Generic.Data.Internal.Traversable

Generic implementation of Foldable and Traversable.

There is already a naive implementation using the generic Rep's own instances of Foldable and Traversable. However, deriving then generates a lot of code that may not be simplified away by GHC, that results in unnecessary run-time overhead.

In contrast, this implementation guarantees that the generated code is identical to stock-derived instances of Foldable and Traversable, which have the following syntactic properties:

• constructors with zero fields use pure once;
• constructors with one field use fmap once;
• constructors with n >= 2 fields use liftA2 once and (<*>) n-2 times.

The heavy lifting is actually done by the ap-normalize library.

Library

gfoldMap :: (Generic1 f, GFoldable (Rep1 f), Monoid m) => (a -> m) -> f a -> m

Generic foldMap.

instance Foldable MyTypeF where
  foldMap = gfoldMap

gtraverse :: (Generic1 f, GTraversable (Rep1 f), Applicative m) => (a -> m b) -> f a -> m (f b)

Generic traverse.

instance Traversable MyTypeF where
  traverse = gtraverse

gsequenceA :: (Generic1 f, GTraversable (Rep1 f), Applicative m) => f (m a) -> m (f a)

Generic sequenceA.

instance Traversable MyTypeF where
  sequenceA = gsequenceA

See also gtraverse.

class GFoldable_ t => GFoldable t

Class of generic representations for which Foldable can be derived.

Instances

GFoldable_ t => GFoldable t

Defined in Generic.Data.Internal.Traversable

class GTraversable_ t => GTraversable t

Class of generic representations for which Traversable can be derived.

Instances

GTraversable_ t => GTraversable t

Defined in Generic.Data.Internal.Traversable

class (GFoldMap t, Foldable t) => GFoldable_ t

Internal definition of GFoldable.

Instances

(GFoldMap t, Foldable t) => GFoldable_ t

Defined in Generic.Data.Internal.Traversable

class (GTraverse Kleisli t, GTraverse Equal t) => GTraversable_ t

Internal definition of GTraversable.

Instances

(GTraverse Kleisli t, GTraverse Equal t) => GTraversable_ t

Defined in Generic.Data.Internal.Traversable

Foldable

data Maybe' m

Isomorphic to Maybe m, but we need to micromanage the use of Monoid vs Semigroup to match exactly the output of stock deriving, for inspection testing.

Constructors

Nothing'

Just' m

type EndoM m = Endo (Maybe' m)

liftEndoM :: Monoid m => m -> EndoM m

lowerEndoM :: Monoid m => EndoM m -> m

lowerMaybe :: Monoid m => Maybe' m -> m

class GFoldMap t where

Methods

gfoldMap_ :: Monoid m => (a -> m) -> t a -> EndoM m

Instances

GFoldMap Par1

Defined in Generic.Data.Internal.Traversable

Methods

gfoldMap_ :: Monoid m => (a -> m) -> Par1 a -> EndoM m

GFoldMap (U1 :: Type -> Type)

Defined in Generic.Data.Internal.Traversable

Methods

gfoldMap_ :: Monoid m => (a -> m) -> U1 a -> EndoM m

GFoldMap (V1 :: Type -> Type)

Defined in Generic.Data.Internal.Traversable

Methods

gfoldMap_ :: Monoid m => (a -> m) -> V1 a -> EndoM m

Foldable t => GFoldMap (Rec1 t)

Defined in Generic.Data.Internal.Traversable

Methods

gfoldMap_ :: Monoid m => (a -> m) -> Rec1 t a -> EndoM m

(GFoldMap f, GFoldMap g) => GFoldMap (f :*: g)

Defined in Generic.Data.Internal.Traversable

Methods

gfoldMap_ :: Monoid m => (a -> m) -> (f :*: g) a -> EndoM m

(GFoldMap f, GFoldMap g) => GFoldMap (f :+: g)

Defined in Generic.Data.Internal.Traversable

Methods

gfoldMap_ :: Monoid m => (a -> m) -> (f :+: g) a -> EndoM m

GFoldMap (K1 i a :: Type -> Type)

Defined in Generic.Data.Internal.Traversable

Methods

gfoldMap_ :: Monoid m => (a0 -> m) -> K1 i a a0 -> EndoM m

(Foldable t, Foldable f) => GFoldMap (t :.: f)

Defined in Generic.Data.Internal.Traversable

Methods

gfoldMap_ :: Monoid m => (a -> m) -> (t :.: f) a -> EndoM m

GFoldMap f => GFoldMap (M1 i c f)

Defined in Generic.Data.Internal.Traversable

Methods

gfoldMap_ :: Monoid m => (a -> m) -> M1 i c f a -> EndoM m

Traversable

data Equal (f :: Type -> Type) a b where

Constructors

Refl :: Equal f (f b) b

Instances

GTraverse Equal Par1

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f :: Type -> Type) a b. Applicative f => Equal f a b -> Par1 a -> Aps f (Par1 b)

Traversable t => GTraverse Equal (Rec1 t)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f :: Type -> Type) a b. Applicative f => Equal f a b -> Rec1 t a -> Aps f (Rec1 t b)

(Traversable t, Traversable f) => GTraverse Equal (t :.: f)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f0 :: Type -> Type) a b. Applicative f0 => Equal f0 a b -> (t :.: f) a -> Aps f0 ((t :.: f) b)

newtype Kleisli f a b

Constructors

Kleisli (a -> f b)

Instances

GTraverse Kleisli Par1

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f :: Type -> Type) a b. Applicative f => Kleisli f a b -> Par1 a -> Aps f (Par1 b)

Traversable t => GTraverse Kleisli (Rec1 t)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f :: Type -> Type) a b. Applicative f => Kleisli f a b -> Rec1 t a -> Aps f (Rec1 t b)

(Traversable t, Traversable f) => GTraverse Kleisli (t :.: f)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f0 :: Type -> Type) a b. Applicative f0 => Kleisli f0 a b -> (t :.: f) a -> Aps f0 ((t :.: f) b)

class GTraverse arr t where

Methods

gtraverse_ :: Applicative f => arr f a b -> t a -> Aps f (t b)

Instances

GTraverse Equal Par1

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f :: Type -> Type) a b. Applicative f => Equal f a b -> Par1 a -> Aps f (Par1 b)

GTraverse Kleisli Par1

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f :: Type -> Type) a b. Applicative f => Kleisli f a b -> Par1 a -> Aps f (Par1 b)

GTraverse arr (U1 :: Type -> Type)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f :: Type -> Type) a b. Applicative f => arr f a b -> U1 a -> Aps f (U1 b)

GTraverse arr (V1 :: Type -> Type)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f :: Type -> Type) a b. Applicative f => arr f a b -> V1 a -> Aps f (V1 b)

Traversable t => GTraverse Equal (Rec1 t)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f :: Type -> Type) a b. Applicative f => Equal f a b -> Rec1 t a -> Aps f (Rec1 t b)

Traversable t => GTraverse Kleisli (Rec1 t)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f :: Type -> Type) a b. Applicative f => Kleisli f a b -> Rec1 t a -> Aps f (Rec1 t b)

(GTraverse arr f, GTraverse arr g) => GTraverse arr (f :*: g)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f0 :: Type -> Type) a b. Applicative f0 => arr f0 a b -> (f :*: g) a -> Aps f0 ((f :*: g) b)

(GTraverse arr f, GTraverse arr g) => GTraverse arr (f :+: g)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f0 :: Type -> Type) a b. Applicative f0 => arr f0 a b -> (f :+: g) a -> Aps f0 ((f :+: g) b)

GTraverse arr (K1 i a :: Type -> Type)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f :: Type -> Type) a0 b. Applicative f => arr f a0 b -> K1 i a a0 -> Aps f (K1 i a b)

(Traversable t, Traversable f) => GTraverse Equal (t :.: f)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f0 :: Type -> Type) a b. Applicative f0 => Equal f0 a b -> (t :.: f) a -> Aps f0 ((t :.: f) b)

(Traversable t, Traversable f) => GTraverse Kleisli (t :.: f)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f0 :: Type -> Type) a b. Applicative f0 => Kleisli f0 a b -> (t :.: f) a -> Aps f0 ((t :.: f) b)

GTraverse arr f => GTraverse arr (M1 i c f)

Defined in Generic.Data.Internal.Traversable

Methods

gtraverse_ :: forall (f0 :: Type -> Type) a b. Applicative f0 => arr f0 a b -> M1 i c f a -> Aps f0 (M1 i c f b)