Data.Barbie.Internal.Traversable

Documentation

class FunctorB b => TraversableB b where

Barbie-types that can be traversed from left to right. Instances should satisfy the following laws:

 t . btraverse f = btraverse (t . f)  -- naturality
btraverse Identity = Identity         -- identity
btraverse (Compose . fmap g . f) = Compose . fmap (btraverse g) . btraverse f -- composition

There is a default btraverse implementation for Generic types, so instances can derived automatically.

Methods

btraverse :: Applicative t => (forall a. f a -> t (g a)) -> b f -> t (b g)

btraverse :: (Applicative t, CanDeriveGenericInstance b) => (forall a. f a -> t (g a)) -> b f -> t (b g)

Instances

TraversableB b => TraversableB (Barbie b)

Methods

btraverse :: Applicative t => (forall a. f a -> t (g a)) -> Barbie b f -> t (Barbie b g)

bsequence :: (Applicative f, TraversableB b) => b (Compose f g) -> f (b g)

Evaluate each action in the structure from left to right, and collect the results.

type CanDeriveGenericInstance b = (Generic (b (Target F)), Generic (b (Target G)), GTraversableB (Rep (b (Target F))), Rep (b (Target G)) ~ Repl (Target F) (Target G) (Rep (b (Target F))))

Intuivively, the requirements to have TraversableB B derived are:

• There is an instance of Generic (B f) for every f
• If f is used as argument to some type in the definition of B, it is only on a Barbie-type with a TraversableB instance.
• Recursive usages of B f are allowed to appear as argument to a Traversable (e.g. @Maybe (B f)')

class GTraversableB b

Minimal complete definition

gbtraverse

Instances

GTraversableB (V1 *)

Methods

gbtraverse :: Applicative t => (forall a. f a -> t (g a)) -> V1 * x -> t (Repl (Target F) (Target G) (V1 *) x)

GTraversableB (U1 *)

Methods

gbtraverse :: Applicative t => (forall a. f a -> t (g a)) -> U1 * x -> t (Repl (Target F) (Target G) (U1 *) x)

(~) (* -> *) (K1 * i c) (Repl (Target F) (Target G) (K1 * i c)) => GTraversableB (K1 * i c)

Methods

gbtraverse :: Applicative t => (forall a. f a -> t (g a)) -> K1 * i c x -> t (Repl (Target F) (Target G) (K1 * i c) x)

(GTraversableB l, GTraversableB r) => GTraversableB ((:+:) * l r)

Methods

gbtraverse :: Applicative t => (forall a. f a -> t (g a)) -> (* :+: l) r x -> t (Repl (Target F) (Target G) ((* :+: l) r) x)

(GTraversableB l, GTraversableB r) => GTraversableB ((:*:) * l r)

Methods

gbtraverse :: Applicative t => (forall a. f a -> t (g a)) -> (* :*: l) r x -> t (Repl (Target F) (Target G) ((* :*: l) r) x)

GTraversableB x => GTraversableB (M1 * i c x)

Methods

gbtraverse :: Applicative t => (forall a. f a -> t (g a)) -> M1 * i c x x -> t (Repl (Target F) (Target G) (M1 * i c x) x)

gbtraverseDefault :: (Applicative t, CanDeriveGenericInstance b) => (forall a. f a -> t (g a)) -> b f -> t (b g)

Default implementation of btraverse based on Generic.