Data.Generics.Product.Typed

Derive lenses of a given type in a product.

Lenses

Running example:

>>> :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 :: Human
human = Human "Tunyasz" 50 "London" False
:}

class HasType a s where

Records that have a field with a unique type.

Minimal complete definition

typed | setTyped, getTyped

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 Lens type.

>>> human ^. typed @Int
50

Type errors

>>> 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
...

>>> 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.

Instances

HasType a Void

Uncluttering type signatures (see Void)

>>> :t +d typed
typed :: (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.

Defined in Data.Generics.Product.Typed

Methods

typed :: Lens Void Void a a

getTyped :: Void -> a

setTyped :: a -> Void -> Void

HasType a a

Defined in Data.Generics.Product.Typed

Methods

typed :: Lens a a a a

getTyped :: a -> a

setTyped :: a -> a -> a

Context a s => HasType a s

Defined in Data.Generics.Product.Typed

Methods

typed :: Lens s s a a

getTyped :: s -> a

setTyped :: a -> s -> s