| Copyright | (c) Galois Inc 2014-2019 |
|---|---|
| Maintainer | Joe Hendrix <jhendrix@galois.com> |
| Safe Haskell | Trustworthy |
| Language | Haskell2010 |
Data.Parameterized.SymbolRepr
Contents
Description
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.
Synopsis
- data SymbolRepr (nm :: Symbol)
- symbolRepr :: SymbolRepr nm -> Text
- knownSymbol :: KnownSymbol s => SymbolRepr s
- someSymbol :: Text -> Some SymbolRepr
- data SomeSym (c :: Symbol -> Type) = forall (s :: Symbol).KnownSymbol s => SomeSym (c s)
- viewSomeSym :: (forall (s :: Symbol). KnownSymbol s => c s -> r) -> SomeSym c -> r
- data Symbol
- class KnownSymbol (n :: Symbol)
SymbolRepr
data SymbolRepr (nm :: Symbol) Source #
A runtime representation of a GHC type-level symbol.
Instances
symbolRepr :: SymbolRepr nm -> Text Source #
The underlying text representation of the symbol
knownSymbol :: KnownSymbol s => SymbolRepr s Source #
Generate a value representative for the type level symbol.
someSymbol :: Text -> Some SymbolRepr Source #
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) Source #
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 Source #
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
(Kind) This is the kind of type-level symbols. Declared here because class IP needs it
Instances
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