Modulevinyl-0.14.3Haskell2010

Data.Vinyl.ARec.Internal

Constant-time field accessors for extensible records. The trade-off is the usual lists vs arrays one: it is fast to add an element to the head of a list, but element access is linear time; array access time is uniform, but extending the array is more slower.

Tradeoffs:

No sharing of the spine (i.e. when you change elements in the front of the record the tail can't be re-used)
ARec requires (4 + n) words + size of the fields
1 for the ARec constructor
1 for the pointer to the SmallArray#
The SmallArray# has 2 words as header (1 for GC, 1 for number of elements)
1 pointer per element to the actual data
Rec requires (2n) words + size of Fields
1 word per (:&) constructor
1 word for the pointer to the element

2 types
2 classes
12 values

Packagevinyl-0.14.3
Exports16
LanguageHaskell2010
LicenceMIT
SourceInternal.hs

newtypenewtype ARec (f :: k -> Type) (ts :: [k])

An array-backed extensible record with constant-time field access.

Constructors

ARec SmallArray

Instances9RecSubset, RecElem, Eq, Ord, Show, RecElemFCtx, …

(is ~ RImage rs ss, IndexWitnesses is, NatToInt (RLength rs)) => RecSubset ARec rs ss isDefined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal
RecElem ARec t t' (t ': ts) (t' ': ts) 'ZDefined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal
(RIndex t (s ': ts) ~ 'S i, NatToInt i, RecElem ARec t t' ts ts' i) => RecElem ARec t t' (s ': ts) (s ': ts') ('S i)Defined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal
(RPureConstrained (IndexableField rs) rs, RecApplicative rs, Eq (Rec f rs)) => Eq (ARec f rs)Defined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal
(RPureConstrained (IndexableField rs) rs, RecApplicative rs, Ord (Rec f rs)) => Ord (ARec f rs)Defined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal
(RPureConstrained (IndexableField rs) rs, RecApplicative rs, Show (Rec f rs)) => Show (ARec f rs)Defined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal
type RecElemFCtx ARec f = ()Defined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal
type RecElemFCtx ARec f = ()Defined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal
type RecSubsetFCtx ARec f = ()Defined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal

classclass ToARec (us :: [k]) where

Instances2ToARec

ToARec '[]Defined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal
ToARec us => ToARec (u ': us)Defined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal

classclass NatToInt (RIndex t ts) => IndexableField (ts :: [k]) (t :: k)

Defines a constraint that lets us index into an ARec in order to produce a Rec using fromARec.

Instances1IndexableField

NatToInt (RIndex t ts) => IndexableField ts tDefined in vinyl-0.14.3 · Data.Vinyl.ARec.Internal

valuearec :: NatToInt (RLength us) => ARecBuilder f us -> ARec f us

Turn an ARecBuilder into an ARec

See ARecBuilder

newtypenewtype ARecBuilder (f :: k) (us :: k1)

An efficient builder for ARec values

Use the pseudo-constructors arcons and arnil to construct an ARecBuilder and then turn it into an ARec with arec

Example: (requires -XOverloadedLabels and )

user :: ARec ElField '[ "name"   ::: String
                      , "age"    ::: Int
                      , "active" ::: Bool]
user = arec (  #name   =: "Peter"
            `arcons` #age    =: 4
            `arcons` #active =: True
            `arcons` arnil
            )

Constructors

ARecBuilder (forall s. Int -> SmallMutableArray s -> ST s ())

valuearcons :: f u -> ARecBuilder f us -> ARecBuilder f (u ': us)

Pseudo-constructor for an ARecBuilder

Cons a field to an ARec under construction

See ARecBuilder

valuearnil :: ARecBuilder f '[]

Pseudo-constructor for ARecBuilder

Build an ARec without fields

See ARecBuilder

valuetoARec :: (NatToInt (RLength ts), ToARec ts) => Rec f ts -> ARec f ts

Convert a Rec into an ARec for constant-time field access.

valuefromARec

:: (RecApplicative ts, RPureConstrained (IndexableField ts) ts)
=> ARec f ts
-> Rec f ts

Convert an ARec into a Rec.

valueaget :: NatToInt (RIndex t ts) => ARec f ts -> f t

Get a field from an ARec.

valueunsafeAput :: NatToInt (RIndex t ts) => f t' -> ARec f ts -> ARec f ts'

Set a field in an ARec.

valueunsafeAlens

:: (Functor g, NatToInt (RIndex t ts))
=> f t -> g (f t')
-> ARec f ts
-> g (ARec f ts')

Define a lens for a field of an ARec.

valuearecGetSubset

:: (IndexWitnesses (RImage rs ss), NatToInt (RLength rs))
=> ARec f ss
-> ARec f rs

Get a subset of a record's fields.

valuearecSetSubset

:: IndexWitnesses (RImage rs ss)
=> ARec f ss
-> ARec f rs
-> ARec f ss

Set a subset of a larger record's fields to all of the fields of a smaller record.

valuearecRepsMatchCoercion :: AllRepsMatch f xs g ys => Coercion (ARec f xs) (ARec g ys)

Given that xs and ys have the same length, and mapping f over xs and g over ys produces lists whose elements are pairwise Coercible, ARec f xs and ARec g ys are Coercible.

valuearecConsMatchCoercion :: (forall (x :: k). Coercible (f x) (g x)) => Coercion (ARec f xs) (ARec g xs)

Given that forall x. Coercible (f x) (g x), produce a coercion from ARec f xs to ARec g xs. While the constraint looks a lot like Coercible f g, it is actually weaker.