Modulegeneric-lens-2.3.0.0Haskell2010

Data.Generics.Product.Typed

Derive lenses of a given type in a product.

1 class

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

Lenses

1 declaration

Running example:

Example6 expressions

>>> :set -XTypeApplications>>> :set -XDataKinds>>> :set -XDeriveGeneric>>> import GHC.Generics>>> :m +Data.Generics.Internal.VL.Lens>>> :{data Human  = Human    { name    :: String    , age     :: Int    , address :: String    , tall    :: Bool    }  | HumanNoTall    { name    :: String    , age     :: Int    , address :: String    }  deriving (Generic, Show)human :: Humanhuman = Human "Tunyasz" 50 "London" False:}

classclass HasType a s where

Types that contain another type, either by being a record with a field with that type, or by actually being that type.

Methods

typed :: Lens s s a a

A lens that focuses on a field with a unique type in its parent type. Compatible with the lens package's Control.Lens.Lens type.

Example1 expression

>>> human ^. typed @Int50

Type errors

Example1 expression

>>> human ^. typed @String......... The type Human contains multiple values of type [Char].... The choice of value is thus ambiguous. The offending constructors are:... Human... HumanNoTall...

Example1 expression

>>> human ^. typed @Bool......... Not all constructors of the type Human contain a field of type Bool.... The offending constructors are:... HumanNoTall...

getTyped :: s -> a
Get field at type.
setTyped :: a -> s -> s
Set field at type.

Instances3HasType

HasType a VoidDefined in generic-lens-2.3.0.0 · Data.Generics.Product.Typed
Uncluttering type signatures (see Void)
Example1 expression
```
>>> :t +d typedtyped :: (HasType a s, Functor f) => (a -> f a) -> s -> f s
```
Note that this might not longer be needed given the 'HasType a a' instance.
HasType a aDefined in generic-lens-2.3.0.0 · Data.Generics.Product.Typed
Every type has itself.
Context a s => HasType a sDefined in generic-lens-2.3.0.0 · Data.Generics.Product.Typed