Symbol package:constraints

module Data.Constraint.Symbol
constraints
Utilities for working with KnownSymbol constraints.
type family AppendSymbol (a :: Symbol) (b :: Symbol) :: Symbol
constraints Data.Constraint.Symbol
Concatenation of type-level symbols.
appendSymbol :: (KnownSymbol a, KnownSymbol b) :- KnownSymbol (AppendSymbol a b)
constraints Data.Constraint.Symbol
dropSymbol :: forall n a . (KnownNat n, KnownSymbol a) :- KnownSymbol (Drop n a)
constraints Data.Constraint.Symbol
lengthSymbol :: forall a . KnownSymbol a :- KnownNat (Length a)
constraints Data.Constraint.Symbol
takeSymbol :: forall n a . (KnownNat n, KnownSymbol a) :- KnownSymbol (Take n a)
constraints Data.Constraint.Symbol
unsafeSSymbol :: String -> SSymbol s
constraints Data.Constraint.Unsafe
Unsafely create an SSymbol value directly from a String. Use this function with care:
  • The String value must match the Symbol s encoded in the return type SSymbol s.
  • Be wary of using this function to create multiple values of type SSymbol T, where T is a type family that does not reduce (e.g., Any from GHC.Exts). If you do, GHC is liable to optimize away one of the values and replace it with the other during a common subexpression elimination pass. If the two values have different underlying String values, this could be disastrous.