migration guide)
• Add gcdetails_block_fragmentation_bytes to GHC.Stats.GCDetails to track heap fragmentation.
• GHC.TypeLits and GHC.TypeNats now export the natSing, symbolSing, and charSing methods of KnownNat, KnownSymbol, and KnownChar, respectively. They also export the SNat, SSymbol, and SChar types that are used in these methods and provide an API to interact with these types, per CLC proposal #85.
• The Enum instance of Down a now enumerates values in the opposite order as the Enum a instance (CLC proposal #51)
• Foreign.Marshal.Pool now uses the RTS internal arena instead of libc malloc for allocation. It avoids the O(n) overhead of maintaining a list of individually allocated pointers as well as freeing each one of them when freeing a Pool (#14762, #18338)
• Type.Reflection.Unsafe is now marked as unsafe.
• Add Data.Typeable.heqT, a kind-heterogeneous version of Data.Typeable.eqT (CLC proposal #99)
• Various declarations GHC’s new info-table provenance feature have been moved from GHC.Stack.CCS to a new GHC.InfoProv module:
  • The InfoProv, along its ipName, ipDesc, ipTyDesc, ipLabel, ipMod, and ipLoc fields, have been moved.
  • InfoProv now has additional ipSrcFile and ipSrcSpan fields. ipLoc is now a function computed from these fields.
  • The whereFrom function has been moved
• Add functions traceWith, traceShowWith, traceEventWith to Debug.Trace, per CLC proposal #36.
• Export List from GHC.List (CLC proposal #186).

4.17.0.0 August 2022

• Shipped with GHC 9.4.1

• Add explicitly bidirectional pattern TypeRep to Type.Reflection.

• Add Generically and Generically1 to GHC.Generics for deriving generic instances with DerivingVia. Generically instances include Semigroup and Monoid. Generically1 instances: Functor, Applicative, Alternative, Eq1 and Ord1.

• Introduce GHC.ExecutablePath.executablePath, which is more robust than getExecutablePath in cases when the executable has been deleted.

• Add Data.Array.Byte module, providing boxed ByteArray# and MutableByteArray# wrappers.

• fromEnum for Natural now throws an error for any number that cannot be repesented exactly by an Int (#20291).

• returnA is defined as Control.Category.id instead of arr id.

• Added symbolic synonyms for xor and shift operators to Data.Bits:

  • .^. (xor),
  • .>>. and !>>. (shiftR and unsafeShiftR),
  • .<<. and !<<. (shiftL and unsafeShiftL).

  These new operators have the same fixity as the originals.

• GHC.Exts now re-exports Multiplicity and MultMul.

• A large number of partial functions in Data.List and Data.List.NonEmpty now have an HasCallStack constraint. Hopefully providing better error messages in case they are used in unexpected ways.

• Fix the Ord1 instance for Data.Ord.Down to reverse sort order.

• Any Haskell type that wraps a C pointer type has been changed from Ptr () to CUIntPtr. For typical glibc based platforms, the affected type is CTimer.

• Remove instances of MonadFail for the ST monad (lazy and strict) as per the Core Libraries proposal. A migration guide is available.

• Re-export augment and build function from GHC.List

• Re-export the IsList typeclass from the new GHC.IsList module.

• There’s a new special function withDict in GHC.Exts: ::

  withDict :: forall {rr :: RuntimeRep} cls meth (r :: TYPE rr). WithDict cls meth => meth -> (cls => r) -> r
  

  where cls must be a class containing exactly one method, whose type must be meth.

  This function converts meth to a type class dictionary. It removes the need for unsafeCoerce in implementation of reflection libraries. It should be used with care, because it can introduce incoherent instances.

  For example, the withTypeable function from the Type.Reflection module can now be defined as: ::

    withTypeable :: forall k (a :: k) rep (r :: TYPE rep). ()
                 => TypeRep a -> (Typeable a => r) -> r
    withTypeable rep k = withDict @(Typeable a) rep k
  

  Note that the explicit type application is required, as the call to withDict would be ambiguous otherwise.

  This replaces the old GHC.Exts.magicDict, which required an intermediate data type and was less reliable.

• Data.Word.Word64 and Data.Int.Int64 are now always represented by Word64# and Int64#, respectively. Previously on 32-bit platforms these were rather represented by Word# and Int#. See GHC #11953.

• Add GHC.TypeError module to contain functionality related to custom type errors. TypeError is re-exported from GHC.TypeLits for backwards compatibility.

• Comparison constraints in Data.Type.Ord (e.g. <=) now use the new GHC.TypeError.Assert type family instead of type equality with ~.

4.16.3.0 May 2022

• Shipped with GHC 9.2.4

• winio: make consoleReadNonBlocking not wait for any events at all.

• winio: Add support to console handles to handleToHANDLE

4.16.2.0 May 2022

• Shipped with GHC 9.2.2

• Export GHC.Event.Internal on Windows (#21245)

Documentation Fixes

4.16.1.0 Feb 2022

• Shipped with GHC 9.2.2

• The following Foreign C types now have an instance of Ix: CChar, CSChar, CUChar, CShort, CUShort, CInt, CUInt, CLong, CULong, CPtrdiff, CSize, CWchar, CSigAtomic, CLLong, CULLong, CBool, CIntPtr, CUIntPtr, CIntMax, CUIntMax.

4.16.0.0 Nov 2021

• Shipped with GHC 9.2.1

• The unary tuple type, Solo, is now exported by Data.Tuple.

• Add a Typeable constraint to fromStaticPtr in the class GHC.StaticPtr.IsStatic.

• Make it possible to promote Naturals and remove the separate Nat kind. For backwards compatibility, Nat is now a type synonym for Natural. As a consequence, one must enable TypeSynonymInstances in order to define instances for Nat. Also, different instances for Nat and Natural won’t typecheck anymore.

• Add Data.Type.Ord as a module for type-level comparison operations. The (<=?) type operator from GHC.TypeNats, previously kind-specific to Nat, is now kind-polymorphic and governed by the Compare type family in Data.Type.Ord. Note that this means GHC will no longer deduce 0 <= n for all n any more.

• Add cmpNat, cmpSymbol, and cmpChar to GHC.TypeNats and GHC.TypeLits.

• Add CmpChar, ConsSymbol, UnconsSymbol, CharToNat, and NatToChar type families to GHC.TypeLits.

• Add the KnownChar class, charVal and charVal' to GHC.TypeLits.

• Add Semigroup and Monoid instances for Data.Functor.Product and Data.Functor.Compose.

• Add Functor, Applicative, Monad, MonadFix, Foldable, Traversable, Eq, Ord, Show, Read, Eq1, Ord1, Show1, Read1, Generic, Generic1, and Data instances for GHC.Tuple.Solo.

• Add Eq1, Read1 and Show1 instances for Complex; add Eq1/2, Ord1/2, Show1/2 and Read1/2 instances for 3 and 4-tuples.

• Remove Data.Semigroup.Option and the accompanying option function.

• Make allocaBytesAligned and alloca throw an IOError when the alignment is not a power-of-two. The underlying primop newAlignedPinnedByteArray# actually always assumed this but we didn’t document this fact in the user facing API until now.

  Generic1, and Data instances for GHC.Tuple.Solo.

• Under POSIX, System.IO.openFile will no longer leak a file descriptor if it is interrupted by an asynchronous exception (#19114, #19115).

• Additionally export asum from Control.Applicative

• fromInteger :: Integer -> Float/Double now consistently round to the nearest value, with ties to even.

• Additions to Data.Bits:

  • Newtypes And, Ior, Xor and Iff which wrap their argument, and whose Semigroup instances are defined using (.&.), (.|.), xor and \x y -> complement (x `xor` y), respectively.

  • oneBits :: FiniteBits a => a, oneBits = complement zeroBits.

4.15.0.0 Feb 2021

• Shipped with GHC 9.0.1

• openFile now calls the open system call with an interruptible FFI call, ensuring that the call can be interrupted with SIGINT on POSIX systems.

• Make openFile more tolerant of asynchronous exceptions: more care taken to release the file descriptor and the read/write lock (#18832)

• Add hGetContents', getContents', and readFile' in System.IO: Strict IO variants of hGetContents, getContents, and readFile.

• Add singleton function for Data.List.NonEmpty.

• The planned deprecation of Data.Monoid.First and Data.Monoid.Last is scrapped due to difficulties with the suggested migration path.

• Data.Semigroup.Option and the accompanying option function are deprecated and scheduled for removal in 4.16.

• Add Generic instances to Fingerprint, GiveGCStats, GCFlags, ConcFlags, DebugFlags, CCFlags, DoHeapProfile, ProfFlags, DoTrace, TraceFlags, TickyFlags, ParFlags, RTSFlags, RTSStats, GCStats, ByteOrder, GeneralCategory, SrcLoc

• Add rules unpackUtf8, unpack-listUtf8 and unpack-appendUtf8 to GHC.Base. They correspond to their ascii versions and hopefully make it easier for libraries to handle utf8 encoded strings efficiently.

• An issue with list fusion and elem was fixed. elem applied to known small lists will now compile to a simple case statement more often.

• Add MonadFix and MonadZip instances for Complex

• Add Ix instances for tuples of size 6 through 15

• Correct Bounded instance and remove Enum and Integral instances for Data.Ord.Down.

• catMaybes is now implemented using mapMaybe, so that it is both a “good consumer” and “good producer” for list-fusion (#18574)

• Foreign.ForeignPtr.withForeignPtr is now less aggressively optimised, avoiding the soundness issue reported in #17760 in exchange for a small amount more allocation. If your application regresses significantly and the continuation given to withForeignPtr will not provably diverge then the previous optimisation behavior can be recovered by instead using GHC.ForeignPtr.unsafeWithForeignPtr.

• Correct Bounded instance and remove Enum and Integral instances for Data.Ord.Down.

• Data.Foldable methods maximum{,By}, minimum{,By}, product and sum are now stricter by default, as well as in the class implementation for List.

4.14.0.0 Jan 2020

• Bundled with GHC 8.10.1

• Add a TestEquality instance for the Compose newtype.

• Data.Ord.Down now has a field name, getDown

• Add Bits, Bounded, Enum, FiniteBits, Floating, Fractional, Integral, Ix, Real, RealFrac, RealFloat and Storable instances to Data.Ord.Down.

• Fix the integer-gmp variant of isValidNatural: Previously it would fail to detect values <= maxBound::Word that were incorrectly encoded using the NatJ# constructor.

• The type of coerce has been generalized. It is now runtime-representation polymorphic: forall {r :: RuntimeRep} (a :: TYPE r) (b :: TYPE r). Coercible a b => a -> b. The type argument r is marked as Inferred to prevent it from interfering with visible type application.

• Make Fixed and HasResolution poly-kinded.

• Add HasResolution instances for Nats.

• Add Functor, Applicative, Monad, Alternative, MonadPlus, Generic and Generic1 instances to Kleisli

• openTempFile is now fully atomic and thread-safe on Windows.

• Add isResourceVanishedError, resourceVanishedErrorType, and isResourceVanishedErrorType to System.IO.Error.

• Add newtypes for CSocklen (socklen_t) and CNfds (nfds_t) to System.Posix.Types.

• Add Functor, Applicative and Monad instances to (,,) a b and (,,,) a b c.

• Add resizeSmallMutableArray# to GHC.Exts.

• Add a Data instance to WrappedArrow, WrappedMonad, and ZipList.

• Add IsList instance for ZipList.

4.13.0.0 July 2019

• Bundled with GHC 8.8.1

• The final phase of the MonadFail proposal has been implemented:

  • The fail method of Monad has been removed in favor of the method of the same name in the MonadFail class.

  • MonadFail(fail) is now re-exported from the Prelude and Control.Monad modules.

• Fix Show instance of Data.Fixed: Negative numbers are now parenthesized according to their surrounding context. I.e. Data.Fixed.show produces syntactically correct Haskell for expressions like Just (-1 :: Fixed E2). (#16031)

• Support the characters from recent versions of Unicode (up to v. 12) in literals (#5518).

• The StableName type parameter now has a phantom role instead of a representational one. There is really no reason to care about the type of the underlying object.

• Add foldMap', a strict version of foldMap, to Foldable.

• The shiftL and shiftR methods in the Bits instances of Int, IntN, Word, and WordN now throw an overflow exception for negative shift values (instead of being undefined behaviour).

• scanr no longer crashes when passed a fusable, infinite list. (#16943)

4.12.0.0 21 September 2018

• Bundled with GHC 8.6.1

• The STM invariant-checking mechanism (always and alwaysSucceeds), which was deprecated in GHC 8.4, has been removed (as proposed in https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0011-deprecate-stm-invariants.rst). This is a bit earlier than proposed in the deprecation pragma included in GHC 8.4, but due to community feedback we decided to move ahead with the early removal.

  Existing users are encouraged to encapsulate their STM operations in safe abstractions which can perform the invariant checking without help from the runtime system.

• Add a new module GHC.ResponseFile (previously defined in the haddock package). (#13896)

• Move the module Data.Functor.Contravariant from the contravariant package to base.

• ($!) is now representation-polymorphic like ($).

• Add Applicative (for K1), Semigroup and Monoid instances in GHC.Generics. (#14849)

• asinh for Float and Double is now numerically stable in the face of non-small negative arguments and enormous arguments of either sign. (#14927)

• Numeric.showEFloat (Just 0) now respects the user’s requested precision. (#15115)

• Data.Monoid.Alt now has Foldable and Traversable instances. (#15099)

• Data.Monoid.Ap has been introduced

• Control.Exception.throw is now levity polymorphic. (#15180)

• Data.Ord.Down now has a number of new instances. These include: MonadFix, MonadZip, Data, Foldable, Traversable, Eq1, Ord1, Read1, Show1, Generic, Generic1. (#15098)

4.11.1.0 19 April 2018

• Bundled with GHC 8.4.2

• Add the readFieldHash function to GHC.Read which behaves like readField, but for a field that ends with a # symbol (#14918).

4.11.0.0 8 March 2018

• 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).

• Add a FixIOException data type to Control.Exception.Base, and change fixIO to throw that instead of a BlockedIndefinitelyOnMVar exception (#14356).

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.BifoldableandData.Bitraversable(previously defined in thebifunctors` 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 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 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)

• The bitSize method of Data.Bits.Bits now has a (partial!) default implementation based on bitSizeMaybe. (#12970)

New instances

• 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.

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 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)

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).