| Copyright | (c) 2010-2011 Patrick Bahr |
|---|---|
| License | BSD3 |
| Maintainer | Patrick Bahr <paba@diku.dk> |
| Stability | experimental |
| Portability | non-portable (GHC Extensions) |
| Safe Haskell | None |
| Language | Haskell98 |
Data.Comp.Derive.Utils
Description
This module defines some utility functions for deriving instances for functor based type classes.
- abstractNewtypeQ :: Q Info -> Q Info
- abstractNewtype :: Info -> Info
- normalCon :: Con -> (Name, [StrictType])
- normalCon' :: Con -> (Name, [Type])
- normalConExp :: Con -> Q (Name, [Type])
- normalConStrExp :: Con -> Q (Name, [StrictType])
- abstractConType :: Con -> (Name, Int)
- tyVarBndrName :: TyVarBndr -> Name
- containsType :: Type -> Type -> Bool
- containsType' :: Type -> Type -> [Int]
- newNames :: Int -> String -> Q [Name]
- tupleTypes :: Int -> Int -> [Name]
- derive :: [Name -> Q [Dec]] -> [Name] -> Q [Dec]
- liftSumGen :: Name -> Name -> Name -> Q [Dec]
- findSig :: [Name] -> [Dec] -> Q (Maybe ([Name], [Name]))
Documentation
abstractNewtype :: Info -> Info Source
This function abstracts away newtype declaration, it turns them into data declarations.
normalCon :: Con -> (Name, [StrictType]) Source
This function provides the name and the arity of the given data constructor.
normalCon' :: Con -> (Name, [Type]) Source
normalConStrExp :: Con -> Q (Name, [StrictType]) Source
Same as normalConExp' but retains strictness annotations.
abstractConType :: Con -> (Name, Int) Source
This function provides the name and the arity of the given data constructor.
tyVarBndrName :: TyVarBndr -> Name Source
This function returns the name of a bound type variable
containsType :: Type -> Type -> Bool Source
containsType' :: Type -> Type -> [Int] Source
newNames :: Int -> String -> Q [Name] Source
This function provides a list (of the given length) of new names based on the given string.
tupleTypes :: Int -> Int -> [Name] Source
derive :: [Name -> Q [Dec]] -> [Name] -> Q [Dec] Source
Helper function for generating a list of instances for a list of named signatures. For example, in order to derive instances Functor and ShowF for a signature Exp, use derive as follows (requires Template Haskell):
$(derive [makeFunctor, makeShowF] [''Exp])
liftSumGen :: Name -> Name -> Name -> Q [Dec] Source
This function lifts type class instances over sums ofsignatures. To this end it assumes that it contains only methods with types of the form f t1 .. tn -> t where f is the signature that is used to construct sums. Since this function is generic it assumes as its first argument the name of the function that is used to lift methods over sums i.e. a function of type
(f t1 .. tn -> t) -> (g t1 .. tn -> t) -> ((f :+: g) t1 .. tn -> t)
where :+: is the sum type constructor. The second argument to this function is expected to be the name of that constructor. The last argument is the name of the class whose instances should be lifted over sums.