Data.Aeson.Schema.Utils.Sum

The SumType data type that represents a sum type consisting of types specified in a type-level list.

Documentation

data SumType (types :: [Type]) where

Represents a sum type.

Loads the first type that successfully parses the JSON value.

Example:

data Owl = Owl
data Cat = Cat
data Toad = Toad
type Animal = SumType '[Owl, Cat, Toad]

Here Owl                         :: Animal
There (Here Cat)                 :: Animal
There (There (Here Toad))        :: Animal

{- Fails at compile-time
Here True                        :: Animal
Here Cat                         :: Animal
There (Here Owl)                 :: Animal
There (There (There (Here Owl))) :: Animal
-}

Constructors

Here :: forall x xs. x -> SumType (x ': xs)

There :: forall x xs. SumType xs -> SumType (x ': xs)

Instances

(Eq x, Eq (SumType xs)) => Eq (SumType (x ': xs))

Defined in Data.Aeson.Schema.Utils.Sum

Methods

(==) :: SumType (x ': xs) -> SumType (x ': xs) -> Bool

(/=) :: SumType (x ': xs) -> SumType (x ': xs) -> Bool

Eq (SumType ([] :: [Type]))

Defined in Data.Aeson.Schema.Utils.Sum

Methods

(==) :: SumType [] -> SumType [] -> Bool

(/=) :: SumType [] -> SumType [] -> Bool

(Ord x, Ord (SumType xs)) => Ord (SumType (x ': xs))

Defined in Data.Aeson.Schema.Utils.Sum

Methods

compare :: SumType (x ': xs) -> SumType (x ': xs) -> Ordering

(<) :: SumType (x ': xs) -> SumType (x ': xs) -> Bool

(<=) :: SumType (x ': xs) -> SumType (x ': xs) -> Bool

(>) :: SumType (x ': xs) -> SumType (x ': xs) -> Bool

(>=) :: SumType (x ': xs) -> SumType (x ': xs) -> Bool

max :: SumType (x ': xs) -> SumType (x ': xs) -> SumType (x ': xs)

min :: SumType (x ': xs) -> SumType (x ': xs) -> SumType (x ': xs)

Ord (SumType ([] :: [Type]))

Defined in Data.Aeson.Schema.Utils.Sum

Methods

compare :: SumType [] -> SumType [] -> Ordering

(<) :: SumType [] -> SumType [] -> Bool

(<=) :: SumType [] -> SumType [] -> Bool

(>) :: SumType [] -> SumType [] -> Bool

(>=) :: SumType [] -> SumType [] -> Bool

max :: SumType [] -> SumType [] -> SumType []

min :: SumType [] -> SumType [] -> SumType []

(Show x, Show (SumType xs)) => Show (SumType (x ': xs))

Defined in Data.Aeson.Schema.Utils.Sum

Methods

showsPrec :: Int -> SumType (x ': xs) -> ShowS

show :: SumType (x ': xs) -> String

showList :: [SumType (x ': xs)] -> ShowS

Show (SumType ([] :: [Type]))

Defined in Data.Aeson.Schema.Utils.Sum

Methods

showsPrec :: Int -> SumType [] -> ShowS

show :: SumType [] -> String

showList :: [SumType []] -> ShowS

(FromJSON x, FromJSON (SumType xs)) => FromJSON (SumType (x ': xs))

Defined in Data.Aeson.Schema.Utils.Sum

Methods

parseJSON :: Value -> Parser (SumType (x ': xs))

parseJSONList :: Value -> Parser [SumType (x ': xs)]

FromJSON (SumType ([] :: [Type]))

Defined in Data.Aeson.Schema.Utils.Sum

Methods

parseJSON :: Value -> Parser (SumType [])

parseJSONList :: Value -> Parser [SumType []]

fromSumType :: (IsInRange n types, Just result ~ GetIndex n types, FromSumType n types result) => proxy n -> SumType types -> Maybe result

Extract a value from a SumType

Example:

type Animal = SumType '[Owl, Cat, Toad]
let someAnimal = ... :: Animal

fromSumType (Proxy :: Proxy 0) someAnimal :: Maybe Owl
fromSumType (Proxy :: Proxy 1) someAnimal :: Maybe Cat
fromSumType (Proxy :: Proxy 2) someAnimal :: Maybe Toad

-- Compile-time error
-- fromSumType (Proxy :: Proxy 3) someAnimal