takeWhile package:utility-ht

Alternative version of reverse . takeWhile p . reverse.

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

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

\x xs pad -> defined $ Rev.takeWhile ((x::Char)/=) $ Match.replicate (pad::[()]) undefined ++ x:xs

This is the cousin of takeWhile analogously to catMaybes being the cousin of filter.

>>> takeWhileJust [Just 'a', Just 'b', Nothing, Just 'c']
"ab"

Example: Keep the heads of sublists until an empty list occurs.

>>> takeWhileJust $ map (fmap fst . viewL) ["abc","def","","xyz"]
"ad"

For consistency with takeWhile, partitionMaybe and dropWhileNothing it should have been:

takeWhileJust_ :: (a -> Maybe b) -> a -> [b]

However, both variants are interchangeable:

takeWhileJust_ f == takeWhileJust . map f
takeWhileJust == takeWhileJust_ id

Take while first predicate holds, then continue taking while second predicate holds, and so on.

Deprecated: Use takeWhile from Data.List.Reverse.StrictElement or Data.List.Reverse.StrictSpine instead