Copyright	(C) 2017 Csongor Kiss
License	BSD3
Maintainer	Csongor Kiss <kiss.csongor.kiss@gmail.com>
Stability	experimental
Portability	non-portable
Safe Haskell	None
Language	Haskell2010

Data.Generics.Product.Typed

Contents

Lenses

Description

Derive lenses of a given type in a product.

Synopsis

class HasType a s where

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 Source #

Records that have a field with a unique type.

Minimal complete definition

typed | setTyped, getTyped

Methods

typed :: Lens s s a a Source #

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 Source #

Get field at type.

setTyped :: a -> s -> s Source #

Set field at type.

Instances

(Generic s, ErrorUnlessOne a s (CollectTotalType a (Rep s)), GLens (HasTotalTypePSym a) (Rep s) (Rep s) a a) => HasType a s Source #
Instance details Defined in Data.Generics.Product.Typed Methods typed :: Lens s s a a Source # getTyped :: s -> a Source # setTyped :: a -> s -> s Source #