Data.Vinyl.Lens

Lenses into record fields.

Documentation

class (i ~ RIndex r rs, NatToInt i) => RecElem record (r :: k) (r' :: k) (rs :: [k]) (rs' :: [k]) (i :: Nat) | r r' rs i -> rs' where

The presence of a field in a record is witnessed by a lens into its value. The fifth parameter to RecElem, i, is there to help the constraint solver realize that this is a decidable predicate with respect to the judgemental equality in k.

Associated Types

type RecElemFCtx record (f :: k -> *) :: Constraint

An opportunity for instances to generate constraints based on the functor parameter of records passed to class methods.

Methods

rlensC :: (Functor g, RecElemFCtx record f) => (f r -> g (f r')) -> record f rs -> g (record f rs')

We can get a lens for getting and setting the value of a field which is in a record. As a convenience, we take a proxy argument to fix the particular field being viewed. These lenses are compatible with the lens library. Morally:

rlensC :: Lens' (Rec f rs) (Rec f rs') (f r) (f r')

rgetC :: (RecElemFCtx record f, r ~ r') => record f rs -> f r

For Vinyl users who are not using the lens package, we provide a getter.

rputC :: RecElemFCtx record f => f r' -> record f rs -> record f rs'

For Vinyl users who are not using the lens package, we also provide a setter. In general, it will be unambiguous what field is being written to, and so we do not take a proxy argument here.

Instances

RecElem (Rec :: (a -> Type) -> [a] -> Type) (r :: a) (r' :: a) (r ': rs :: [a]) (r' ': rs :: [a]) Z

Defined in Data.Vinyl.Lens

Associated Types

type RecElemFCtx Rec f :: Constraint

Methods

rlensC :: (Functor g, RecElemFCtx Rec f) => (f r -> g (f r')) -> Rec f (r ': rs) -> g (Rec f (r' ': rs))

rgetC :: (RecElemFCtx Rec f, r ~ r') => Rec f (r ': rs) -> f r

rputC :: RecElemFCtx Rec f => f r' -> Rec f (r ': rs) -> Rec f (r' ': rs)

RecElem (ARec :: (a -> Type) -> [a] -> Type) (t :: a) (t' :: a) (t ': ts :: [a]) (t' ': ts :: [a]) Z

Defined in Data.Vinyl.ARec

Associated Types

type RecElemFCtx ARec f :: Constraint

Methods

rlensC :: (Functor g, RecElemFCtx ARec f) => (f t -> g (f t')) -> ARec f (t ': ts) -> g (ARec f (t' ': ts))

rgetC :: (RecElemFCtx ARec f, t ~ t') => ARec f (t ': ts) -> f t

rputC :: RecElemFCtx ARec f => f t' -> ARec f (t ': ts) -> ARec f (t' ': ts)

(RIndex r (s ': rs) ~ S i, RecElem (Rec :: (a -> Type) -> [a] -> Type) r r' rs rs' i) => RecElem (Rec :: (a -> Type) -> [a] -> Type) (r :: a) (r' :: a) (s ': rs :: [a]) (s ': rs' :: [a]) (S i)

Defined in Data.Vinyl.Lens

Associated Types

type RecElemFCtx Rec f :: Constraint

Methods

rlensC :: (Functor g, RecElemFCtx Rec f) => (f r -> g (f r')) -> Rec f (s ': rs) -> g (Rec f (s ': rs'))

rgetC :: (RecElemFCtx Rec f, r ~ r') => Rec f (s ': rs) -> f r

rputC :: RecElemFCtx Rec f => f r' -> Rec f (s ': rs) -> Rec f (s ': rs')

(RIndex t (s ': ts) ~ S i, NatToInt i, RecElem (ARec :: (a -> Type) -> [a] -> Type) t t' ts ts' i) => RecElem (ARec :: (a -> Type) -> [a] -> Type) (t :: a) (t' :: a) (s ': ts :: [a]) (s ': ts' :: [a]) (S i)

Defined in Data.Vinyl.ARec

Associated Types

type RecElemFCtx ARec f :: Constraint

Methods

rlensC :: (Functor g, RecElemFCtx ARec f) => (f t -> g (f t')) -> ARec f (s ': ts) -> g (ARec f (s ': ts'))

rgetC :: (RecElemFCtx ARec f, t ~ t') => ARec f (s ': ts) -> f t

rputC :: RecElemFCtx ARec f => f t' -> ARec f (s ': ts) -> ARec f (s ': ts')

(i ~ RIndex t ts, NatToInt i, FieldOffset ElField ts t, Storable (Rec ElField ts), AllConstrained (FieldOffset ElField ts) ts) => RecElem (SRec :: ((Symbol, Type) -> Type) -> [(Symbol, Type)] -> Type) (t :: (Symbol, Type)) (t :: (Symbol, Type)) (ts :: [(Symbol, Type)]) (ts :: [(Symbol, Type)]) i

Defined in Data.Vinyl.SRec

Associated Types

type RecElemFCtx SRec f :: Constraint

Methods

rlensC :: (Functor g, RecElemFCtx SRec f) => (f t -> g (f t)) -> SRec f ts -> g (SRec f ts)

rgetC :: (RecElemFCtx SRec f, t ~ t) => SRec f ts -> f t

rputC :: RecElemFCtx SRec f => f t -> SRec f ts -> SRec f ts

(i ~ RIndex t ts, NatToInt i, FieldOffset ElField ts t, Storable (Rec ElField ts), AllConstrained (FieldOffset ElField ts) ts) => RecElem (SRec2 ElField) (t :: (Symbol, Type)) (t :: (Symbol, Type)) (ts :: [(Symbol, Type)]) (ts :: [(Symbol, Type)]) i

Field accessors for SRec2 specialized to ElField as the functor.

Defined in Data.Vinyl.SRec

Associated Types

type RecElemFCtx (SRec2 ElField) f :: Constraint

Methods

rlensC :: (Functor g, RecElemFCtx (SRec2 ElField) f) => (f t -> g (f t)) -> SRec2 ElField f ts -> g (SRec2 ElField f ts)

rgetC :: (RecElemFCtx (SRec2 ElField) f, t ~ t) => SRec2 ElField f ts -> f t

rputC :: RecElemFCtx (SRec2 ElField) f => f t -> SRec2 ElField f ts -> SRec2 ElField f ts

rget :: forall r rs f record. (RecElem record r r rs rs (RIndex r rs), RecElemFCtx record f) => record f rs -> f r

rput :: forall r rs record f. (RecElem record r r rs rs (RIndex r rs), RecElemFCtx record f) => f r -> record f rs -> record f rs

Type-preserving field setter. This type is simpler to work with than that of rput'.

rput' :: forall r r' rs rs' record f. (RecElem record r r' rs rs' (RIndex r rs), RecElemFCtx record f) => f r' -> record f rs -> record f rs'

The type-changing field setter rputC with the type arguments re-ordered for more convenient usage with TypeApplications.

rlens :: forall r record rs f g. (RecElem record r r rs rs (RIndex r rs), RecElemFCtx record f, Functor g) => (f r -> g (f r)) -> record f rs -> g (record f rs)

Type-preserving field lens. This type is simpler to work with than that of rlens'.

rlens' :: forall r r' record rs rs' f g. (RecElem record r r' rs rs' (RIndex r rs), RecElemFCtx record f, Functor g) => (f r -> g (f r')) -> record f rs -> g (record f rs')

Type-changing field lens rlensC with the type arguments re-ordered for more convenient usage with TypeApplications.

type RElem x rs = RecElem Rec x x rs rs

RecElem for classic vinyl Rec types.

class is ~ RImage rs ss => RecSubset record (rs :: [k]) (ss :: [k]) is where

If one field set is a subset another, then a lens of from the latter's record to the former's is evident. That is, we can either cast a larger record to a smaller one, or we may replace the values in a slice of a record.

Minimal complete definition

rsubsetC

Associated Types

type RecSubsetFCtx record (f :: k -> *) :: Constraint

An opportunity for instances to generate constraints based on the functor parameter of records passed to class methods.

Methods

rsubsetC :: (Functor g, RecSubsetFCtx record f) => (record f rs -> g (record f rs)) -> record f ss -> g (record f ss)

This is a lens into a slice of the larger record. Morally, we have:

rsubset :: Lens' (Rec f ss) (Rec f rs)

rcastC :: RecSubsetFCtx record f => record f ss -> record f rs

The getter of the rsubset lens is rcast, which takes a larger record to a smaller one by forgetting fields.

rreplaceC :: RecSubsetFCtx record f => record f rs -> record f ss -> record f ss

The setter of the rsubset lens is rreplace, which allows a slice of a record to be replaced with different values.

Instances

(is ~ RImage rs ss, IndexWitnesses is, NatToInt (RLength rs)) => RecSubset (ARec :: (k -> Type) -> [k] -> Type) (rs :: [k]) (ss :: [k]) is

Defined in Data.Vinyl.ARec

Associated Types

type RecSubsetFCtx ARec f :: Constraint

Methods

rsubsetC :: (Functor g, RecSubsetFCtx ARec f) => (ARec f rs -> g (ARec f rs)) -> ARec f ss -> g (ARec f ss)

rcastC :: RecSubsetFCtx ARec f => ARec f ss -> ARec f rs

rreplaceC :: RecSubsetFCtx ARec f => ARec f rs -> ARec f ss -> ARec f ss

RecSubset (Rec :: (k -> Type) -> [k] -> Type) ([] :: [k]) (ss :: [k]) ([] :: [Nat])

Defined in Data.Vinyl.Lens

Associated Types

type RecSubsetFCtx Rec f :: Constraint

Methods

rsubsetC :: (Functor g, RecSubsetFCtx Rec f) => (Rec f [] -> g (Rec f [])) -> Rec f ss -> g (Rec f ss)

rcastC :: RecSubsetFCtx Rec f => Rec f ss -> Rec f []

rreplaceC :: RecSubsetFCtx Rec f => Rec f [] -> Rec f ss -> Rec f ss

(RElem r ss i, RSubset rs ss is) => RecSubset (Rec :: (k -> Type) -> [k] -> Type) (r ': rs :: [k]) (ss :: [k]) (i ': is)

Defined in Data.Vinyl.Lens

Associated Types

type RecSubsetFCtx Rec f :: Constraint

Methods

rsubsetC :: (Functor g, RecSubsetFCtx Rec f) => (Rec f (r ': rs) -> g (Rec f (r ': rs))) -> Rec f ss -> g (Rec f ss)

rcastC :: RecSubsetFCtx Rec f => Rec f ss -> Rec f (r ': rs)

rreplaceC :: RecSubsetFCtx Rec f => Rec f (r ': rs) -> Rec f ss -> Rec f ss

(is ~ RImage rs ss, RecSubset (Rec :: ((Symbol, Type) -> Type) -> [(Symbol, Type)] -> Type) rs ss is, Storable (Rec ElField rs), Storable (Rec ElField ss), RPureConstrained (FieldOffset ElField ss) rs, RPureConstrained (FieldOffset ElField rs) rs, RFoldMap rs, RMap rs, RApply rs) => RecSubset (SRec :: ((Symbol, Type) -> Type) -> [(Symbol, Type)] -> Type) (rs :: [(Symbol, Type)]) (ss :: [(Symbol, Type)]) is

Defined in Data.Vinyl.SRec

Associated Types

type RecSubsetFCtx SRec f :: Constraint

Methods

rsubsetC :: (Functor g, RecSubsetFCtx SRec f) => (SRec f rs -> g (SRec f rs)) -> SRec f ss -> g (SRec f ss)

rcastC :: RecSubsetFCtx SRec f => SRec f ss -> SRec f rs

rreplaceC :: RecSubsetFCtx SRec f => SRec f rs -> SRec f ss -> SRec f ss

(is ~ RImage rs ss, RecSubset (Rec :: ((Symbol, Type) -> Type) -> [(Symbol, Type)] -> Type) rs ss is, Storable (Rec ElField rs), Storable (Rec ElField ss), RPureConstrained (FieldOffset ElField ss) rs, RPureConstrained (FieldOffset ElField rs) rs, RFoldMap rs, RMap rs, RApply rs) => RecSubset (SRec2 ElField) (rs :: [(Symbol, Type)]) (ss :: [(Symbol, Type)]) is

Defined in Data.Vinyl.SRec

Associated Types

type RecSubsetFCtx (SRec2 ElField) f :: Constraint

Methods

rsubsetC :: (Functor g, RecSubsetFCtx (SRec2 ElField) f) => (SRec2 ElField f rs -> g (SRec2 ElField f rs)) -> SRec2 ElField f ss -> g (SRec2 ElField f ss)

rcastC :: RecSubsetFCtx (SRec2 ElField) f => SRec2 ElField f ss -> SRec2 ElField f rs

rreplaceC :: RecSubsetFCtx (SRec2 ElField) f => SRec2 ElField f rs -> SRec2 ElField f ss -> SRec2 ElField f ss

rsubset :: forall rs ss f g record is. (RecSubset record (rs :: [k]) (ss :: [k]) is, Functor g, RecSubsetFCtx record f) => (record f rs -> g (record f rs)) -> record f ss -> g (record f ss)

A lens into a slice of the larger record. This is rsubsetC with the type arguments reordered for more convenient usage with TypeApplications.

rcast :: forall rs ss f record is. (RecSubset record rs ss is, RecSubsetFCtx record f) => record f ss -> record f rs

Takes a larger record to a smaller one by forgetting fields. This is rcastC with the type arguments reordered for more convenient usage with TypeApplications.

rreplace :: forall rs ss f record is. (RecSubset record rs ss is, RecSubsetFCtx record f) => record f rs -> record f ss -> record f ss

Allows a slice of a record to be replaced with different values. This is rreplaceC with the type arguments reordered for more convenient usage with TypeApplications.

rdowncast :: (RecApplicative ss, RMap rs, rs ⊆ ss) => Rec f rs -> Rec (Maybe :. f) ss

Takes a smaller record to a larger one, a downcast, by layering a Maybe interpretation that lets us use Nothing for the fields not present in the smaller record.

type RSubset = RecSubset Rec

type REquivalent rs ss is js = (RSubset rs ss is, RSubset ss rs js)

Two record types are equivalent when they are subtypes of each other.

type (∈) r rs = RElem r rs (RIndex r rs)

A shorthand for RElem which supplies its index.

type (⊆) rs ss = RSubset rs ss (RImage rs ss)

A shorthand for RSubset which supplies its image.

type (≅) rs ss = REquivalent rs ss (RImage rs ss) (RImage ss rs)

A shorthand for REquivalent which supplies its images.

type (<:) rs ss = rs ⊆ ss

A non-unicode equivalent of (⊆).

type (:~:) rs ss = rs ≅ ss

A non-unicode equivalent of (≅).