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 Symbol SymbolRepr

Methods

testEquality :: f a -> f b -> Maybe ((SymbolRepr :~: a) b)

HashableF Symbol SymbolRepr

Methods

hashWithSaltF :: Int -> f tp -> Int

hashF :: f tp -> Int

ShowF Symbol SymbolRepr

Methods

withShow :: p f -> q tp -> (Show (f tp) -> a) -> a

showF :: f tp -> String

showsF :: f tp -> String -> String

OrdF Symbol SymbolRepr

Methods

compareF :: ktp x -> ktp y -> OrderingF SymbolRepr x y

leqF :: ktp x -> ktp y -> Bool

ltF :: ktp x -> ktp y -> Bool

geqF :: ktp x -> ktp y -> Bool

gtF :: ktp x -> ktp y -> Bool

KnownSymbol s => KnownRepr Symbol SymbolRepr s

Methods

knownRepr :: s ctx

Eq (SymbolRepr x)

Methods

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

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

Ord (SymbolRepr x)

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)

Methods

showsPrec :: Int -> SymbolRepr nm -> ShowS

show :: SymbolRepr nm -> String

showList :: [SymbolRepr nm] -> ShowS

Hashable (SymbolRepr nm)

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.

Re-exports

data Symbol :: *

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

Instances

SingKind Symbol

Since: 4.9.0.0

Associated Types

type DemoteRep Symbol :: *

Methods

fromSing :: Sing Symbol a -> DemoteRep Symbol

KnownSymbol a => SingI Symbol a

Since: 4.9.0.0

Methods

sing :: Sing a a

TestEquality Symbol SymbolRepr

Methods

testEquality :: f a -> f b -> Maybe ((SymbolRepr :~: a) b)

HashableF Symbol SymbolRepr

Methods

hashWithSaltF :: Int -> f tp -> Int

hashF :: f tp -> Int

ShowF Symbol SymbolRepr

Methods

withShow :: p f -> q tp -> (Show (f tp) -> a) -> a

showF :: f tp -> String

showsF :: f tp -> String -> String

OrdF Symbol SymbolRepr

Methods

compareF :: ktp x -> ktp y -> OrderingF SymbolRepr x y

leqF :: ktp x -> ktp y -> Bool

ltF :: ktp x -> ktp y -> Bool

geqF :: ktp x -> ktp y -> Bool

gtF :: ktp x -> ktp y -> Bool

KnownSymbol n => Reifies Symbol n String

Methods

reflect :: proxy String -> a

KnownSymbol s => KnownRepr Symbol SymbolRepr s

Methods

knownRepr :: s ctx

data Sing Symbol

data Sing Symbol where

• SSym :: Sing Symbol s

type DemoteRep Symbol

type DemoteRep Symbol = String

type (==) Symbol a b

type (==) Symbol a b = EqSymbol a b

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: 4.7.0.0

Minimal complete definition

symbolSing