Modulegeneric-optics-2.3.0.0Haskell2010

Data.Generics.Sum.Typed

Derive constructor-field-type-based prisms generically.

1 class

Packagegeneric-optics-2.3.0.0
Exports1
LanguageHaskell2010
LicenceBSD-3-Clause
SourceTyped.hs

Prisms

1 declaration

Example6 expressions

>>> :set -XTypeApplications>>> :set -XDataKinds>>> :set -XDeriveGeneric>>> import GHC.Generics>>> import Optics.Core>>> :{data Animal  = Dog Dog  | Cat Name Age  | Duck Age  | Turtle Age  deriving (Generic, Show)data Dog  = MkDog  { name :: Name  , age  :: Age  }  deriving (Generic, Show)type Name = Stringnewtype Age  = Age Int deriving Showdog, cat, duck :: Animaldog = Dog (MkDog "Shep" (Age 3))cat = Cat "Mog" (Age 5)duck = Duck (Age 2):}

classclass AsType a s where

Types that can represent another type, either by being a sum with a constructor containing that type, or by actually being that type.

Methods

_Typed :: Prism' s a

A prism that projects a constructor uniquely identifiable by the type of its field.

Example3 expressions

>>> dog ^? _Typed @DogJust (MkDog {name = "Shep", age = Age 3})>>> cat ^? _Typed @(Name, Age)Just ("Mog",Age 5)>>> dog ^? _Typed @Age......... The type Animal contains multiple constructors whose fields are of type Age.... The choice of constructor is thus ambiguous, could be any of:... Duck... Turtle...

injectTyped :: a -> s

Inject by type.

Example2 expressions

>>> :{dog :: Dogdog = MkDog "Fido" (Age 11)dogAsAnimal :: AnimaldogAsAnimal = injectTyped dogdogAsItself :: DogdogAsItself = injectTyped dog>>> :}

projectTyped :: s -> Maybe a

Project by type.

Example2 expressions

>>> :{dogAsAnimal :: AnimaldogAsAnimal = Dog (MkDog "Fido" (Age 11))mDog :: Maybe DogmDog = projectTyped dogAsAnimal>>> :}

Instances4AsType

Context a s => AsType a sDefined in generic-optics-2.3.0.0 · Data.Generics.Sum.Typed
AsType Void aDefined in generic-optics-2.3.0.0 · Data.Generics.Sum.Typed
Uncluttering type signatures (see Void)
Example1 expression
```
>>> :t _Typed @Int_Typed @Int :: AsType Int s => Prism' s Int
```
AsType a VoidDefined in generic-optics-2.3.0.0 · Data.Generics.Sum.Typed
Uncluttering type signatures (see Void)
Example1 expression
```
>>> :t _Typed_Typed :: AsType a s => Prism' s a
```
AsType a aDefined in generic-optics-2.3.0.0 · Data.Generics.Sum.Typed
Every type can be treated as itself.