Data.Generics.Twins

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

Generic folds and maps that also accumulate

gfoldlAccum :: Data d => (forall e r. Data e => a -> c (e -> r) -> e -> (a, c r)) -> (forall g. a -> g -> (a, c g)) -> a -> d -> (a, c d)

gfoldl with accumulation

gmapAccumT :: Data d => (forall e. Data e => a -> e -> (a, e)) -> a -> d -> (a, d)

gmapT with accumulation

gmapAccumM :: (Data d, Monad m) => (forall e. Data e => a -> e -> (a, m e)) -> a -> d -> (a, m d)

gmapM with accumulation

gmapAccumQl :: Data d => (r -> r' -> r) -> r -> (forall e. Data e => a -> e -> (a, r')) -> a -> d -> (a, r)

gmapQl with accumulation

gmapAccumQr :: Data d => (r' -> r -> r) -> r -> (forall e. Data e => a -> e -> (a, r')) -> a -> d -> (a, r)

gmapQr with accumulation

gmapAccumQ :: Data d => (forall e. Data e => a -> e -> (a, q)) -> a -> d -> (a, [q])

gmapQ with accumulation

gmapAccumA :: forall b d a. (Data d, Applicative a) => (forall e. Data e => b -> e -> (b, a e)) -> b -> d -> (b, a d)

Applicative version

Mapping combinators for twin traversal

gzipWithT :: GenericQ GenericT -> GenericQ GenericT

Twin map for transformation

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

Twin map for monadic transformation

gzipWithQ :: GenericQ (GenericQ r) -> GenericQ (GenericQ [r])

Twin map for queries

Typical twin traversals

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

Generic equality: an alternative to "deriving Eq"

gzip :: GenericQ (GenericM Maybe) -> GenericQ (GenericM Maybe)

Generic zip controlled by a function with type-specific branches

gcompare :: Data a => a -> a -> Ordering

Generic comparison: an alternative to "deriving Ord"