Module Maybe

isJust :: Maybe a -> Bool   

Return True iff the argument is of the form Just _.

Further infos:

• solution complete, i.e., able to compute all solutions

isNothing :: Maybe a -> Bool   

Return True iff the argument is of the form Nothing.

Further infos:

• solution complete, i.e., able to compute all solutions

fromJust :: Maybe a -> a   

Extract the argument from the Just constructor and throw an error if the argument is Nothing.

fromMaybe :: a -> Maybe a -> a   

Extract the argument from the Just constructor or return the provided default value if the argument is Nothing.

Further infos:

• solution complete, i.e., able to compute all solutions

listToMaybe :: [a] -> Maybe a   

Return Nothing on an empty list or Just x where x is the first list element.

Further infos:

• solution complete, i.e., able to compute all solutions

maybeToList :: Maybe a -> [a]   

Return an empty list for Nothing or a singleton list for Just x.

Further infos:

• solution complete, i.e., able to compute all solutions

catMaybes :: [Maybe a] -> [a]   

Return the list of all Just values.

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

Apply a function which may throw out elements using the Nothing constructor to a list of elements.

(>>-) :: Maybe a -> (a -> Maybe b) -> Maybe b   

Monadic bind for Maybe. Maybe can be interpreted as a monad where Nothing is interpreted as the error case by this monadic binding.

Example call:

(maybeValue >>- f)

Parameters:

• maybeValue : Nothing or Just x
• f : function to be applied to x

Returns:

Nothing if maybeValue is Nothing, otherwise f is applied to x

Further infos:

• defined as left-associative infix operator with precedence 1

sequenceMaybe :: [Maybe a] -> Maybe [a]   

Monadic sequence for Maybe.

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

Monadic map for Maybe.

mplus :: Maybe a -> Maybe a -> Maybe a   

Combine two Maybes, returning the first Just value, if any.

Further infos:

• solution complete, i.e., able to compute all solutions