Safe Haskell	None
Language	Haskell2010

Data.Vinyl.XRec

Description

A variant of Rec whose values have eliminated common syntactic clutter due to Identity, Compose, and ElField type constructors.

A common pain point with using Rec is the mandatory context of each value. A basic record might look like this, Identity "joe" :& Identity 23 :& RNil :: Rec Identity '[String, Int]. The Identity constructors are a nuisance, so we offer a way of avoiding them: "joe" ::& 23 ::& XRNil :: XRec Identity '[String,Int]. Facilities are provided for converting between XRec and Rec so that the Rec API is available even if you choose to use XRec for construction or pattern matching.

Synopsis

type XRec f = Rec (XData f)
pattern (::&) :: HKD f r -> XRec f rs -> XRec f (r ': rs)
pattern XRNil :: XRec f '[]
rmapX :: forall f g rs. (XRMap f g rs, IsoXRec f rs, IsoXRec g rs) => (forall a. HKD f a -> HKD g a) -> Rec f rs -> Rec g rs
rmapXEndo :: forall f rs. (XRMap f f rs, IsoXRec f rs) => (forall a. HKD f a -> HKD f a) -> Rec f rs -> Rec f rs
xrmap :: forall f g rs. XRMap f g rs => (forall a. HKD f a -> HKD g a) -> XRec f rs -> XRec g rs
newtype XData t a = XData {
- unX :: HKD t a
}
class XRMap f g rs where
- xrmapAux :: (forall a. XData f a -> XData g a) -> XRec f rs -> XRec g rs
class XRApply f g rs where
- xrapply :: XRec (Lift (->) f g) rs -> XRec f rs -> XRec g rs
class IsoXRec f ts where
- fromXRec :: XRec f ts -> Rec f ts
- toXRec :: Rec f ts -> XRec f ts
class IsoHKD f a where
- type HKD f a
- unHKD :: HKD f a -> f a
- toHKD :: f a -> HKD f a
rgetX :: forall a record f rs. (RecElem record a a rs rs (RIndex a rs), RecElemFCtx record f, IsoHKD f a) => record f rs -> HKD f a

Documentation

type XRec f = Rec (XData f) Source #

pattern (::&) :: HKD f r -> XRec f rs -> XRec f (r ': rs) infixr 7 Source #

pattern XRNil :: XRec f '[] Source #

rmapX :: forall f g rs. (XRMap f g rs, IsoXRec f rs, IsoXRec g rs) => (forall a. HKD f a -> HKD g a) -> Rec f rs -> Rec g rs Source #

Like rmap, but the supplied function is written against the HKD-simplified types. This is xrmap sandwiched in between fromXRec and toXRec.

rmapXEndo :: forall f rs. (XRMap f f rs, IsoXRec f rs) => (forall a. HKD f a -> HKD f a) -> Rec f rs -> Rec f rs Source #

This is rmapX specialized to a type at which it does not change interpretation functor. This can help with type inference.

xrmap :: forall f g rs. XRMap f g rs => (forall a. HKD f a -> HKD g a) -> XRec f rs -> XRec g rs Source #

This is rmap for XRec. We apply a natural transformation between interpretation functors to transport a record value between interpretations.

newtype XData t a Source #

A wrapper for an HKD-simplified value. That is, noisy value constructors like Identity and Compose are ellided. This is used in the xrmapAux type class method, but may be ignored by users whose needs are met by xrmap and rmapX.

Constructors

XData
Fields unX :: HKD t a

class XRMap f g rs where Source #

The implementation of xrmap is broken into a type class to permit unrolling of the recursion across a record. The function mapped across the vector hides the HKD type family under a newtype constructor to help the type checker.

Methods

xrmapAux :: (forall a. XData f a -> XData g a) -> XRec f rs -> XRec g rs Source #

Instances

XRMap (f :: u -> Type) (g :: u -> Type) ([] :: [u]) Source #
Instance details Defined in Data.Vinyl.XRec Methods xrmapAux :: (forall (a :: u0). XData f a -> XData g a) -> XRec f [] -> XRec g [] Source #
(XRMap f g rs, IsoHKD f r, IsoHKD g r) => XRMap (f :: a -> Type) (g :: a -> Type) (r ': rs :: [a]) Source #
Instance details Defined in Data.Vinyl.XRec Methods xrmapAux :: (forall (a0 :: u). XData f a0 -> XData g a0) -> XRec f (r ': rs) -> XRec g (r ': rs) Source #

class XRApply f g rs where Source #

Like rapply: record of components f r -> g r may be applied to a record of f to get a record of g.

Methods

xrapply :: XRec (Lift (->) f g) rs -> XRec f rs -> XRec g rs Source #

Instances

XRApply (f :: u -> Type) (g :: u -> Type) ([] :: [u]) Source #
Instance details Defined in Data.Vinyl.XRec Methods xrapply :: XRec (Lift (->) f g) [] -> XRec f [] -> XRec g [] Source #
XRApply f g rs => XRApply (f :: a -> Type) (g :: a -> Type) (r ': rs :: [a]) Source #
Instance details Defined in Data.Vinyl.XRec Methods xrapply :: XRec (Lift (->) f g) (r ': rs) -> XRec f (r ': rs) -> XRec g (r ': rs) Source #

class IsoXRec f ts where Source #

Conversion between XRec and Rec. It is convenient to build and consume XRec values to reduce syntactic noise, but Rec has a richer API that is difficult to build around the HKD type family.

Methods

fromXRec :: XRec f ts -> Rec f ts Source #

toXRec :: Rec f ts -> XRec f ts Source #

Instances

IsoXRec (f :: u -> Type) ([] :: [u]) Source #
Instance details Defined in Data.Vinyl.XRec Methods fromXRec :: XRec f [] -> Rec f [] Source # toXRec :: Rec f [] -> XRec f [] Source #
(IsoXRec f ts, IsoHKD f t) => IsoXRec (f :: a -> Type) (t ': ts :: [a]) Source #
Instance details Defined in Data.Vinyl.XRec Methods fromXRec :: XRec f (t ': ts) -> Rec f (t ': ts) Source # toXRec :: Rec f (t ': ts) -> XRec f (t ': ts) Source #

class IsoHKD f a where Source #

Isomorphism between a syntactically noisy value and a concise one. For types like, Identity, we prefer to work with values of the underlying type without writing out the Identity constructor. For Compose f g a, aka (f :. g) a, we prefer to work directly with values of type f (g a).

This involves the so-called higher-kinded data type family. See http://reasonablypolymorphic.com/blog/higher-kinded-data for more discussion.

Minimal complete definition

Nothing

Associated Types

type HKD f a Source #

Methods

unHKD :: HKD f a -> f a Source #

unHKD :: HKD f a ~ f a => HKD f a -> f a Source #

toHKD :: f a -> HKD f a Source #

toHKD :: HKD f a ~ f a => f a -> HKD f a Source #

Instances

(IsoHKD f (HKD g a), IsoHKD g a, Functor f) => IsoHKD (Compose f g :: k -> Type) (a :: k) Source #	Work with values of type `Compose` `f g a` as if they were of type `f (g a)`.
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD (Compose f g) a :: Type Source # Methods unHKD :: HKD (Compose f g) a -> Compose f g a Source # toHKD :: Compose f g a -> HKD (Compose f g) a Source #
(IsoHKD f a, IsoHKD g a) => IsoHKD (Lift ((->) :: Type -> Type -> Type) f g :: k -> Type) (a :: k) Source #	Work with values of type `Lift` `(->) f g a` as if they were of type `f a -> g a`.
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD (Lift (->) f g) a :: Type Source # Methods unHKD :: HKD (Lift (->) f g) a -> Lift (->) f g a Source # toHKD :: Lift (->) f g a -> HKD (Lift (->) f g) a Source #
IsoHKD Maybe (a :: Type) Source #
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD Maybe a :: Type Source # Methods unHKD :: HKD Maybe a -> Maybe a Source # toHKD :: Maybe a -> HKD Maybe a Source #
IsoHKD IO (a :: Type) Source #
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD IO a :: Type Source # Methods unHKD :: HKD IO a -> IO a Source # toHKD :: IO a -> HKD IO a Source #
IsoHKD First (a :: Type) Source #
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD First a :: Type Source # Methods unHKD :: HKD First a -> First a Source # toHKD :: First a -> HKD First a Source #
IsoHKD Last (a :: Type) Source #
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD Last a :: Type Source # Methods unHKD :: HKD Last a -> Last a Source # toHKD :: Last a -> HKD Last a Source #
IsoHKD Sum (a :: Type) Source #	Work with values of type `Sum` `a` as if they were of type `a`.
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD Sum a :: Type Source # Methods unHKD :: HKD Sum a -> Sum a Source # toHKD :: Sum a -> HKD Sum a Source #
IsoHKD Product (a :: Type) Source #	Work with values of type `Product` `a` as if they were of type `a`.
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD Product a :: Type Source # Methods unHKD :: HKD Product a -> Product a Source # toHKD :: Product a -> HKD Product a Source #
IsoHKD Identity (a :: Type) Source #	Work with values of type `Identity` `a` as if they were simple of type `a`.
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD Identity a :: Type Source # Methods unHKD :: HKD Identity a -> Identity a Source # toHKD :: Identity a -> HKD Identity a Source #
IsoHKD (Either a :: Type -> Type) (b :: Type) Source #
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD (Either a) b :: Type Source # Methods unHKD :: HKD (Either a) b -> Either a b Source # toHKD :: Either a b -> HKD (Either a) b Source #
IsoHKD ((,) a :: Type -> Type) (b :: Type) Source #
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD ((,) a) b :: Type Source # Methods unHKD :: HKD ((,) a) b -> (a, b) Source # toHKD :: (a, b) -> HKD ((,) a) b Source #
KnownSymbol s => IsoHKD ElField ((,) s a :: (Symbol, Type)) Source #	Work with values of type `ElField` `'(s,a)` as if they were of type `a`.
Instance details Defined in Data.Vinyl.XRec Associated Types type HKD ElField (s, a) :: Type Source # Methods unHKD :: HKD ElField (s, a) -> ElField (s, a) Source # toHKD :: ElField (s, a) -> HKD ElField (s, a) Source #

rgetX :: forall a record f rs. (RecElem record a a rs rs (RIndex a rs), RecElemFCtx record f, IsoHKD f a) => record f rs -> HKD f a Source #

Record field getter that pipes the field value through HKD to eliminate redundant newtype wrappings. Usage will typically involve a visible type application to the field type. The definition is similar to, getHKD = toHKD . rget.