| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Data.Generics.Traversable
Description
All of the functions below work only on «interesting» subterms.
It is up to the instance writer to decide which subterms are
interesting and which subterms should count as immediate. This can
also depend on the context c.
The context, denoted c, is a constraint (of kind * -> Constraint)
that provides additional facilities to work with the data.
In most cases, the context cannot be inferred automatically.
You need to provide it using the
type application syntax:
gmap @Show f x everywhere @Typeable f x
etc.
For more information, see:
- Scrap your boilerplate with class
- https://www.microsoft.com/en-us/research/publication/scrap-your-boilerplate-with-class/
- Generalizing generic fold
- http://ro-che.info/articles/2013-03-11-generalizing-gfoldl
- class GTraversable c a where
- gmap :: forall c a. GTraversable c a => (forall d. c d => d -> d) -> a -> a
- gmapM :: forall c m a. (Monad m, GTraversable c a) => (forall d. c d => d -> m d) -> a -> m a
- gfoldMap :: forall c r a. (Monoid r, GTraversable c a) => (forall d. c d => d -> r) -> a -> r
- gfoldr :: forall c a r. GTraversable c a => (forall d. c d => d -> r -> r) -> r -> a -> r
- gfoldl' :: forall c a r. GTraversable c a => (forall d. c d => r -> d -> r) -> r -> a -> r
- class (GTraversable (Rec c) a, c a) => Rec c a
- everywhere :: forall c a. Rec c a => (forall d. Rec c d => d -> d) -> a -> a
- everywhere' :: forall c a. Rec c a => (forall d. Rec c d => d -> d) -> a -> a
- everywhereM :: forall c m a. (Monad m, Rec c a) => (forall d. Rec c d => d -> m d) -> a -> m a
- everything :: forall c r a. Rec c a => (r -> r -> r) -> (forall d. Rec c d => d -> r) -> a -> r
Open recursion combinators
class GTraversable c a where Source #
Methods
gtraverse :: Applicative f => (forall d. c d => d -> f d) -> a -> f a Source #
Applicative traversal over (a subset of) immediate subterms. This is
a generic version of traverse.
The supplied function is applied only to the «interesting» subterms.
Other subterms are lifted using pure, and the whole structure is
folded back using <*>.
gtraverse has a default implementation const pure, which works for
types without interesting subterms (in particular, atomic types).
gmap :: forall c a. GTraversable c a => (forall d. c d => d -> d) -> a -> a Source #
Generic map over the immediate subterms
gmapM :: forall c m a. (Monad m, GTraversable c a) => (forall d. c d => d -> m d) -> a -> m a Source #
Generic monadic map over the immediate subterms
gfoldMap :: forall c r a. (Monoid r, GTraversable c a) => (forall d. c d => d -> r) -> a -> r Source #
Generic monoidal fold over the immediate subterms (cf. foldMap)
gfoldr :: forall c a r. GTraversable c a => (forall d. c d => d -> r -> r) -> r -> a -> r Source #
Generic right fold over the immediate subterms
gfoldl' :: forall c a r. GTraversable c a => (forall d. c d => r -> d -> r) -> r -> a -> r Source #
Generic strict left fold over the immediate subterms
Closed recursion combinators
class (GTraversable (Rec c) a, c a) => Rec c a Source #
Rec enables "deep traversals".
It is satisfied automatically when its superclass constraints are satisfied — you are not supposed to declare new instances of this class.
Instances
| (GTraversable (Rec c) a, c a) => Rec c a Source # | |
everywhere :: forall c a. Rec c a => (forall d. Rec c d => d -> d) -> a -> a Source #
Apply a transformation everywhere in bottom-up manner
everywhere' :: forall c a. Rec c a => (forall d. Rec c d => d -> d) -> a -> a Source #
Apply a transformation everywhere in top-down manner
everywhereM :: forall c m a. (Monad m, Rec c a) => (forall d. Rec c d => d -> m d) -> a -> m a Source #
Monadic variation on everywhere
everything :: forall c r a. Rec c a => (r -> r -> r) -> (forall d. Rec c d => d -> r) -> a -> r Source #
Strict left fold over all elements, top-down