Data.Generics.Schemes

"Scrap your boilerplate" --- Generic programming in Haskell See http://www.cs.uu.nl/wiki/GenericProgramming/SYB. The present module provides frequently used generic traversal schemes.

Documentation

everywhere :: (forall a. Data a => a -> a) -> forall a. Data a => a -> a

Apply a transformation everywhere in bottom-up manner

everywhere' :: (forall a. Data a => a -> a) -> forall a. Data a => a -> a

Apply a transformation everywhere in top-down manner

everywhereBut :: GenericQ Bool -> GenericT -> GenericT

Variation on everywhere with an extra stop condition

everywhereM :: Monad m => GenericM m -> GenericM m

Monadic variation on everywhere

somewhere :: MonadPlus m => GenericM m -> GenericM m

Apply a monadic transformation at least somewhere

everything :: (r -> r -> r) -> GenericQ r -> GenericQ r

Summarise all nodes in top-down, left-to-right order

everythingBut :: (r -> r -> r) -> GenericQ (r, Bool) -> GenericQ r

Variation of "everything" with an added stop condition

everythingWithContext :: s -> (r -> r -> r) -> GenericQ (s -> (r, s)) -> GenericQ r

Summarise all nodes in top-down, left-to-right order, carrying some state down the tree during the computation, but not left-to-right to siblings.

listify :: Typeable r => (r -> Bool) -> GenericQ [r]

Get a list of all entities that meet a predicate

something :: GenericQ (Maybe u) -> GenericQ (Maybe u)

Look up a subterm by means of a maybe-typed filter

synthesize :: s -> (t -> s -> s) -> GenericQ (s -> t) -> GenericQ t

Bottom-up synthesis of a data structure; 1st argument z is the initial element for the synthesis; 2nd argument o is for reduction of results from subterms; 3rd argument f updates the synthesised data according to the given term

gsize :: Data a => a -> Int

Compute size of an arbitrary data structure

glength :: GenericQ Int

Count the number of immediate subterms of the given term

gdepth :: GenericQ Int

Determine depth of the given term

gcount :: GenericQ Bool -> GenericQ Int

Determine the number of all suitable nodes in a given term

gnodecount :: GenericQ Int

Determine the number of all nodes in a given term

gtypecount :: Typeable a => a -> GenericQ Int

Determine the number of nodes of a given type in a given term

gfindtype :: (Data x, Typeable y) => x -> Maybe y

Find (unambiguously) an immediate subterm of a given type