Distribution.Compat.Newtype

Per Conor McBride, the Newtype typeclass represents the packing and unpacking of a newtype, and allows you to operate under that newtype with functions such as ala.

Documentation

class Newtype o n | n -> o where

The FunctionalDependencies version of Newtype type-class.

Since Cabal-3.0 class arguments are in a different order than in newtype package. This change is to allow usage with DeriveAnyClass (and DerivingStrategies, in GHC-8.2). Unfortunately one has to repeat inner type.

newtype New = New Old
  deriving anyclass (Newtype Old)

Another approach would be to use TypeFamilies (and possibly compute inner type using GHC.Generics), but we think FunctionalDependencies version gives cleaner type signatures.

Minimal complete definition

Nothing

Methods

pack :: o -> n

default pack :: Coercible o n => o -> n

unpack :: n -> o

default unpack :: Coercible n o => n -> o

Instances

Newtype CabalSpecVersion SpecVersion

Defined in Distribution.FieldGrammar.Newtypes

Methods

pack :: CabalSpecVersion -> SpecVersion

unpack :: SpecVersion -> CabalSpecVersion

Newtype String FilePathNT

Defined in Distribution.FieldGrammar.Newtypes

Methods

pack :: String -> FilePathNT

unpack :: FilePathNT -> String

Newtype String Token

Defined in Distribution.FieldGrammar.Newtypes

Methods

pack :: String -> Token

unpack :: Token -> String

Newtype String Token'

Defined in Distribution.FieldGrammar.Newtypes

Methods

pack :: String -> Token'

unpack :: Token' -> String

Newtype String CompatFilePath

Defined in Distribution.PackageDescription.FieldGrammar

Methods

pack :: String -> CompatFilePath

unpack :: CompatFilePath -> String

Newtype a (MQuoted a)

Defined in Distribution.FieldGrammar.Newtypes

Methods

pack :: a -> MQuoted a

unpack :: MQuoted a -> a

Newtype a (Identity a)

Defined in Distribution.Compat.Newtype

Methods

pack :: a -> Identity a

unpack :: Identity a -> a

Newtype a (Product a)

Defined in Distribution.Compat.Newtype

Methods

pack :: a -> Product a

unpack :: Product a -> a

Newtype a (Sum a)

Defined in Distribution.Compat.Newtype

Methods

pack :: a -> Sum a

unpack :: Sum a -> a

Newtype [SymbolicPath PackageDir LicenseFile] CompatLicenseFile

Defined in Distribution.PackageDescription.FieldGrammar

Methods

pack :: [SymbolicPath PackageDir LicenseFile] -> CompatLicenseFile

unpack :: CompatLicenseFile -> [SymbolicPath PackageDir LicenseFile]

Newtype (Set a) (Set' sep wrapper a)

Defined in Distribution.FieldGrammar.Newtypes

Methods

pack :: Set a -> Set' sep wrapper a

unpack :: Set' sep wrapper a -> Set a

Newtype (NonEmpty a) (NonEmpty' sep wrapper a)

Defined in Distribution.FieldGrammar.Newtypes

Methods

pack :: NonEmpty a -> NonEmpty' sep wrapper a

unpack :: NonEmpty' sep wrapper a -> NonEmpty a

Newtype [a] (List sep wrapper a)

Defined in Distribution.FieldGrammar.Newtypes

Methods

pack :: [a] -> List sep wrapper a

unpack :: List sep wrapper a -> [a]

Newtype (Either License License) SpecLicense

Defined in Distribution.FieldGrammar.Newtypes

Methods

pack :: Either License0 License -> SpecLicense

unpack :: SpecLicense -> Either License0 License

Newtype (CompilerFlavor, VersionRange) TestedWith

Defined in Distribution.FieldGrammar.Newtypes

Methods

pack :: (CompilerFlavor, VersionRange) -> TestedWith

unpack :: TestedWith -> (CompilerFlavor, VersionRange)

Newtype (a -> a) (Endo a)

Defined in Distribution.Compat.Newtype

Methods

pack :: (a -> a) -> Endo a

unpack :: Endo a -> a -> a

ala :: (Newtype o n, Newtype o' n') => (o -> n) -> ((o -> n) -> b -> n') -> b -> o'

>>> ala Sum foldMap [1, 2, 3, 4 :: Int]
10

Note: the user supplied function for the newtype is ignored.

>>> ala (Sum . (+1)) foldMap [1, 2, 3, 4 :: Int]
10

alaf :: (Newtype o n, Newtype o' n') => (o -> n) -> ((a -> n) -> b -> n') -> (a -> o) -> b -> o'

>>> alaf Sum foldMap length ["cabal", "install"]
12

Note: as with ala, the user supplied function for the newtype is ignored.

pack' :: Newtype o n => (o -> n) -> o -> n

Variant of pack, which takes a phantom type.

unpack' :: Newtype o n => (o -> n) -> n -> o

Variant of unpack, which takes a phantom type.