Safe Haskell | Safe-Inferred |
---|---|

Language | Haskell98 |

A module wrapping `Prelude`

/`Data.List`

functions that can throw exceptions, such as `head`

and `!!`

.
Each unsafe function has up to four variants, e.g. with `tail`

:

, raises an error on`tail`

:: [a] -> [a]`tail []`

.

, turns errors into`tailMay`

:: [a] ->*Maybe*[a]`Nothing`

.

, takes a default to return on errors.`tailDef`

::*[a]*-> [a] -> [a]

, takes an extra argument which supplements the error message.`tailNote`

::*String*-> [a] -> [a]

, returns some sensible default if possible,`tailSafe`

:: [a] -> [a]`[]`

in the case of`tail`

.

This module also introduces some new functions, documented at the top of the module.

- abort :: String -> a
- at :: [a] -> Int -> a
- lookupJust :: Eq a => a -> [(a, b)] -> b
- findJust :: (a -> Bool) -> [a] -> a
- elemIndexJust :: Eq a => a -> [a] -> Int
- findIndexJust :: (a -> Bool) -> [a] -> Int
- tailMay :: [a] -> Maybe [a]
- tailDef :: [a] -> [a] -> [a]
- tailNote :: String -> [a] -> [a]
- tailSafe :: [a] -> [a]
- initMay :: [a] -> Maybe [a]
- initDef :: [a] -> [a] -> [a]
- initNote :: String -> [a] -> [a]
- initSafe :: [a] -> [a]
- headMay :: [a] -> Maybe a
- headDef :: a -> [a] -> a
- headNote :: String -> [a] -> a
- lastMay :: [a] -> Maybe a
- lastDef :: a -> [a] -> a
- lastNote :: String -> [a] -> a
- minimumMay :: Ord a => [a] -> Maybe a
- minimumDef :: Ord a => a -> [a] -> a
- minimumNote :: Ord a => String -> [a] -> a
- maximumMay :: Ord a => [a] -> Maybe a
- maximumDef :: Ord a => a -> [a] -> a
- maximumNote :: Ord a => String -> [a] -> a
- minimumByMay :: (a -> a -> Ordering) -> [a] -> Maybe a
- minimumByDef :: a -> (a -> a -> Ordering) -> [a] -> a
- minimumByNote :: String -> (a -> a -> Ordering) -> [a] -> a
- maximumByMay :: (a -> a -> Ordering) -> [a] -> Maybe a
- maximumByDef :: a -> (a -> a -> Ordering) -> [a] -> a
- maximumByNote :: String -> (a -> a -> Ordering) -> [a] -> a
- foldr1May :: (a -> a -> a) -> [a] -> Maybe a
- foldr1Def :: a -> (a -> a -> a) -> [a] -> a
- foldr1Note :: String -> (a -> a -> a) -> [a] -> a
- foldl1May :: (a -> a -> a) -> [a] -> Maybe a
- foldl1Def :: a -> (a -> a -> a) -> [a] -> a
- foldl1Note :: String -> (a -> a -> a) -> [a] -> a
- foldl1May' :: (a -> a -> a) -> [a] -> Maybe a
- foldl1Def' :: a -> (a -> a -> a) -> [a] -> a
- foldl1Note' :: String -> (a -> a -> a) -> [a] -> a
- scanl1May :: (a -> a -> a) -> [a] -> Maybe [a]
- scanl1Def :: [a] -> (a -> a -> a) -> [a] -> [a]
- scanl1Note :: String -> (a -> a -> a) -> [a] -> [a]
- scanr1May :: (a -> a -> a) -> [a] -> Maybe [a]
- scanr1Def :: [a] -> (a -> a -> a) -> [a] -> [a]
- scanr1Note :: String -> (a -> a -> a) -> [a] -> [a]
- fromJustDef :: a -> Maybe a -> a
- fromJustNote :: String -> Maybe a -> a
- assertNote :: String -> Bool -> a -> a
- atMay :: [a] -> Int -> Maybe a
- atDef :: a -> [a] -> Int -> a
- atNote :: String -> [a] -> Int -> a
- readMay :: Read a => String -> Maybe a
- readDef :: Read a => a -> String -> a
- readNote :: Read a => String -> String -> a
- lookupJustDef :: Eq a => b -> a -> [(a, b)] -> b
- lookupJustNote :: Eq a => String -> a -> [(a, b)] -> b
- findJustDef :: a -> (a -> Bool) -> [a] -> a
- findJustNote :: String -> (a -> Bool) -> [a] -> a
- elemIndexJustDef :: Eq a => Int -> a -> [a] -> Int
- elemIndexJustNote :: Eq a => String -> a -> [a] -> Int
- findIndexJustDef :: Int -> (a -> Bool) -> [a] -> Int
- findIndexJustNote :: String -> (a -> Bool) -> [a] -> Int
- toEnumMay :: (Enum a, Bounded a) => Int -> Maybe a
- toEnumDef :: (Enum a, Bounded a) => a -> Int -> a
- toEnumNote :: (Enum a, Bounded a) => String -> Int -> a
- toEnumSafe :: (Enum a, Bounded a) => Int -> a

# New functions

lookupJust :: Eq a => a -> [(a, b)] -> b Source

lookupJust key = fromJust . lookup key

elemIndexJust :: Eq a => a -> [a] -> Int Source

elemIndexJust op = fromJust . elemIndex op

findIndexJust :: (a -> Bool) -> [a] -> Int Source

findIndexJust op = fromJust . findIndex op

# Safe wrappers

tailNote :: String -> [a] -> [a] Source

tailNote "help me" [] = error "Safe.tailNote [], help me" tailNote "help me" [1,3,4] = [3,4]

minimumMay :: Ord a => [a] -> Maybe a Source

minimumDef :: Ord a => a -> [a] -> a Source

minimumNote :: Ord a => String -> [a] -> a Source

maximumMay :: Ord a => [a] -> Maybe a Source

maximumDef :: Ord a => a -> [a] -> a Source

maximumNote :: Ord a => String -> [a] -> a Source

minimumByMay :: (a -> a -> Ordering) -> [a] -> Maybe a Source

minimumByDef :: a -> (a -> a -> Ordering) -> [a] -> a Source

minimumByNote :: String -> (a -> a -> Ordering) -> [a] -> a Source

maximumByMay :: (a -> a -> Ordering) -> [a] -> Maybe a Source

maximumByDef :: a -> (a -> a -> Ordering) -> [a] -> a Source

maximumByNote :: String -> (a -> a -> Ordering) -> [a] -> a Source

foldr1Note :: String -> (a -> a -> a) -> [a] -> a Source

foldl1Note :: String -> (a -> a -> a) -> [a] -> a Source

foldl1May' :: (a -> a -> a) -> [a] -> Maybe a Source

foldl1Def' :: a -> (a -> a -> a) -> [a] -> a Source

foldl1Note' :: String -> (a -> a -> a) -> [a] -> a Source

scanl1Note :: String -> (a -> a -> a) -> [a] -> [a] Source

scanr1Note :: String -> (a -> a -> a) -> [a] -> [a] Source

fromJustDef :: a -> Maybe a -> a Source

fromJustNote :: String -> Maybe a -> a Source

assertNote :: String -> Bool -> a -> a Source

lookupJustDef :: Eq a => b -> a -> [(a, b)] -> b Source

lookupJustNote :: Eq a => String -> a -> [(a, b)] -> b Source

findJustDef :: a -> (a -> Bool) -> [a] -> a Source

findJustNote :: String -> (a -> Bool) -> [a] -> a Source

elemIndexJustDef :: Eq a => Int -> a -> [a] -> Int Source

elemIndexJustNote :: Eq a => String -> a -> [a] -> Int Source

findIndexJustDef :: Int -> (a -> Bool) -> [a] -> Int Source

findIndexJustNote :: String -> (a -> Bool) -> [a] -> Int Source

toEnumSafe :: (Enum a, Bounded a) => Int -> a Source