Moduleutility-ht-0.0.17.2Haskell98

Data.List.Reverse.StrictElement

The functions in this module process the list formally from the end. Actually they traverse the list from the start and check every element. This way they are strict in the elements and lazy in the list spline. Thus you can apply them to infinite lists. Use these functions if the list is long or the test is cheap.

3 values

Packageutility-ht-0.0.17.2
Exports3
LanguageHaskell98
LicenceBSD-3-Clause
SourceStrictElement.hs

Example8 expressions

>>> import Test.Utility (forAllPredicates, defined)>>> import qualified Data.List.Reverse.StrictElement as Rev>>> import qualified Data.List.Match as Match>>> import qualified Data.List as List>>> import Data.Tuple.HT (mapPair, swap)>>> >>> _suppressUnusedImportWarning :: (a -> Bool) -> [a] -> [a]>>> _suppressUnusedImportWarning = Data.List.Reverse.StrictElement.dropWhile

valuedropWhile :: (a -> Bool) -> [a] -> [a]

Remove the longest suffix of elements satisfying p. In contrast to reverse . dropWhile p . reverse this works for infinite lists, too.

Property

prop> forAllPredicates $ \p xs -> Rev.dropWhile p xs == reverse (List.dropWhile p (reverse xs))

Property

prop> \x xs pad -> defined $ Match.take (pad::[()]) $ Rev.dropWhile ((x::Char)/=) $ cycle $ x:xs

valuetakeWhile :: (a -> Bool) -> [a] -> [a]

Alternative version of reverse . takeWhile p . reverse.

Property

prop> forAllPredicates $ \p xs -> Rev.takeWhile p xs == reverse (List.takeWhile p (reverse xs))

valuespan :: (a -> Bool) -> [a] -> ([a], [a])

Property

prop> forAllPredicates $ \p xs -> Rev.span p xs == swap (mapPair (reverse, reverse) (List.span p (reverse xs)))

Property

prop> forAllPredicates $ \p xs -> Rev.span p xs == (Rev.dropWhile p xs, Rev.takeWhile p xs)

Property

prop> \x xs pad -> defined $ Match.take (pad::[()]) $ fst $ Rev.span ((x::Char)/=) $ cycle $ x:xs