Data.Array.Accelerate.Data.Maybe

Since: 1.2.0.0

Documentation

data Maybe a

The Maybe type encapsulates an optional value. A value of type Maybe a either contains a value of type a (represented as Just a), or it is empty (represented as Nothing). Using Maybe is a good way to deal with errors or exceptional cases without resorting to drastic measures such as error.

The Maybe type is also a monad. It is a simple kind of error monad, where all errors are represented by Nothing. A richer error monad can be built using the Either type.

Constructors

Nothing

Just a

Instances

Monad Maybe

Since: 2.1

Methods

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

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

return :: a -> Maybe a

fail :: String -> Maybe a

Functor Maybe

Since: 2.1

Methods

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

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

MonadFix Maybe

Since: 2.1

Methods

mfix :: (a -> Maybe a) -> Maybe a

MonadFail Maybe

Since: 4.9.0.0

Methods

fail :: String -> Maybe a

Applicative Maybe

Since: 2.1

Methods

pure :: a -> Maybe a

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

liftA2 :: (a -> b -> c) -> Maybe a -> Maybe b -> Maybe c

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

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

Foldable Maybe

Since: 2.1

Methods

fold :: Monoid m => Maybe m -> m

foldMap :: Monoid m => (a -> m) -> Maybe a -> m

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

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

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

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

foldr1 :: (a -> a -> a) -> Maybe a -> a

foldl1 :: (a -> a -> a) -> Maybe a -> a

toList :: Maybe a -> [a]

null :: Maybe a -> Bool

length :: Maybe a -> Int

elem :: Eq a => a -> Maybe a -> Bool

maximum :: Ord a => Maybe a -> a

minimum :: Ord a => Maybe a -> a

sum :: Num a => Maybe a -> a

product :: Num a => Maybe a -> a

Traversable Maybe

Since: 2.1

Methods

traverse :: Applicative f => (a -> f b) -> Maybe a -> f (Maybe b)

sequenceA :: Applicative f => Maybe (f a) -> f (Maybe a)

mapM :: Monad m => (a -> m b) -> Maybe a -> m (Maybe b)

sequence :: Monad m => Maybe (m a) -> m (Maybe a)

Eq1 Maybe

Since: 4.9.0.0

Methods

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

Ord1 Maybe

Since: 4.9.0.0

Methods

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

Read1 Maybe

Since: 4.9.0.0

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Maybe a)

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Maybe a]

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Maybe a)

liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Maybe a]

Show1 Maybe

Since: 4.9.0.0

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Maybe a -> ShowS

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Maybe a] -> ShowS

Alternative Maybe

Since: 2.1

Methods

empty :: Maybe a

(<|>) :: Maybe a -> Maybe a -> Maybe a

some :: Maybe a -> Maybe [a]

many :: Maybe a -> Maybe [a]

MonadPlus Maybe

Since: 2.1

Methods

mzero :: Maybe a

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

MonadFailure Maybe

Associated Types

type Failure Maybe :: *

Methods

mFail :: Failure Maybe -> Maybe ()

MonadThrow Maybe

Methods

throwM :: Exception e => e -> Maybe a

NFData1 Maybe

Since: 1.4.3.0

Methods

liftRnf :: (a -> ()) -> Maybe a -> ()

Hashable1 Maybe

Methods

liftHashWithSalt :: (Int -> a -> Int) -> Int -> Maybe a -> Int

Functor Maybe

Methods

fmap :: (Elt a, Elt b, Elt (Maybe a), Elt (Maybe b)) => (Exp a -> Exp b) -> Exp (Maybe a) -> Exp (Maybe b)

(<$) :: (Elt a, Elt b, Elt (Maybe a), Elt (Maybe b)) => Exp a -> Exp (Maybe b) -> Exp (Maybe a)

FunctorWithIndex () Maybe

Methods

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

imapped :: (Indexable () p, Settable f) => p a (f b) -> Maybe a -> f (Maybe b)

FoldableWithIndex () Maybe

Methods

ifoldMap :: Monoid m => (() -> a -> m) -> Maybe a -> m

ifolded :: (Indexable () p, Contravariant f, Applicative f) => p a (f a) -> Maybe a -> f (Maybe a)

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

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

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

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

TraversableWithIndex () Maybe

Methods

itraverse :: Applicative f => (() -> a -> f b) -> Maybe a -> f (Maybe b)

itraversed :: (Indexable () p, Applicative f) => p a (f b) -> Maybe a -> f (Maybe b)

MonadBaseControl Maybe Maybe

Associated Types

type StM Maybe a :: *

Methods

liftBaseWith :: (RunInBase Maybe Maybe -> Maybe a) -> Maybe a

restoreM :: StM Maybe a -> Maybe a

() :=> (Functor Maybe)

Methods

ins :: () :- Functor Maybe

() :=> (Applicative Maybe)

Methods

ins :: () :- Applicative Maybe

() :=> (Alternative Maybe)

Methods

ins :: () :- Alternative Maybe

() :=> (MonadPlus Maybe)

Methods

ins :: () :- MonadPlus Maybe

(Lift Exp a, Elt (Plain a)) => Lift Exp (Maybe a)

Associated Types

type Plain (Maybe a) :: *

Methods

lift :: Maybe a -> Exp (Plain (Maybe a))

Eq a => Eq (Maybe a)

Methods

(==) :: Maybe a -> Maybe a -> Bool

(/=) :: Maybe a -> Maybe a -> Bool

Ord a => Ord (Maybe a)

Methods

compare :: Maybe a -> Maybe a -> Ordering

(<) :: Maybe a -> Maybe a -> Bool

(<=) :: Maybe a -> Maybe a -> Bool

(>) :: Maybe a -> Maybe a -> Bool

(>=) :: Maybe a -> Maybe a -> Bool

max :: Maybe a -> Maybe a -> Maybe a

min :: Maybe a -> Maybe a -> Maybe a

Read a => Read (Maybe a)

Since: 2.1

Methods

readsPrec :: Int -> ReadS (Maybe a)

readList :: ReadS [Maybe a]

readPrec :: ReadPrec (Maybe a)

readListPrec :: ReadPrec [Maybe a]

Show a => Show (Maybe a)

Methods

showsPrec :: Int -> Maybe a -> ShowS

show :: Maybe a -> String

showList :: [Maybe a] -> ShowS

Generic (Maybe a)

Associated Types

type Rep (Maybe a) :: * -> *

Methods

from :: Maybe a -> Rep (Maybe a) x

to :: Rep (Maybe a) x -> Maybe a

Semigroup a => Semigroup (Maybe a)

Since: 4.9.0.0

Methods

(<>) :: Maybe a -> Maybe a -> Maybe a

sconcat :: NonEmpty (Maybe a) -> Maybe a

stimes :: Integral b => b -> Maybe a -> Maybe a

(Semigroup (Exp a), Elt a) => Semigroup (Exp (Maybe a))

Methods

(<>) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp (Maybe a)

sconcat :: NonEmpty (Exp (Maybe a)) -> Exp (Maybe a)

stimes :: Integral b => b -> Exp (Maybe a) -> Exp (Maybe a)

Semigroup a => Monoid (Maybe a)

Lift a semigroup into Maybe forming a Monoid according to http://en.wikipedia.org/wiki/Monoid: "Any semigroup S may be turned into a monoid simply by adjoining an element e not in S and defining e*e = e and e*s = s = s*e for all s ∈ S."

Since 4.11.0: constraint on inner a value generalised from Monoid to Semigroup.

Since: 2.1

Methods

mempty :: Maybe a

mappend :: Maybe a -> Maybe a -> Maybe a

mconcat :: [Maybe a] -> Maybe a

(Monoid (Exp a), Elt a) => Monoid (Exp (Maybe a))

Methods

mempty :: Exp (Maybe a)

mappend :: Exp (Maybe a) -> Exp (Maybe a) -> Exp (Maybe a)

mconcat :: [Exp (Maybe a)] -> Exp (Maybe a)

Lift a => Lift (Maybe a)

Methods

lift :: Maybe a -> Q Exp

Pretty a => Pretty (Maybe a)

Methods

pretty :: Maybe a -> Doc

prettyList :: [Maybe a] -> Doc

SingKind a => SingKind (Maybe a)

Since: 4.9.0.0

Associated Types

type DemoteRep (Maybe a) :: *

Methods

fromSing :: Sing a0 -> DemoteRep (Maybe a)

NFData a => NFData (Maybe a)

Methods

rnf :: Maybe a -> ()

Hashable a => Hashable (Maybe a)

Methods

hashWithSalt :: Int -> Maybe a -> Int

hash :: Maybe a -> Int

Ixed (Maybe a)

Methods

ix :: Index (Maybe a) -> Traversal' (Maybe a) (IxValue (Maybe a))

At (Maybe a)

Methods

at :: Index (Maybe a) -> Lens' (Maybe a) (Maybe (IxValue (Maybe a)))

AsEmpty (Maybe a)

Methods

_Empty :: Prism' (Maybe a) ()

Pretty a => Pretty (Maybe a)

Methods

pretty :: Maybe a -> Doc b

prettyList :: [Maybe a] -> Doc b

Elt a => Elt (Maybe a)

Methods

eltType :: Maybe a -> TupleType (EltRepr (Maybe a))

fromElt :: Maybe a -> EltRepr (Maybe a)

toElt :: EltRepr (Maybe a) -> Maybe a

Eq a => Eq (Maybe a)

Methods

(==) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

(/=) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

Ord a => Ord (Maybe a)

Methods

(<) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

(>) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

(<=) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

(>=) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

min :: Exp (Maybe a) -> Exp (Maybe a) -> Exp (Maybe a)

max :: Exp (Maybe a) -> Exp (Maybe a) -> Exp (Maybe a)

compare :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Ordering

Generic1 Maybe

Associated Types

type Rep1 Maybe :: k -> *

Methods

from1 :: Maybe a -> Rep1 Maybe a

to1 :: Rep1 Maybe a -> Maybe a

SingI (Nothing :: Maybe a)

Since: 4.9.0.0

Methods

sing :: Sing Nothing

(Eq a) :=> (Eq (Maybe a))

Methods

ins :: Eq a :- Eq (Maybe a)

(Ord a) :=> (Ord (Maybe a))

Methods

ins :: Ord a :- Ord (Maybe a)

(Read a) :=> (Read (Maybe a))

Methods

ins :: Read a :- Read (Maybe a)

(Show a) :=> (Show (Maybe a))

Methods

ins :: Show a :- Show (Maybe a)

(Semigroup a) :=> (Semigroup (Maybe a))

Methods

ins :: Semigroup a :- Semigroup (Maybe a)

(Monoid a) :=> (Monoid (Maybe a))

Methods

ins :: Monoid a :- Monoid (Maybe a)

Each (Maybe a) (Maybe b) a b

each :: Traversal (Maybe a) (Maybe b) a b

Methods

each :: Traversal (Maybe a) (Maybe b) a b

SingI a2 => SingI (Just a2 :: Maybe a1)

Since: 4.9.0.0

Methods

sing :: Sing (Just a2)

type Failure Maybe

type Failure Maybe = ()

type StM Maybe a

type StM Maybe a = a

type Rep (Maybe a)

type Rep (Maybe a) = D1 (MetaData "Maybe" "GHC.Base" "base" False) (C1 (MetaCons "Nothing" PrefixI False) (U1 :: * -> *) :+: C1 (MetaCons "Just" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 a)))

data Sing (b :: Maybe a)

data Sing (b :: Maybe a) where

• SNothing :: Sing (Nothing :: Maybe a)
• SJust :: Sing (Just a1)

type DemoteRep (Maybe a)

type DemoteRep (Maybe a) = Maybe (DemoteRep a)

type Index (Maybe a)

type Index (Maybe a) = ()

type IxValue (Maybe a)

type IxValue (Maybe a) = a

type Plain (Maybe a)

type Plain (Maybe a) = Maybe (Plain a)

type Rep1 Maybe

type Rep1 Maybe = D1 (MetaData "Maybe" "GHC.Base" "base" False) (C1 (MetaCons "Nothing" PrefixI False) (U1 :: * -> *) :+: C1 (MetaCons "Just" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) Par1))

just :: Elt a => Exp a -> Exp (Maybe a)

Lift a value into a Just constructor

nothing :: forall a. Elt a => Exp (Maybe a)

The Nothing constructor

maybe :: (Elt a, Elt b) => Exp b -> (Exp a -> Exp b) -> Exp (Maybe a) -> Exp b

The maybe function takes a default value, a function, and a Maybe value. If the Maybe value is nothing, the default value is returned; otherwise, it applies the function to the value inside the Just and returns the result

isJust :: Elt a => Exp (Maybe a) -> Exp Bool

Returns True if the argument is of the form Just _

isNothing :: Elt a => Exp (Maybe a) -> Exp Bool

Returns True if the argument is Nothing

fromMaybe :: Elt a => Exp a -> Exp (Maybe a) -> Exp a

The fromMaybe function takes a default value and a Maybe value. If the Maybe is Nothing, the default value is returned; otherwise, it returns the value contained in the Maybe.

fromJust :: Elt a => Exp (Maybe a) -> Exp a

The fromJust function extracts the element out of the Just constructor. If the argument was actually Nothing, you will get an undefined value instead.

justs :: (Shape sh, Slice sh, Elt a) => Acc (Array (sh :. Int) (Maybe a)) -> Acc (Vector a, Array sh Int)

Extract from an array all of the Just values, together with a segment descriptor indicating how many elements along each dimension were returned.

Orphan instances

Functor Maybe

Methods

fmap :: (Elt a, Elt b, Elt (Maybe a), Elt (Maybe b)) => (Exp a -> Exp b) -> Exp (Maybe a) -> Exp (Maybe b)

(<$) :: (Elt a, Elt b, Elt (Maybe a), Elt (Maybe b)) => Exp a -> Exp (Maybe b) -> Exp (Maybe a)

(Lift Exp a, Elt (Plain a)) => Lift Exp (Maybe a)

Associated Types

type Plain (Maybe a) :: *

Methods

lift :: Maybe a -> Exp (Plain (Maybe a))

(Semigroup (Exp a), Elt a) => Semigroup (Exp (Maybe a))

Methods

(<>) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp (Maybe a)

sconcat :: NonEmpty (Exp (Maybe a)) -> Exp (Maybe a)

stimes :: Integral b => b -> Exp (Maybe a) -> Exp (Maybe a)

(Monoid (Exp a), Elt a) => Monoid (Exp (Maybe a))

Methods

mempty :: Exp (Maybe a)

mappend :: Exp (Maybe a) -> Exp (Maybe a) -> Exp (Maybe a)

mconcat :: [Exp (Maybe a)] -> Exp (Maybe a)

Elt a => Elt (Maybe a)

Methods

eltType :: Maybe a -> TupleType (EltRepr (Maybe a))

fromElt :: Maybe a -> EltRepr (Maybe a)

toElt :: EltRepr (Maybe a) -> Maybe a

Eq a => Eq (Maybe a)

Methods

(==) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

(/=) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

Ord a => Ord (Maybe a)

Methods

(<) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

(>) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

(<=) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

(>=) :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Bool

min :: Exp (Maybe a) -> Exp (Maybe a) -> Exp (Maybe a)

max :: Exp (Maybe a) -> Exp (Maybe a) -> Exp (Maybe a)

compare :: Exp (Maybe a) -> Exp (Maybe a) -> Exp Ordering