Modulerelude-1.2.0.0Haskell2010

Relude.Foldable.Fold

SPDX-License-Identifier : MIT Maintainer : Kowainik xrom.xkov@gmail.com Stability : Stable Portability : Portable

Fixes and additions to Foldable. Specifically:

Space-leak free sum and product
elem and notElem are forbidden for Set and HashSet
Additional combinators for common idioms

12 values

Packagerelude-1.2.0.0
Exports12
LanguageHaskell2010
LicenceMIT
SourceFold.hs

valueflipfoldl' :: Foldable f => (a -> b -> b) -> b -> f a -> b

Similar to foldl' but takes a function with its arguments flipped.

Example1 expression

>>> flipfoldl' (/) 5 [2,3] :: Rational15 % 2

This function can be useful for constructing containers from lists.

valueasumMap :: (Foldable f, Alternative m) => (a -> m b) -> f a -> m b

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

Example1 expression

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

valuefoldMapA

:: (Semigroup b, Monoid b, Applicative m, Foldable f)
=> a -> m b
-> f a
-> m b

Polymorphic version of the Relude.concatMapA function.

Example1 expression

>>> foldMapA @[Int] (Just . replicate 3) [1..3]Just [1,1,1,2,2,2,3,3,3]

valuefoldMapM :: (Monoid b, Monad m, Foldable f) => (a -> m b) -> f a -> m b

Polymorphic version of the Relude.concatMapM function.

Example1 expression

>>> foldMapM @[Int] (Just . replicate 3) [1..3]Just [1,1,1,2,2,2,3,3,3]

valuesum :: (Foldable f, Num a) => f a -> a

Stricter version of sum.

Example1 expression

>>> sum [1..10]55

valueproduct :: (Foldable f, Num a) => f a -> a

Stricter version of product.

Example1 expression

>>> product [1..10]3628800

valueelem :: (Foldable f, DisallowElem f, Eq a) => a -> f a -> Bool

Like elem but doesn't work on Set and HashSet for performance reasons.

Example2 expressions

>>> elem 'x' ("abc" :: String)False>>> elem False (one True :: Set Bool)...... Do not use 'elem' and 'notElem' methods from 'Foldable' on Set      Suggestions:          Instead of              elem :: (Foldable t, Eq a) => a -> t a -> Bool          use              member :: Ord a => a -> Set a -> Bool...          Instead of              notElem :: (Foldable t, Eq a) => a -> t a -> Bool          use              not . member...

valuenotElem :: (Foldable f, DisallowElem f, Eq a) => a -> f a -> Bool

Like notElem but doesn't work on Set and HashSet for performance reasons.

Example2 expressions

>>> notElem 'x' ("abc" :: String)True>>> notElem False (one True :: Set Bool)...... Do not use 'elem' and 'notElem' methods from 'Foldable' on Set      Suggestions:          Instead of              elem :: (Foldable t, Eq a) => a -> t a -> Bool          use              member :: Ord a => a -> Set a -> Bool...          Instead of              notElem :: (Foldable t, Eq a) => a -> t a -> Bool          use              not . member...

Monadic functions

4 declarations

valueallM :: (Foldable f, Monad m) => (a -> m Bool) -> f a -> m Bool

Monadic version of all.

Example3 expressions

>>> allM (readMaybe >=> pure . even) ["6", "10"]Just True>>> allM (readMaybe >=> pure . even) ["5", "aba"]Just False>>> allM (readMaybe >=> pure . even) ["aba", "10"]Nothing

valueanyM :: (Foldable f, Monad m) => (a -> m Bool) -> f a -> m Bool

Monadic version of any.

Example3 expressions

>>> anyM (readMaybe >=> pure . even) ["5", "10"]Just True>>> anyM (readMaybe >=> pure . even) ["10", "aba"]Just True>>> anyM (readMaybe >=> pure . even) ["aba", "10"]Nothing

valueandM :: (Foldable f, Monad m) => f (m Bool) -> m Bool

Monadic version of and.

Example5 expressions

>>> andM [Just True, Just False]Just False>>> andM [Just True]Just True>>> andM [Just True, Just False, Nothing]Just False>>> andM [Just True, Nothing]Nothing>>> andM [putTextLn "1" >> pure True, putTextLn "2" >> pure False, putTextLn "3" >> pure True]12False

valueorM :: (Foldable f, Monad m) => f (m Bool) -> m Bool

Monadic version of or.

Example3 expressions

>>> orM [Just True, Just False]Just True>>> orM [Just True, Nothing]Just True>>> orM [Nothing, Just True]Nothing