genifunctors-0.4: Generate generalized fmap, foldMap and traverse

Data.Generics.Genifunctors

Description

Generate (derive) generalized fmap, foldMap and traverse for Bifunctors, Trifunctors, or a functor with any arity

Example:

data U a b c d
= L [U a b c d]               -- polymorphic recursion
| M (V (a,b) (Either c d))    -- mutually recursive
| a :+: Int                   -- infix syntax, record syntax, type synonyms
| R { c :: c, d :: String }   -- and primitive data types supported

data V u v = X (U v v u u) | Z u

fmapU :: (a -> a') -> (b -> b') -> (c -> c') -> (d -> d') -> U a b c d -> U a' b' c' d'
fmapU = $(genFmap ''U) foldU :: Monoid m => (a -> m) -> (b -> m) -> (c -> m) -> (d -> m) -> U a b c d -> m foldU =$(genFoldMap ''U)

travU :: Applicative f => (a -> f a') -> (b -> f b') -> (c -> f c') -> (d -> f d') -> U a b c d -> f (U a' b' c' d')
travU = $(genTraverse ''U)  genFoldMapT and genTraverseT allow for specifying custom functions to handle subparts of a specific type. The compiler will throw an error if any of the types is actually a type synonym. Synopsis # Documentation Generate generalized fmap for a type bimapTuple :: (a -> a') -> (b -> b') -> (a,b) -> (a',b') bimapTuple =$(genFmap ''(,))


Generate generalized foldMap for a type

foldMapEither :: Monoid m => (a -> m) -> (b -> m) -> Either a b -> m
foldMapEither = $(genFoldMap ''Either)  genFoldMapT :: [(Name, Name)] -> Name -> Q Exp Source # Generate generalized foldMap for a type, optionally traversing subparts of it with custom implementations. foldTupleRev :: Monoid m => (a -> m) -> (b -> m) -> (a,b) -> m foldTupleRev f g (a,b) = g b <> f a foldUCustom :: Monoid m => (a -> m) -> (b -> m) -> (c -> m) -> (d -> m) -> U a b c d -> m foldUCustom =$(genFoldMapT [(''(,), 'foldTupleRev)] ''U)


Generate generalized traversable for a type

travTriple :: Applicative f => (a -> f a') -> (b -> f b') -> (c -> f c') -> (a,b,c) -> f (a',b',c')
travTriple = $(genTraverse ''(,,))  genTraverseT :: [(Name, Name)] -> Name -> Q Exp Source # Generate generalized traversable for a type, optionally traversing subparts of it with custom implementations. travTupleRev :: Applicative f => (a -> f a') -> (b -> f b') -> (a,b) -> f (a',b') travTupleRev f g (a,b) = (\b a -> (a,b)) <$> g b <*> f a

travUCustom :: Applicative f => (a -> f a') -> (b -> f b') -> (c -> f c') -> (d -> f d') -> U a b c d -> f (U a' b' c' d')
travUCustom = $(genTraverseT [(''(,), 'travTupleRev), (''V, 'travVCustom)] ''U) travVCustom :: Applicative f => (a -> f a') -> (b -> f b') -> V a b -> f (V a' b') travVCustom =$(genTraverseT [(''U, 'travUCustom)] ''V)