Documentation

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.

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

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

Variant of pack, which takes a phantom type.

Variant of unpack, which takes a phantom type.