Safe Haskell	Safe
Language	Haskell2010

Data.TypeLevelKVList

Contents

Constructors
Operators
Misc

Description

This module supply a way to construct type safe key-value pair list and convenient operations for the type.

Synopsis

Constructors

We can create type level KV list as follows.

>>> :set -XDataKinds -XTypeOperators
>>> let sampleList = (namedVal "str" :: NamedVal String "foo") :. (namedVal 34 :: NamedVal Int "bar") :. Null
>>> type SampleList = NamedVal String "foo" :. NamedVal Int "bar" :. Null

type NamedVal v key = (Proxy key, v) #

A value with type level key.

namedVal :: v -> NamedVal v k #

A convenient function to construct type level KV list.

data a :. b infixr 8 #

Type level list cons.

Constructors

a :. b infixr 8

Instances

(NamedList * b, KnownSymbol k) => NamedList * ((:.) (NamedVal Symbol v k) b) #
Associated Types type NamedList' ((:.) (NamedVal Symbol v k) b) (layout :: (:.) (NamedVal Symbol v k) b) :: * Methods keys :: Proxy (NamedVal Symbol v k :. b) layout -> [String] #
(Eq b, Eq a) => Eq ((:.) a b) #
Methods (==) :: (a :. b) -> (a :. b) -> Bool # (/=) :: (a :. b) -> (a :. b) -> Bool #
(Show b, Show a) => Show ((:.) a b) #
Methods showsPrec :: Int -> (a :. b) -> ShowS # show :: (a :. b) -> String # showList :: [a :. b] -> ShowS #

data Null #

Type level empty list.

Constructors

Null

Instances

Eq Null #
Methods (==) :: Null -> Null -> Bool # (/=) :: Null -> Null -> Bool #
Show Null #
Methods showsPrec :: Int -> Null -> ShowS # show :: Null -> String # showList :: [Null] -> ShowS #
NamedList * Null #
Associated Types type NamedList' Null (layout :: Null) :: * Methods keys :: Proxy Null layout -> [String] #

Operators

get :: HasKey list pkey (Lookup pkey list) => pkey -> list -> Lookup pkey list #

>>> get (Proxy :: Proxy "foo") sampleList
"str"

>>> get (Proxy :: Proxy "bar") sampleList
34

>>> get (Proxy :: Proxy "baz") sampleList
Null

type family Lookup pkey list where ... #

Type level lookup :: k -> [(k, a)] -> a.

Equations

Lookup pk ((pk, v) :. b) = v
Lookup pk ((px, v) :. b) = Lookup pk b
Lookup pk Null = Null

keys :: NamedList layout => Proxy layout -> [String] #

>>> keys (Proxy :: Proxy SampleList)
["foo","bar"]

keys' :: NamedList k => k -> [String] #

>>> keys' sampleList
["foo","bar"]

Misc

class NamedList layout where #

Main class for a list of values with type level key

Minimal complete definition

keys

Methods

keys :: Proxy layout -> [String] #

>>> keys (Proxy :: Proxy SampleList)
["foo","bar"]

Instances

NamedList * Null #
Associated Types type NamedList' Null (layout :: Null) :: * Methods keys :: Proxy Null layout -> [String] #
(NamedList * b, KnownSymbol k) => NamedList * ((:.) (NamedVal Symbol v k) b) #
Associated Types type NamedList' ((:.) (NamedVal Symbol v k) b) (layout :: (:.) (NamedVal Symbol v k) b) :: * Methods keys :: Proxy (NamedVal Symbol v k :. b) layout -> [String] #