Data.LargeHashable.TH

Documentation

deriveLargeHashable :: Name -> Q [Dec]

Template Haskell function to automatically derive instances of LargeHashable. The derived instances first calls updateHash with an unique identifier number for every constructor, followed by updateHash calls for every field of the constructor (if existent). It also works for type families.

E. g. for the following code

data BlaFoo a = Foo
              | Bar Int a
              | Baz a a

$(deriveLargeHashable ''BlaFoo)
  

The following instance gets generated:

instance LargeHashable a_apg8 =>
        LargeHashable (BlaFoo a_apg8) where
 updateHash Foo = updateHash (0 :: Foreign.C.Types.CULong)
 updateHash (Bar a b)
   = (((updateHash (1 :: Foreign.C.Types.CULong)) >> (updateHash a))
      >> (updateHash b))
 updateHash (XY a b)
   = (((updateHash (2 :: Foreign.C.Types.CULong)) >> (updateHash a))
      >> (updateHash b))
   

deriveLargeHashableCtx

Arguments

:: Name

-> ([TypeQ] -> [PredQ])

Function mapping the type variables in the instance head to the additional constraints

-> Q [Dec]

Derive a LargeHashable instance with extra constraints in the context of the instance.

deriveLargeHashableNoCtx :: Name -> Q [Dec]

Derive a LargeHashable instance with no constraints in the context of the instance.

deriveLargeHashableCustomCtx

Arguments

:: Name

-> ([TypeQ] -> [PredQ] -> [PredQ])

Function mapping the type variables in the instance head and the constraints that would normally be generated to the constraints that should be generated.

-> Q [Dec]

Derive a LargeHashable instance with a completely custom instance context.