| Safe Haskell | Safe |
|---|---|
| Language | Haskell2010 |
Universum.List.Safe
Description
This module contains safe functions to work with list type (mostly with NonEmpty).
Synopsis
- uncons :: [a] -> Maybe (a, [a])
- whenNotNull :: Applicative f => [a] -> (NonEmpty a -> f ()) -> f ()
- whenNotNullM :: Monad m => m [a] -> (NonEmpty a -> m ()) -> m ()
Documentation
uncons :: [a] -> Maybe (a, [a]) Source #
Destructuring list into its head and tail if possible. This function is total.
>>>uncons []Nothing>>>uncons [1..5]Just (1,[2,3,4,5])>>>uncons (5 : [1..5]) >>= \(f, l) -> pure $ f == length lJust True
whenNotNull :: Applicative f => [a] -> (NonEmpty a -> f ()) -> f () Source #
Performs given action over NonEmpty list if given list is non empty.
>>>whenNotNull [] $ \(b :| _) -> print (not b)>>>whenNotNull [False,True] $ \(b :| _) -> print (not b)True
whenNotNullM :: Monad m => m [a] -> (NonEmpty a -> m ()) -> m () Source #
Monadic version of whenNotNull.