Modulerelude-1.2.0.0Haskell2010

Relude.Extra.Newtype

SPDX-License-Identifier : MIT Maintainer : Kowainik xrom.xkov@gmail.com Stability : Stable Portability : Portable

Functions to ease work with newtypes.

6 values

Packagerelude-1.2.0.0
Exports6
LanguageHaskell2010
LicenceMIT
SourceNewtype.hs

valueun :: Coercible a n => n -> a

Unwraps value from newtype.

Example3 expressions

>>> newtype Size = Size Int deriving Show>>> un @Int (Size 5)5>>> un (Size 5) == length ['a', 'x', 'b']False

valuewrap :: Coercible a n => a -> n

Wraps value to newtype. Behaves exactly as un but has more meaningful name in case you need to convert some value to newtype.

Example2 expressions

>>> newtype Flag = Flag Bool deriving (Show, Eq)>>> wrap False == Flag TrueFalse

valueunder :: Coercible a n => (n -> n) -> a -> a

Applies function to the content of newtype. This function is not supposed to be used on newtypes that are created with the help of smart constructors.

Example4 expressions

>>> newtype Foo = Foo Bool deriving Show>>> under not (Foo True)Foo False>>> newtype Bar = Bar String deriving Show>>> under (filter (== 'a')) (Bar "abacaba")Bar "aaaa"

valueunder2 :: Coercible a n => (n -> n -> n) -> a -> a -> a

Lift binary function for newtypes to work over underlying newtype representation.

Example2 expressions

>>> under2 @(Sum Int) (<>) (3 :: Int) 47>>> under2 @All (<>) True FalseFalse

valueunderF2 :: Coercible a (n a) => (n a -> n a -> n a) -> a -> a -> a

Version of under2 that works on newtypes parametrized by their representation. Provided for convenience.

Example2 expressions

>>> underF2 @Sum (<>) (3 :: Int) 47>>> underF2 @Max (<>) 'p' 't''t'

value(#.) :: Coercible b c => (b -> c) -> (a -> b) -> a -> c

Coercible composition. This function allows to write more efficient implementations of function compositions over newtypes.