Readme for base-compat-0.8.2
A compatibility layer for base
Scope
The scope of base-compat
is to provide functions available in later versions
of base to a wider (older) range of compilers.
In addition, successful library proposals that have been accepted to be part of
upcoming versions of base
are also included. This package is not intended to
replace base
, but to complement it.
Note that base-compat
does not add any orphan instances. There is a separate
package base-orphans
for
that.
Basic usage
In your cabal file, you should have something like this:
build-depends: base >= 4.3
, base-compat >= 0.8.0
Then, lets say you want to use the isRight
function introduced with
base-4.7.0.0
. Replace:
import Data.Either
with
import Data.Either.Compat
Note (1): There is no need to import both unqualified. The .Compat
modules
re-exports the original module.
Note (2): If a given module .Compat
version is not defined, that either
means that:
- The module has not changed in recent base versions, thus no
.Compat
is needed. - The module has changed, but the changes depend on newer versions of GHC, and thus are not portable.
- The module has changed, but those changes have not yet been merged in
base-compat
: patches are welcomed!
Using Prelude.Compat
If you want to use Prelude.Compat
(which provides all the
AMP/Traversable/Foldable changes from base-4.8.0.0
), it's best to hide
Prelude
, e.g.:
import Prelude ()
import Prelude.Compat
main :: IO ()
main = mapM_ print (Just 23)
Alternatively, you can use the NoImplicitPrelude
language extension:
{-# LANGUAGE NoImplicitPrelude #-}
import Prelude.Compat
main :: IO ()
main = mapM_ print (Just 23)
Note that we use
mapM_ :: (Foldable t, Monad m) => (a -> m b) -> t a -> m ()
from Data.Foldable
here, which is only exposed from Prelude
since
base-4.8.0.0
.
Using this approach allows you to write code that works seamlessly with all
versions of GHC that are supported by base-compat
.
What is covered
So far the following is covered.
For compatibility with the latest released version of base
Prelude.Compat
incorporates the AMP/Foldable/Traversable changes and exposes the same interface asPrelude
frombase-4.8.0.0
System.IO.Error.catch
is not re-exported fromPrelude.Compat
for older versions ofbase
Text.Read.Compat.readMaybe
Text.Read.Compat.readEither
Data.Monoid.Compat.<>
- Added
bitDefault
,testBitDefault
, andpopCountDefault
toData.Bits.Compat
- Added
toIntegralSized
toData.Bits.Compat
(if usingbase-4.7
) - Added
bool
function toData.Bool.Compat
- Added
isLeft
andisRight
toData.Either.Compat
- Added
withMVarMasked
function toControl.Concurrent.MVar.Compat
- Added
(<$!>)
function toControl.Monad.Compat
- Added
($>)
andvoid
functions toData.Functor.Compat
(&)
function toData.Function.Compat
($>)
andvoid
functions toData.Functor.Compat
dropWhileEnd
,isSubsequenceOf
,sortOn
, anduncons
functions toData.List.Compat
- Correct versions of
nub
,nubBy
,union
, andunionBy
toData.List.Compat
makeVersion
function toData.Version.Compat
traceId
,traceShowId
,traceM
, andtraceShowM
functions toDebug.Trace.Compat
byteSwap16
,byteSwap32
, andbyteSwap64
toData.Word.Compat
calloc
andcallocBytes
functions toForeign.Marshal.Alloc.Compat
callocArray
andcallocArray0
functions toForeign.Marshal.Array.Compat
fillBytes
toForeign.Marshal.Utils.Compat
- Added
Data.List.Compat.scanl'
showFFloatAlt
andshowGFloatAlt
toNumeric.Compat
lookupEnv
,setEnv
andunsetEnv
toSystem.Environment.Compat
Supported versions of GHC/base
ghc-7.10.1
/base-4.8.0.0
ghc-7.8.4
/base-4.7.0.2
ghc-7.8.3
/base-4.7.0.1
ghc-7.8.2
/base-4.7.0.0
ghc-7.8.1
/base-4.7.0.0
ghc-7.6.3
/base-4.6.0.1
ghc-7.6.2
/base-4.6.0.1
ghc-7.6.1
/base-4.6.0.0
ghc-7.4.2
/base-4.5.1.0
ghc-7.4.1
/base-4.5.0.0
ghc-7.2.2
/base-4.4.1.0
ghc-7.2.1
/base-4.4.0.0
ghc-7.0.4
/base-4.3.1.0
ghc-7.0.3
/base-4.3.1.0
ghc-7.0.2
/base-4.3.1.0
ghc-7.0.1
/base-4.3.0.0
Patches are welcome; add tests for new code!
Development
For Prelude.Compat
there is an Prelude.index
file that was generated from
the output of
ghc --show-iface Prelude.hi
To verify that Prelude.Compat
matches the specification given in
Prelude.types
run:
./check-Prelude.sh