Haskell Hierarchical Libraries (base package) Contents Index

Data.Generics.Twins Portability non-portable Stability experimental Maintainer libraries@haskell.org

Contents The idiom of multi-parameter traversal Twin mapping combinators Prime examples of twin traversal

Description

"Scrap your boilerplate" --- Generic programming in Haskell See http://www.cs.vu.nl/boilerplate/. The present module provides support for multi-parameter traversal, which is also demonstrated with generic operations like equality.

Synopsis

tfoldl :: (forall a b . Data a => c (a -> b) -> c a -> c b) -> (forall g . g -> c g) -> GenericQ (Generic c) -> GenericQ (Generic c) tmapT :: GenericQ GenericT -> GenericQ GenericT tmapQl :: (r -> r -> r) -> r -> GenericQ (GenericQ r) -> GenericQ (GenericQ r) tmapM :: Monad m => GenericQ (GenericM m) -> GenericQ (GenericM m) geq :: Data a => a -> a -> Bool gzip :: (forall a b . (Data a, Data b) => a -> b -> Maybe b) -> forall a b . (Data a, Data b) => a -> b -> Maybe b

The idiom of multi-parameter traversal

tfoldl :: (forall a b . Data a => c (a -> b) -> c a -> c b) -> (forall g . g -> c g) -> GenericQ (Generic c) -> GenericQ (Generic c)

Twin mapping combinators

tmapT :: GenericQ GenericT -> GenericQ GenericT

tmapQl :: (r -> r -> r) -> r -> GenericQ (GenericQ r) -> GenericQ (GenericQ r)

tmapM :: Monad m => GenericQ (GenericM m) -> GenericQ (GenericM m)

Prime examples of twin traversal

geq :: Data a => a -> a -> Bool

Generic equality: an alternative to "deriving Eq"

gzip :: (forall a b . (Data a, Data b) => a -> b -> Maybe b) -> forall a b . (Data a, Data b) => a -> b -> Maybe b

Generic zip controlled by a function with type-specific branches

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