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  1. data IntMap a

    relude Relude.Container.Reexport

    A map of integers to values a.

  2. inverseMap :: (Bounded a, Enum a, Ord k) => (a -> k) -> k -> Maybe a

    relude Relude.Enum

    inverseMap f creates a function that is the inverse of a given function f. It does so by constructing Map internally for each value f a. The implementation makes sure that the Map is constructed only once and then shared for every call. Memory usage note: don't inverse functions that have types like Int as their input. In this case the created Map will have huge size. The complexity of reversed mapping is <math>. Performance note: make sure to specialize monomorphic type of your functions that use inverseMap to avoid Map reconstruction. One of the common inverseMap use-case is inverting the show or a show-like function. 

    >>> data Color = Red | Green | Blue deriving (Show, Enum, Bounded)

>>> parse = inverseMap show :: String -> Maybe Color

>>> parse "Red"
Just Red

>>> parse "Black"
Nothing
    Correctness note: inverseMap expects injective function as its argument, i.e. the function must map distinct arguments to distinct values. Typical usage of this function looks like this: 
    data GhcVer
= Ghc802
| Ghc822
| Ghc844
| Ghc865
| Ghc881
deriving (Eq, Ord, Show, Enum, Bounded)

showGhcVer :: GhcVer -> Text
showGhcVer = \case
Ghc802 -> "8.0.2"
Ghc822 -> "8.2.2"
Ghc844 -> "8.4.4"
Ghc865 -> "8.6.5"
Ghc881 -> "8.8.1"

parseGhcVer :: Text -> Maybe GhcVer
parseGhcVer = inverseMap showGhcVer

  3. bimapBoth :: Bifunctor f => (a -> b) -> f a a -> f b b

    relude Relude.Extra.Bifunctor

    Maps a function over both elements of a bifunctor. 

    >>> bimapBoth length ([True], [False, True])
(1,2)

>>> map (bimapBoth not) [Left True, Right False]
[Left False,Right True]

  4. bimapF :: (Functor f, Bifunctor p) => (a -> c) -> (b -> d) -> f (p a b) -> f (p c d)

    relude Relude.Extra.Bifunctor

    Fmaps functions for nested bifunctor. Short for fmap (bimap f g). 

    >>> bimapF not length $ Just (False, ['a', 'b'])
Just (True,2)

  5. foldMap1 :: (Foldable1 f, Semigroup m) => (a -> m) -> f a -> m

    relude Relude.Extra.Foldable1

    Map each element of the non-empty structure to a semigroup, and combine the results. 

    >>> foldMap1 SG.Sum (1 :| [2, 3, 4])
Sum {getSum = 10}

>>> foldMap1 show (123 :| [456, 789, 0])
"1234567890"

  6. class StaticMap t => DynamicMap t

    relude Relude.Extra.Map

    Modifiable Map.

  7. class StaticMap t

    relude Relude.Extra.Map

    Read-only map or set. Contains polymorphic functions which work for both sets and maps.

  8. fmapToFst :: Functor f => (a -> b) -> f a -> f (b, a)

    relude Relude.Extra.Tuple

    Like fmap, but also keep the original value in the snd position. A dual to fmapToSnd. 

    >>> fmapToFst show [3, 10, 2]
[("3",3),("10",10),("2",2)]

  9. fmapToSnd :: Functor f => (a -> b) -> f a -> f (a, b)

    relude Relude.Extra.Tuple

    Like fmap, but also keep the original value in the fst position. A dual to fmapToFst. 

    >>> fmapToSnd show [3, 10, 2]
[(3,"3"),(10,"10"),(2,"2")]

  10. asumMap :: forall b m f a . (Foldable f, Alternative m) => (a -> m b) -> f a -> m b

    relude Relude.Foldable.Fold

    Alternative version of asum that takes a function to map over. 

    >>> asumMap (\x -> if x > 2 then Just x else Nothing) [1..4]
Just 3

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