5f262ef · generic-lens

git.iko.soy/generic-lens

subtype -> super

commit5f262ef6a6e9d2ab6af7be9df9c062e63019a7c2 authorCsongor Kiss <kiss.csongor.kiss@gmail.com> dateSun 11 Jun 2017, 11:56 (9 years ago) parent6279123

5 files changed+15−12

compare with master

unifiedsplit

README.md+6−6 generic-lens.cabal+2 src/Data/Generics/Internal/Lens.hs+1 src/Data/Generics/Record.hs+1−1 src/Data/Generics/Record/Subtype.hs+5−5

README.md+6−6

@@ -75,7 +75,7 @@ True

7575

7676## Structural subtyping

7777

78−A record is a (structural) `subtype' of another, if its fields are a subset of

78+A record is a (structural) `subtype' of another, if its fields are a superset of

7979those of the other.

8080

8181```haskell

@@ -103,18 +103,18 @@ Animal {name = "Tunyasz", age = 50}

103103>>> smash (Animal "dog" 10) human

104104Human {name = "dog", age = 10, address = "London"}

105105

106−-- 'subtype' is a lens that focuses on a subrecord of a larger record:

107−>>> human ^. subtype @Animal

106+-- 'super' is a lens that focuses on a subrecord of a larger record:

107+>>> human ^. super @Animal

108108Animal {name = "Tunyasz", age = 50}

109109```

110110

111−We can apply a function that operates on a subtype to the larger structure,

112−by focusing on the subtype first:

111+We can apply a function that operates on a supertype to the larger (subtype)

112+structure, by focusing on the supertype first:

113113

114114```haskell

115115growUp :: Animal -> Animal

116116growUp (Animal name age) = Animal name (age + 50)

117117

118−>>> human & subtype @Animal %~ growUp

118+>>> human & super @Animal %~ growUp

119119Human {name = "Tunyasz", age = 60, address = "London"}

120120```

generic-lens.cabal+2

@@ -53,6 +53,8 @@ library

5353

5454 -- Other library packages from which modules are imported.

5555 build-depends: base >= 4.9 && <= 5.0

56+ , lens

57+ , kan-extensions

5658

5759 -- Directories containing source files.

5860 hs-source-dirs: src

src/Data/Generics/Internal/Lens.hs+1

@@ -34,6 +34,7 @@ type Lens' s a

3434-- | Getting

3535(^.) :: s -> ((a -> Const a a) -> s -> Const a s) -> a

3636s ^. l = getConst (l Const s)

37+infixl 8 ^.

3738

3839-- | Setting

3940set :: ((a -> Identity b) -> s -> Identity t) -> b -> s -> t

src/Data/Generics/Record.hs+1−1

@@ -18,7 +18,7 @@ module Data.Generics.Record

1818 (

1919 -- * Subtype relationship

2020 Subtype (..)

21− , subtype

21+ , super

2222

2323 -- * Magic lens

2424 , HasField (..)

src/Data/Generics/Record/Subtype.hs+5−5

@@ -49,7 +49,7 @@

4949-----------------------------------------------------------------------------

5050module Data.Generics.Record.Subtype

5151 ( Subtype (..)

52− , subtype

52+ , super

5353 ) where

5454

5555import Data.Generics.Record.HasField

@@ -86,13 +86,13 @@ instance (GSmash (Rep a) (Rep b), GUpcast (Rep a) (Rep b), Generic a, Generic b)

8686-- | Structural subtype lens. Given a subtype relationship @sub :< sup@,

8787-- we can focus on the @sub@ structure of @sup@.

8888--

89−-- >>> human ^. subtype @Animal

89+-- >>> human ^. super @Animal

9090-- Animal {name = "Tunyasz", age = 50}

9191--

92−-- >>> set (subtype @Animal) (Animal "dog" 10) human

92+-- >>> set (super @Animal) (Animal "dog" 10) human

9393-- Human {name = "dog", age = 10, address = "London"}

94−subtype :: forall sup sub. Subtype sub sup => Lens' sub sup

95−subtype f sub = fmap (flip smash sub) (f (upcast sub))

94+super :: forall sup sub. Subtype sub sup => Lens' sub sup

95+super f sub = fmap (flip smash sub) (f (upcast sub))

9696

9797--------------------------------------------------------------------------------

9898-- * Generic upcasting