Data.Parameterized.SymbolRepr

This defines a type family SymbolRepr for representing a type-level string (AKA symbol) at runtime. This can be used to branch on a type-level value.

The TestEquality and OrdF instances for SymbolRepr are implemented using unsafeCoerce. This should be typesafe because we maintain the invariant that the string value contained in a SymbolRepr value matches its static type.

At the type level, symbols have very few operations, so SymbolRepr correspondingly has very few functions that manipulate them.

SymbolRepr

data SymbolRepr (nm :: Symbol)

A runtime representation of a GHC type-level symbol.

Instances

TestEquality SymbolRepr

Defined in Data.Parameterized.SymbolRepr

Methods

testEquality :: forall (a :: k) (b :: k). SymbolRepr a -> SymbolRepr b -> Maybe (a :~: b)

HashableF SymbolRepr

Defined in Data.Parameterized.SymbolRepr

Methods

hashWithSaltF :: forall (tp :: k). Int -> SymbolRepr tp -> Int

hashF :: forall (tp :: k). SymbolRepr tp -> Int

ShowF SymbolRepr

Defined in Data.Parameterized.SymbolRepr

Methods

withShow :: forall p q (tp :: k) a. p SymbolRepr -> q tp -> (Show (SymbolRepr tp) => a) -> a

showF :: forall (tp :: k). SymbolRepr tp -> String

showsPrecF :: forall (tp :: k). Int -> SymbolRepr tp -> String -> String

OrdF SymbolRepr

Defined in Data.Parameterized.SymbolRepr

Methods

compareF :: forall (x :: k) (y :: k). SymbolRepr x -> SymbolRepr y -> OrderingF x y

leqF :: forall (x :: k) (y :: k). SymbolRepr x -> SymbolRepr y -> Bool

ltF :: forall (x :: k) (y :: k). SymbolRepr x -> SymbolRepr y -> Bool

geqF :: forall (x :: k) (y :: k). SymbolRepr x -> SymbolRepr y -> Bool

gtF :: forall (x :: k) (y :: k). SymbolRepr x -> SymbolRepr y -> Bool

IsRepr SymbolRepr

Defined in Data.Parameterized.WithRepr

Methods

withRepr :: forall (a :: k) r. SymbolRepr a -> (KnownRepr SymbolRepr a => r) -> r

KnownSymbol s => KnownRepr SymbolRepr (s :: Symbol)

Defined in Data.Parameterized.SymbolRepr

Methods

knownRepr :: SymbolRepr s

Eq (SymbolRepr x)

Defined in Data.Parameterized.SymbolRepr

Methods

(==) :: SymbolRepr x -> SymbolRepr x -> Bool

(/=) :: SymbolRepr x -> SymbolRepr x -> Bool

Ord (SymbolRepr x)

Defined in Data.Parameterized.SymbolRepr

Methods

compare :: SymbolRepr x -> SymbolRepr x -> Ordering

(<) :: SymbolRepr x -> SymbolRepr x -> Bool

(<=) :: SymbolRepr x -> SymbolRepr x -> Bool

(>) :: SymbolRepr x -> SymbolRepr x -> Bool

(>=) :: SymbolRepr x -> SymbolRepr x -> Bool

max :: SymbolRepr x -> SymbolRepr x -> SymbolRepr x

min :: SymbolRepr x -> SymbolRepr x -> SymbolRepr x

Show (SymbolRepr nm)

Defined in Data.Parameterized.SymbolRepr

Methods

showsPrec :: Int -> SymbolRepr nm -> ShowS

show :: SymbolRepr nm -> String

showList :: [SymbolRepr nm] -> ShowS

Hashable (SymbolRepr nm)

Defined in Data.Parameterized.SymbolRepr

Methods

hashWithSalt :: Int -> SymbolRepr nm -> Int

hash :: SymbolRepr nm -> Int

symbolRepr :: SymbolRepr nm -> Text

The underlying text representation of the symbol

knownSymbol :: KnownSymbol s => SymbolRepr s

Generate a value representative for the type level symbol.

someSymbol :: Text -> Some SymbolRepr

Generate a symbol representative at runtime. The type-level symbol will be abstract, as it is hidden by the Some constructor.

data SomeSym (c :: Symbol -> Type)

The SomeSym hides a Symbol parameter but preserves a KnownSymbol constraint on the hidden parameter.

Constructors

forall (s :: Symbol).KnownSymbol s => SomeSym (c s)

viewSomeSym :: (forall (s :: Symbol). KnownSymbol s => c s -> r) -> SomeSym c -> r

Projects a value out of a SomeSym into a function, re-ifying the Symbol type parameter to the called function, along with the KnownSymbol constraint on that Symbol value.

Re-exports

data Symbol

(Kind) This is the kind of type-level symbols. Declared here because class IP needs it

Instances

SingKind Symbol

Since: base-4.9.0.0

Defined in GHC.Generics

Associated Types

type DemoteRep Symbol

Methods

fromSing :: forall (a :: Symbol). Sing a -> DemoteRep Symbol

TestEquality SymbolRepr

Defined in Data.Parameterized.SymbolRepr

Methods

testEquality :: forall (a :: k) (b :: k). SymbolRepr a -> SymbolRepr b -> Maybe (a :~: b)

HashableF SymbolRepr

Defined in Data.Parameterized.SymbolRepr

Methods

hashWithSaltF :: forall (tp :: k). Int -> SymbolRepr tp -> Int

hashF :: forall (tp :: k). SymbolRepr tp -> Int

ShowF SymbolRepr

Defined in Data.Parameterized.SymbolRepr

Methods

withShow :: forall p q (tp :: k) a. p SymbolRepr -> q tp -> (Show (SymbolRepr tp) => a) -> a

showF :: forall (tp :: k). SymbolRepr tp -> String

showsPrecF :: forall (tp :: k). Int -> SymbolRepr tp -> String -> String

OrdF SymbolRepr

Defined in Data.Parameterized.SymbolRepr

Methods

compareF :: forall (x :: k) (y :: k). SymbolRepr x -> SymbolRepr y -> OrderingF x y

leqF :: forall (x :: k) (y :: k). SymbolRepr x -> SymbolRepr y -> Bool

ltF :: forall (x :: k) (y :: k). SymbolRepr x -> SymbolRepr y -> Bool

geqF :: forall (x :: k) (y :: k). SymbolRepr x -> SymbolRepr y -> Bool

gtF :: forall (x :: k) (y :: k). SymbolRepr x -> SymbolRepr y -> Bool

KnownSymbol a => SingI (a :: Symbol)

Since: base-4.9.0.0

Defined in GHC.Generics

Methods

sing :: Sing a

IsRepr SymbolRepr

Defined in Data.Parameterized.WithRepr

Methods

withRepr :: forall (a :: k) r. SymbolRepr a -> (KnownRepr SymbolRepr a => r) -> r

KnownSymbol n => Reifies (n :: Symbol) String

Defined in Data.Reflection

Methods

reflect :: proxy n -> String

KnownSymbol s => KnownRepr SymbolRepr (s :: Symbol)

Defined in Data.Parameterized.SymbolRepr

Methods

knownRepr :: SymbolRepr s

type DemoteRep Symbol

Defined in GHC.Generics

type DemoteRep Symbol = String

data Sing (s :: Symbol)

Defined in GHC.Generics

data Sing (s :: Symbol) where

• SSym :: forall (s :: Symbol). KnownSymbol s => Sing s

class KnownSymbol (n :: Symbol)

This class gives the string associated with a type-level symbol. There are instances of the class for every concrete literal: "hello", etc.

Since: base-4.7.0.0

Minimal complete definition

symbolSing