utility-ht-0.0.14: 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)
- zipWithPair :: (a -> c -> e, b -> d -> f) -> (a, b) -> (c, d) -> (e, f)
- 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)
- zipWithTriple :: (a -> d -> g, b -> e -> h, c -> f -> i) -> (a, b, c) -> (d, e, f) -> (g, h, i)
- 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`

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

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) #

zipWithTriple :: (a -> d -> g, b -> e -> h, c -> f -> i) -> (a, b, c) -> (d, e, f) -> (g, h, i) #

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