Safe Haskell | Safe |
---|---|
Language | Haskell98 |
- 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)
- sortPair :: Ord a => (a, a) -> (a, a)
- forcePair :: (a, b) -> (a, b)
- double :: a -> (a, a)
- fst3 :: (a, b, c) -> a
- snd3 :: (a, b, c) -> b
- thd3 :: (a, b, c) -> c
- 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)
- curry3 :: ((a, b, c) -> d) -> a -> b -> c -> d
- uncurry3 :: (a -> b -> c -> d) -> (a, b, c) -> d
- triple :: a -> (a, a, a)
Pair
mapPair :: (a -> c, b -> d) -> (a, b) -> (c, d) Source #
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.
sortPair :: Ord a => (a, a) -> (a, a) Source #
This is convenient for quick hacks but I suggest that you better define a type for an ordered pair for your application at hand. This way, you can clearly see from the type that a pair is ordered.