Package frege.prelude.Maybe

Compiled: Wed Dec 05 00:00:21 PST 2012 from source file: ./frege/prelude/Maybe.fr

Package Documentation

Provides functions and instances for the Maybe type.

Compatible with the Haskell 2010 /Data.Maybe/ module.

Table of Content

Imports

Instances

instance Empty Maybe

Member Functions

empty :: Maybe α
null :: Maybe α -> Bool
instance Eq Eq a => Maybe a

Member Functions

!= :: Eq α => Maybe α -> Maybe α -> Bool

inherited from Eq.!=

/= :: Eq α => Maybe α -> Maybe α -> Bool

inherited from Eq./=

== :: Eq α => Maybe α -> Maybe α -> Bool

Function generated for derived istance.

hashCode :: Eq α => Maybe α -> Int

Function generated for derived istance.

instance Functor Maybe

Member Functions

fmap :: (α->β) -> Maybe α -> Maybe β
instance MonadFail Maybe

Member Functions

fail :: String -> Maybe α
instance MonadPlus Maybe

Member Functions

mplus :: Maybe α -> Maybe α -> Maybe α
mzero :: Maybe α
instance Monad Maybe

Member Functions

*> :: Maybe α -> Maybe β -> Maybe β

inherited from Applicative.*>

<* :: Maybe α -> Maybe β -> Maybe α

inherited from Applicative.<*

<*> :: Maybe (α->β) -> Maybe α -> Maybe β

inherited from Monad.<*>

>> :: Maybe α -> Maybe β -> Maybe β
>>= :: Maybe α -> (α->Maybe β) -> Maybe β
join :: Maybe (Maybe α) -> Maybe α

inherited from Monad.join

return :: α -> Maybe α
instance Ord Ord a => Maybe a

Member Functions

< :: Ord α => Maybe α -> Maybe α -> Bool

inherited from Ord.<

<= :: Ord α => Maybe α -> Maybe α -> Bool

inherited from Ord.<=

<=> :: Ord α => Maybe α -> Maybe α -> Ordering

Function generated for derived istance.

> :: Ord α => Maybe α -> Maybe α -> Bool

inherited from Ord.>

>= :: Ord α => Maybe α -> Maybe α -> Bool

inherited from Ord.>=

compare :: Ord α => Maybe α -> Maybe α -> Ordering

inherited from Ord.compare

max :: Ord α => Maybe α -> Maybe α -> Maybe α

inherited from Ord.max

min :: Ord α => Maybe α -> Maybe α -> Maybe α

inherited from Ord.min

Functions and Values

catMaybes :: ListSource α => α (Maybe β) -> [β]

The catMaybes function takes a list of Maybes and returns a list of all the Maybe.Just values.

fromMaybe :: α -> Maybe α -> α

fromMaybe d (Just a) returns a and fromMaybe d Nothing returns d

isJust :: Maybe α -> Bool

true if and only if the argument is a Maybe.Just value

isNothing :: Maybe α -> Bool

true if and only if the argument is Maybe.Nothing

This function is preferrable over v == Nothing because no Eq constraint is needed.

listToMaybe :: ListSource α => α β -> Maybe β

give the first element of a list or Maybe.Nothing

mapMaybe :: (α->Maybe β) -> [α] -> [β]

The mapMaybe function is a version of map which can throw out elements. In particular, the functional argument returns something of type Maybe /b/. If this is Maybe.Nothing, no element is added on to the result list. If it just Maybe.Just /b/, then /b/ is included in the result list.

maybeToList :: Maybe a -> [a]

convert a Maybe to a single element list or an empty list

unJust :: Maybe α -> α

unJust Nothing is undefined whereas unJust (Just a) is a

Functions and Values by Type

Maybe (Maybe α) -> Maybe α

Monad_Maybe.join

Maybe a -> [a]

maybeToList

Maybe α -> Maybe α -> Maybe α

MonadPlus_Maybe.mplus

Maybe α -> Bool

isJust, isNothing, Empty_Maybe.null

Maybe α -> α

unJust

String -> Maybe α

MonadFail_Maybe.fail

α -> Maybe α -> α

fromMaybe

α -> Maybe α

Monad_Maybe.return

Eq α => Maybe α -> Maybe α -> Bool

Eq_Maybe./=, Eq_Maybe.!=, Eq_Maybe.==

Eq α => Maybe α -> Int

Eq_Maybe.hashCode

Ord α => Maybe α -> Maybe α -> Maybe α

Ord_Maybe.max, Ord_Maybe.min

Ord α => Maybe α -> Maybe α -> Bool

Ord_Maybe.>, Ord_Maybe.<=, Ord_Maybe.<, Ord_Maybe.>=

Ord α => Maybe α -> Maybe α -> Ordering

Ord_Maybe.<=>, Ord_Maybe.compare

Maybe α

Empty_Maybe.empty, MonadPlus_Maybe.mzero

(α->Maybe β) -> [α] -> [β]

mapMaybe

(α->β) -> Maybe α -> Maybe β

Functor_Maybe.fmap

Maybe (α->β) -> Maybe α -> Maybe β

Monad_Maybe.<*>

Maybe α -> (α->Maybe β) -> Maybe β

Monad_Maybe.>>=

Maybe α -> Maybe β -> Maybe α

Monad_Maybe.<*

Maybe α -> Maybe β -> Maybe β

Monad_Maybe.*>, Monad_Maybe.>>

ListSource α => α (Maybe β) -> [β]

catMaybes

ListSource α => α β -> Maybe β

listToMaybe

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