| Copyright | (C) 2019 Csongor Kiss |
|---|---|
| License | BSD3 |
| Maintainer | Csongor Kiss <kiss.csongor.kiss@gmail.com> |
| Stability | experimental |
| Portability | non-portable |
| Safe Haskell | None |
| Language | Haskell2010 |
Data.Generics.Sum.Constructors
Contents
Description
Derive constructor-name-based prisms generically.
Synopsis
- class AsConstructor (ctor :: Symbol) s t a b | ctor s -> a, ctor t -> b where
- class AsConstructor_ (ctor :: Symbol) s t a b where
- class AsConstructor' (ctor :: Symbol) s a | ctor s -> a where
- class AsConstructor0 (ctor :: Symbol) s t a b where
Prisms
Running example:
>>>:set -XTypeApplications>>>:set -XDataKinds>>>:set -XDeriveGeneric>>>:set -XFlexibleContexts>>>:set -XTypeFamilies>>>import GHC.Generics>>>:m +Data.Generics.Internal.VL.Prism>>>:m +Data.Generics.Product.Fields>>>:m +Data.Function>>>:{data Animal a = Dog (Dog a) | Cat Name Age | Duck Age deriving (Generic, Show) data Dog a = MkDog { name :: Name , age :: Age , fieldA :: a } deriving Show type Name = String type Age = Int dog, cat, duck :: Animal Int dog = Dog (MkDog "Shep" 3 30) cat = Cat "Mog" 5 duck = Duck 2 :}
class AsConstructor (ctor :: Symbol) s t a b | ctor s -> a, ctor t -> b where Source #
Sums that have a constructor with a given name.
Methods
_Ctor :: Prism s t a b Source #
A prism that projects a named constructor from a sum. Compatible with the
lens package's Prism type.
>>>dog ^? _Ctor @"Dog"Just (MkDog {name = "Shep", age = 3, fieldA = 30})
>>>dog ^? _Ctor @"Cat"Nothing
>>>cat ^? _Ctor @"Cat"Just ("Mog",5)
>>>_Ctor @"Cat" # ("Garfield", 6) :: Animal IntCat "Garfield" 6
Type errors
>>>cat ^? _Ctor @"Turtle"... ... ... The type Animal Int does not contain a constructor named "Turtle" ...
Instances
| (ErrorUnless ctor s (HasCtorP ctor (Rep s)), GAsConstructor' ctor (Rep s) a, GAsConstructor' ctor (Rep (Indexed s)) a', GAsConstructor ctor (Rep s) (Rep t) a b, t ~ Infer s a' b, GAsConstructor' ctor (Rep (Indexed t)) b', s ~ Infer t b' a, AsConstructor0 ctor s t a b) => AsConstructor ctor s t a b Source # | |
Defined in Data.Generics.Sum.Constructors | |
| AsConstructor ctor (Void1 a) (Void1 b) a b Source # | See Note [Uncluttering type signatures] |
class AsConstructor_ (ctor :: Symbol) s t a b where Source #
Sums that have a constructor with a given name.
The difference between HasConstructor and HasConstructor_ is similar to
the one between HasField and
HasField_.
See HasField_.
Instances
| (ErrorUnless ctor s (HasCtorP ctor (Rep s)), GAsConstructor' ctor (Rep s) a, GAsConstructor' ctor (Rep (Indexed s)) a', GAsConstructor ctor (Rep s) (Rep t) a b, GAsConstructor' ctor (Rep (Indexed t)) b', UnifyHead s t, UnifyHead t s, AsConstructor0 ctor s t a b) => AsConstructor_ ctor s t a b Source # | |
Defined in Data.Generics.Sum.Constructors | |
| AsConstructor_ ctor (Void1 a) (Void1 b) a b Source # | |
class AsConstructor' (ctor :: Symbol) s a | ctor s -> a where Source #
Instances
| (Generic s, ErrorUnless ctor s (HasCtorP ctor (Rep s)), GAsConstructor' ctor (Rep s) a, Defined (Rep s) (NoGeneric s ((((Text "arising from a generic prism focusing on the " :<>: QuoteType ctor) :<>: Text " constructor of type ") :<>: QuoteType a) ': ((Text "in " :<>: QuoteType s) ': ([] :: [ErrorMessage])))) ()) => AsConstructor' ctor s a Source # | |
Defined in Data.Generics.Sum.Constructors | |
class AsConstructor0 (ctor :: Symbol) s t a b where Source #
Sums that have a constructor with a given name.
This class gives the minimal constraints needed to define this prism.
For common uses, see HasConstructor.
Instances
| (Generic s, Generic t, GAsConstructor ctor (Rep s) (Rep t) a b, Defined (Rep s) (NoGeneric s ((((Text "arising from a generic prism focusing on the " :<>: QuoteType ctor) :<>: Text " constructor of type ") :<>: QuoteType a) ': ((Text "in " :<>: QuoteType s) ': ([] :: [ErrorMessage])))) ()) => AsConstructor0 ctor s t a b Source # | |
Defined in Data.Generics.Sum.Constructors | |