| 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.Product.Positions
Contents
Description
Derive positional product type getters and setters generically.
Synopsis
- class HasPosition (i :: Nat) s t a b | s i -> a, t i -> b, s i b -> t, t i a -> s where
- class HasPosition' (i :: Nat) s a | s i -> a where
- class HasPosition_ (i :: Nat) s t a b where
- class HasPosition0 (i :: Nat) s t a b where
- getPosition :: forall i s a. HasPosition' i s a => s -> a
- setPosition :: forall i s a. HasPosition' i s a => a -> s -> s
Lenses
Running example:
>>>:set -XTypeApplications>>>:set -XDataKinds>>>:set -XDeriveGeneric>>>:set -XGADTs>>>:set -XFlexibleContexts>>>import GHC.Generics>>>:m +Data.Generics.Internal.VL.Lens>>>:m +Data.Function>>>:{data Human = Human { name :: String , age :: Int , address :: String } deriving (Generic, Show) human :: Human human = Human "Tunyasz" 50 "London" :}
class HasPosition (i :: Nat) s t a b | s i -> a, t i -> b, s i b -> t, t i a -> s where Source #
Records that have a field at a given position.
Methods
position :: Lens s t a b Source #
A lens that focuses on a field at a given position. Compatible with the
lens package's Lens type.
>>>human ^. position @1"Tunyasz">>>human & position @3 .~ "Berlin"Human {name = "Tunyasz", age = 50, address = "Berlin"}
Type errors
>>>human & position @4 .~ "Berlin"... ... The type Human does not contain a field at position 4 ...
Instances
| (ErrorUnless i s ((0 <? i) && (i <=? Size (Rep s))), HasTotalPositionP i (CRep s) ~~ Just a, HasTotalPositionP i (CRep t) ~~ Just b, HasTotalPositionP i (CRep (Indexed s)) ~~ Just a', HasTotalPositionP i (CRep (Indexed t)) ~~ Just b', t ~~ Infer s a' b, s ~~ Infer t b' a, Coercible (CRep s) (Rep s), Coercible (CRep t) (Rep t), HasPosition0 i s t a b) => HasPosition i s t a b Source # | |
Defined in Data.Generics.Product.Positions | |
| HasPosition f (Void1 a) (Void1 b) a b Source # | See Note [Uncluttering type signatures] |
class HasPosition' (i :: Nat) s a | s i -> a where Source #
Records that have a field at a given position.
The difference between HasPosition and HasPosition_ is similar to the
one between HasField and
HasField_.
See HasField_.
Instances
| (Generic s, ErrorUnless i s ((0 <? i) && (i <=? Size (Rep s))), cs ~ CRep s, Coercible (Rep s) cs, GLens' (HasTotalPositionPSym i) cs a, Defined (Rep s) (NoGeneric s (Text "arising from a generic lens focusing on the field at" ': ((((((Text "position " :<>: QuoteType i) :<>: Text " of type ") :<>: QuoteType a) :<>: Text " in ") :<>: QuoteType s) ': ([] :: [ErrorMessage])))) ()) => HasPosition' i s a Source # | |
Defined in Data.Generics.Product.Positions | |
class HasPosition_ (i :: Nat) s t a b where Source #
class HasPosition0 (i :: Nat) s t a b where Source #
Records that have a field at a given position.
This class gives the minimal constraints needed to define this lens.
For common uses, see HasPosition.
Instances
| (Generic s, Generic t, GLens (HasTotalPositionPSym i) (CRep s) (CRep t) a b, Coercible (CRep s) (Rep s), Coercible (CRep t) (Rep t), Defined (Rep s) (NoGeneric s (Text "arising from a generic lens focusing on the field at" ': ((((((Text "position " :<>: QuoteType i) :<>: Text " of type ") :<>: QuoteType a) :<>: Text " in ") :<>: QuoteType s) ': ([] :: [ErrorMessage])))) ()) => HasPosition0 i s t a b Source # | |
Defined in Data.Generics.Product.Positions | |
getPosition :: forall i s a. HasPosition' i s a => s -> a Source #
>>>getPosition @2 human50
setPosition :: forall i s a. HasPosition' i s a => a -> s -> s Source #
>>>setPosition @2 60 humanHuman {name = "Tunyasz", age = 60, address = "London"}