Safe Haskell	None
Language	Haskell2010

Data.Union

Description

Extensible type-safe unions.

>>> let a = openUnion # (5 :: Int) :: OpenUnion '[Bool, Int]

>>> a ^? openUnion @Int
Just 5

>>> a ^? openUnion @Bool
Nothing

>>> a ^? openUnion @Char
<interactive>:7:6: error:
    • No instance for (UElem Char '[] (RIndex Char '[]))
        arising from a use of ‘openUnion’
    • In the second argument of ‘(^?)’, namely ‘openUnion @Char’
      In the expression: a ^? openUnion @Char
      In an equation for ‘it’: it = a ^? openUnion @Char

Synopsis

data Union (f :: u -> *) (as :: [u]) where
- This :: !(f a) -> Union f (a ': as)
- That :: !(Union f as) -> Union f (a ': as)
union :: (Union f as -> c) -> (f a -> c) -> Union f (a ': as) -> c
absurdUnion :: Union f '[] -> a
umap :: (forall a. f a -> g a) -> Union f as -> Union g as
_This :: Prism (Union f (a ': as)) (Union f (b ': as)) (f a) (f b)
_That :: Prism (Union f (a ': as)) (Union f (a ': bs)) (Union f as) (Union f bs)
class i ~ RIndex a as => UElem (a :: u) (as :: [u]) (i :: Nat) where
class is ~ RImage as bs => USubset (as :: [u]) (bs :: [u]) is where
type OpenUnion = Union Identity
openUnion :: forall a as. UElem a as (RIndex a as) => Prism' (OpenUnion as) a

Documentation

data Union (f :: u -> *) (as :: [u]) where Source #

A union is parameterized by a universe u, an interpretation f and a list of labels as. The labels of the union are given by inhabitants of the kind u; the type of values at any label a :: u is given by its interpretation f a :: *.

Constructors

This :: !(f a) -> Union f (a ': as)
That :: !(Union f as) -> Union f (a ': as)

Instances

(Eq (f a2), Eq (Union f as)) => Eq (Union f (a2 ': as)) Source #
Instance details Defined in Data.Union Methods (==) :: Union f (a2 ': as) -> Union f (a2 ': as) -> Bool # (/=) :: Union f (a2 ': as) -> Union f (a2 ': as) -> Bool #
Eq (Union f ([] :: [u])) Source #
Instance details Defined in Data.Union Methods (==) :: Union f [] -> Union f [] -> Bool # (/=) :: Union f [] -> Union f [] -> Bool #
(Ord (f a2), Ord (Union f as)) => Ord (Union f (a2 ': as)) Source #
Instance details Defined in Data.Union Methods compare :: Union f (a2 ': as) -> Union f (a2 ': as) -> Ordering # (<) :: Union f (a2 ': as) -> Union f (a2 ': as) -> Bool # (<=) :: Union f (a2 ': as) -> Union f (a2 ': as) -> Bool # (>) :: Union f (a2 ': as) -> Union f (a2 ': as) -> Bool # (>=) :: Union f (a2 ': as) -> Union f (a2 ': as) -> Bool # max :: Union f (a2 ': as) -> Union f (a2 ': as) -> Union f (a2 ': as) # min :: Union f (a2 ': as) -> Union f (a2 ': as) -> Union f (a2 ': as) #
Ord (Union f ([] :: [u])) Source #
Instance details Defined in Data.Union Methods compare :: Union f [] -> Union f [] -> Ordering # (<) :: Union f [] -> Union f [] -> Bool # (<=) :: Union f [] -> Union f [] -> Bool # (>) :: Union f [] -> Union f [] -> Bool # (>=) :: Union f [] -> Union f [] -> Bool # max :: Union f [] -> Union f [] -> Union f [] # min :: Union f [] -> Union f [] -> Union f [] #
(Show (f a2), Show (Union f as)) => Show (Union f (a2 ': as)) Source #
Instance details Defined in Data.Union Methods showsPrec :: Int -> Union f (a2 ': as) -> ShowS # show :: Union f (a2 ': as) -> String # showList :: [Union f (a2 ': as)] -> ShowS #
Show (Union f ([] :: [u])) Source #
Instance details Defined in Data.Union Methods showsPrec :: Int -> Union f [] -> ShowS # show :: Union f [] -> String # showList :: [Union f []] -> ShowS #
Generic (Union f (a ': as)) Source #
Instance details Defined in Data.Union Associated Types type Rep (Union f (a ': as)) :: * -> * # Methods from :: Union f (a ': as) -> Rep (Union f (a ': as)) x # to :: Rep (Union f (a ': as)) x -> Union f (a ': as) #
Generic (Union f ([] :: [u])) Source #
Instance details Defined in Data.Union Associated Types type Rep (Union f []) :: * -> * # Methods from :: Union f [] -> Rep (Union f []) x # to :: Rep (Union f []) x -> Union f [] #
(f ~ Identity, Exception a, Typeable as, Exception (Union f as)) => Exception (Union f (a ': as)) Source #
Instance details Defined in Data.Union Methods toException :: Union f (a ': as) -> SomeException # fromException :: SomeException -> Maybe (Union f (a ': as)) # displayException :: Union f (a ': as) -> String #
f ~ Identity => Exception (Union f ([] :: [*])) Source #
Instance details Defined in Data.Union Methods toException :: Union f [] -> SomeException # fromException :: SomeException -> Maybe (Union f []) # displayException :: Union f [] -> String #
(NFData (f a2), NFData (Union f as)) => NFData (Union f (a2 ': as)) Source #
Instance details Defined in Data.Union Methods rnf :: Union f (a2 ': as) -> () #
NFData (Union f ([] :: [u])) Source #
Instance details Defined in Data.Union Methods rnf :: Union f [] -> () #
(Hashable (f a2), Hashable (Union f as)) => Hashable (Union f (a2 ': as)) Source #
Instance details Defined in Data.Union Methods hashWithSalt :: Int -> Union f (a2 ': as) -> Int # hash :: Union f (a2 ': as) -> Int #
Hashable (Union f ([] :: [u])) Source #
Instance details Defined in Data.Union Methods hashWithSalt :: Int -> Union f [] -> Int # hash :: Union f [] -> Int #
type Rep (Union f (a ': as)) Source #
Instance details Defined in Data.Union type Rep (Union f (a ': as)) = C1 (MetaCons "This" PrefixI False) (Rec0 (f a)) :+: C1 (MetaCons "That" PrefixI False) (Rec0 (Union f as))
type Rep (Union f ([] :: [u])) Source #
Instance details Defined in Data.Union type Rep (Union f ([] :: [u])) = (V1 :: * -> *)

union :: (Union f as -> c) -> (f a -> c) -> Union f (a ': as) -> c Source #

Case analysis for unions.

absurdUnion :: Union f '[] -> a Source #

Since a union with an empty list of labels is uninhabited, we can recover any type from it.

umap :: (forall a. f a -> g a) -> Union f as -> Union g as Source #

_This :: Prism (Union f (a ': as)) (Union f (b ': as)) (f a) (f b) Source #

_That :: Prism (Union f (a ': as)) (Union f (a ': bs)) (Union f as) (Union f bs) Source #

class i ~ RIndex a as => UElem (a :: u) (as :: [u]) (i :: Nat) where Source #

Minimal complete definition

uprism | ulift, umatch

Methods

uprism :: Prism' (Union f as) (f a) Source #

ulift :: f a -> Union f as Source #

umatch :: Union f as -> Maybe (f a) Source #

Instances

UElem (a2 :: a1) (a2 ': as :: [a1]) Z Source #
Instance details Defined in Data.Union Methods uprism :: (Choice p, Applicative f) => p (f a2) (f (f a2)) -> p (Union f (a2 ': as)) (f (Union f (a2 ': as))) Source # ulift :: f a2 -> Union f (a2 ': as) Source # umatch :: Union f (a2 ': as) -> Maybe (f a2) Source #
(RIndex a2 (b ': as) ~ S i, UElem a2 as i) => UElem (a2 :: a1) (b ': as :: [a1]) (S i) Source #
Instance details Defined in Data.Union Methods uprism :: (Choice p, Applicative f) => p (f a2) (f (f a2)) -> p (Union f (b ': as)) (f (Union f (b ': as))) Source # ulift :: f a2 -> Union f (b ': as) Source # umatch :: Union f (b ': as) -> Maybe (f a2) Source #

class is ~ RImage as bs => USubset (as :: [u]) (bs :: [u]) is where Source #

Minimal complete definition

usubset | urelax, urestrict

Methods

usubset :: Prism' (Union f bs) (Union f as) Source #

urelax :: Union f as -> Union f bs Source #

urestrict :: Union f bs -> Maybe (Union f as) Source #

Instances

USubset ([] :: [u]) (bs :: [u]) ([] :: [Nat]) Source #
Instance details Defined in Data.Union Methods usubset :: (Choice p, Applicative f) => p (Union f []) (f (Union f [])) -> p (Union f bs) (f (Union f bs)) Source # urelax :: Union f [] -> Union f bs Source # urestrict :: Union f bs -> Maybe (Union f []) Source #
(UElem a bs i, USubset as bs is) => USubset (a ': as :: [u]) (bs :: [u]) (i ': is) Source #
Instance details Defined in Data.Union Methods usubset :: (Choice p, Applicative f) => p (Union f (a ': as)) (f (Union f (a ': as))) -> p (Union f bs) (f (Union f bs)) Source # urelax :: Union f (a ': as) -> Union f bs Source # urestrict :: Union f bs -> Maybe (Union f (a ': as)) Source #

type OpenUnion = Union Identity Source #

openUnion :: forall a as. UElem a as (RIndex a as) => Prism' (OpenUnion as) a Source #