Data.Tuple.Lazy

utility-ht-0.0.11: Various small helper functions for Lists, Maybes, Tuples, Functions

Safe Haskell | Safe
Language | Haskell98

Data.Tuple.Lazy

Contents

- Pair
- Triple

Synopsis

- mapPair :: (a -> c, b -> d) -> (a, b) -> (c, d)
- mapFst :: (a -> c) -> (a, b) -> (c, b)
- mapSnd :: (b -> c) -> (a, b) -> (a, c)
- swap :: (a, b) -> (b, a)
- forcePair :: (a, b) -> (a, b)
- mapTriple :: (a -> d, b -> e, c -> f) -> (a, b, c) -> (d, e, f)
- mapFst3 :: (a -> d) -> (a, b, c) -> (d, b, c)
- mapSnd3 :: (b -> d) -> (a, b, c) -> (a, d, c)
- mapThd3 :: (c -> d) -> (a, b, c) -> (a, b, d)
- uncurry3 :: (a -> b -> c -> d) -> (a, b, c) -> d

# Pair

mapPair :: (a -> c, b -> d) -> (a, b) -> (c, d)

Cf. '(Control.Arrow.***)'.

Apply two functions on corresponding values in a pair, where the pattern match on the pair constructor is lazy. This is crucial in recursions such as the one of `partition`. One the other hand there are applications where strict application is crucial, e.g. `mapSnd f ab` where the left pair member is a large lazy list. With the lazy `mapSnd` we make the application of `f` depend on the whole pair `ab`. See Data.Tuple.Example for two examples where one variant is definitely better than the other one.

mapFst :: (a -> c) -> (a, b) -> (c, b)

`first`

mapSnd :: (b -> c) -> (a, b) -> (a, c)

`second`

swap :: (a, b) -> (b, a)

forcePair :: (a, b) -> (a, b)

# Triple

mapTriple :: (a -> d, b -> e, c -> f) -> (a, b, c) -> (d, e, f)

mapFst3 :: (a -> d) -> (a, b, c) -> (d, b, c)

mapSnd3 :: (b -> d) -> (a, b, c) -> (a, d, c)

mapThd3 :: (c -> d) -> (a, b, c) -> (a, b, d)

uncurry3 :: (a -> b -> c -> d) -> (a, b, c) -> d