Safe Haskell | None |
---|---|
Language | Haskell2010 |
PlutusTx.Either
Documentation
The
Either
type represents values with two possibilities: a value of
type
is either
Either
a b
or
Left
a
.
Right
b
The
Either
type is sometimes used to represent a value which is
either correct or an error; by convention, the
Left
constructor is
used to hold an error value and the
Right
constructor is used to
hold a correct value (mnemonic: "right" also means "correct").
Examples
The type
is the type of values which can be either
a
Either
String
Int
String
or an
Int
. The
Left
constructor can be used only on
String
s, and the
Right
constructor can be used only on
Int
s:
>>>
let s = Left "foo" :: Either String Int
>>>
s
Left "foo">>>
let n = Right 3 :: Either String Int
>>>
n
Right 3>>>
:type s
s :: Either String Int>>>
:type n
n :: Either String Int
The
fmap
from our
Functor
instance will ignore
Left
values, but
will apply the supplied function to values contained in a
Right
:
>>>
let s = Left "foo" :: Either String Int
>>>
let n = Right 3 :: Either String Int
>>>
fmap (*2) s
Left "foo">>>
fmap (*2) n
Right 6
The
Monad
instance for
Either
allows us to chain together multiple
actions which may fail, and fail overall if any of the individual
steps failed. First we'll write a function that can either parse an
Int
from a
Char
, or fail.
>>>
import Data.Char ( digitToInt, isDigit )
>>>
:{
let parseEither :: Char -> Either String Int parseEither c | isDigit c = Right (digitToInt c) | otherwise = Left "parse error">>>
:}
The following should work, since both
'1'
and
'2'
can be
parsed as
Int
s.
>>>
:{
let parseMultiple :: Either String Int parseMultiple = do x <- parseEither '1' y <- parseEither '2' return (x + y)>>>
:}
>>>
parseMultiple
Right 3
But the following should fail overall, since the first operation where
we attempt to parse
'm'
as an
Int
will fail:
>>>
:{
let parseMultiple :: Either String Int parseMultiple = do x <- parseEither 'm' y <- parseEither '2' return (x + y)>>>
:}
>>>
parseMultiple
Left "parse error"
Instances
ToJSON2 Either | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a -> Value ) -> ([a] -> Value ) -> (b -> Value ) -> ([b] -> Value ) -> Either a b -> Value Source # liftToJSONList2 :: (a -> Value ) -> ([a] -> Value ) -> (b -> Value ) -> ([b] -> Value ) -> [ Either a b] -> Value Source # liftToEncoding2 :: (a -> Encoding ) -> ([a] -> Encoding ) -> (b -> Encoding ) -> ([b] -> Encoding ) -> Either a b -> Encoding Source # liftToEncodingList2 :: (a -> Encoding ) -> ([a] -> Encoding ) -> (b -> Encoding ) -> ([b] -> Encoding ) -> [ Either a b] -> Encoding Source # |
|
FromJSON2 Either | |
Defined in Data.Aeson.Types.FromJSON Methods liftParseJSON2 :: ( Value -> Parser a) -> ( Value -> Parser [a]) -> ( Value -> Parser b) -> ( Value -> Parser [b]) -> Value -> Parser ( Either a b) Source # liftParseJSONList2 :: ( Value -> Parser a) -> ( Value -> Parser [a]) -> ( Value -> Parser b) -> ( Value -> Parser [b]) -> Value -> Parser [ Either a b] Source # |
|
Bifunctor Either |
Since: base-4.8.0.0 |
Bifoldable Either |
Since: base-4.10.0.0 |
Defined in Data.Bifoldable |
|
Eq2 Either |
Since: base-4.9.0.0 |
Ord2 Either |
Since: base-4.9.0.0 |
Defined in Data.Functor.Classes |
|
Read2 Either |
Since: base-4.9.0.0 |
Defined in Data.Functor.Classes Methods liftReadsPrec2 :: ( Int -> ReadS a) -> ReadS [a] -> ( Int -> ReadS b) -> ReadS [b] -> Int -> ReadS ( Either a b) Source # liftReadList2 :: ( Int -> ReadS a) -> ReadS [a] -> ( Int -> ReadS b) -> ReadS [b] -> ReadS [ Either a b] Source # liftReadPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec ( Either a b) Source # liftReadListPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec [ Either a b] Source # |
|
Show2 Either |
Since: base-4.9.0.0 |
Defined in Data.Functor.Classes |
|
NFData2 Either |
Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq |
|
Hashable2 Either | |
Bitraversable1 Either | |
Defined in Data.Semigroup.Traversable.Class |
|
MonadError e ( Either e) | |
Defined in Control.Monad.Error.Class Methods throwError :: e -> Either e a Source # catchError :: Either e a -> (e -> Either e a) -> Either e a Source # |
|
( Lift a, Lift b) => Lift ( Either a b :: Type ) | |
( Typeable DefaultUni a, Typeable DefaultUni b, Lift DefaultUni a, Lift DefaultUni b) => Lift DefaultUni ( Either a b) Source # | |
Defined in PlutusTx.Lift.Instances Methods lift :: Either a b -> RTCompile DefaultUni fun ( Term TyName Name DefaultUni fun ()) Source # |
|
Monad ( Either e) |
Since: base-4.4.0.0 |
Functor ( Either a) |
Since: base-3.0 |
MonadFix ( Either e) |
Since: base-4.3.0.0 |
Applicative ( Either e) |
Since: base-3.0 |
Defined in Data.Either |
|
Foldable ( Either a) |
Since: base-4.7.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => Either a m -> m Source # foldMap :: Monoid m => (a0 -> m) -> Either a a0 -> m Source # foldMap' :: Monoid m => (a0 -> m) -> Either a a0 -> m Source # foldr :: (a0 -> b -> b) -> b -> Either a a0 -> b Source # foldr' :: (a0 -> b -> b) -> b -> Either a a0 -> b Source # foldl :: (b -> a0 -> b) -> b -> Either a a0 -> b Source # foldl' :: (b -> a0 -> b) -> b -> Either a a0 -> b Source # foldr1 :: (a0 -> a0 -> a0) -> Either a a0 -> a0 Source # foldl1 :: (a0 -> a0 -> a0) -> Either a a0 -> a0 Source # toList :: Either a a0 -> [a0] Source # null :: Either a a0 -> Bool Source # length :: Either a a0 -> Int Source # elem :: Eq a0 => a0 -> Either a a0 -> Bool Source # maximum :: Ord a0 => Either a a0 -> a0 Source # minimum :: Ord a0 => Either a a0 -> a0 Source # |
|
Traversable ( Either a) |
Since: base-4.7.0.0 |
Defined in Data.Traversable Methods traverse :: Applicative f => (a0 -> f b) -> Either a a0 -> f ( Either a b) Source # sequenceA :: Applicative f => Either a (f a0) -> f ( Either a a0) Source # mapM :: Monad m => (a0 -> m b) -> Either a a0 -> m ( Either a b) Source # sequence :: Monad m => Either a (m a0) -> m ( Either a a0) Source # |
|
ToJSON a => ToJSON1 ( Either a) | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON :: (a0 -> Value ) -> ([a0] -> Value ) -> Either a a0 -> Value Source # liftToJSONList :: (a0 -> Value ) -> ([a0] -> Value ) -> [ Either a a0] -> Value Source # liftToEncoding :: (a0 -> Encoding ) -> ([a0] -> Encoding ) -> Either a a0 -> Encoding Source # liftToEncodingList :: (a0 -> Encoding ) -> ([a0] -> Encoding ) -> [ Either a a0] -> Encoding Source # |
|
FromJSON a => FromJSON1 ( Either a) | |
Eq a => Eq1 ( Either a) |
Since: base-4.9.0.0 |
Ord a => Ord1 ( Either a) |
Since: base-4.9.0.0 |
Defined in Data.Functor.Classes |
|
Show a => Show1 ( Either a) |
Since: base-4.9.0.0 |
Read a => Read1 ( Either a) |
Since: base-4.9.0.0 |
Defined in Data.Functor.Classes Methods liftReadsPrec :: ( Int -> ReadS a0) -> ReadS [a0] -> Int -> ReadS ( Either a a0) Source # liftReadList :: ( Int -> ReadS a0) -> ReadS [a0] -> ReadS [ Either a a0] Source # liftReadPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec ( Either a a0) Source # liftReadListPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec [ Either a a0] Source # |
|
MonadFailure ( Either a) | |
NFData a => NFData1 ( Either a) |
Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq |
|
Hashable a => Hashable1 ( Either a) | |
Defined in Data.Hashable.Class |
|
Functor ( Either c) Source # | |
Applicative ( Either a) Source # | |
Foldable ( Either c) Source # | |
Traversable ( Either c) Source # | |
Defined in PlutusTx.Traversable |
|
Generic1 ( Either a :: Type -> Type ) |
Since: base-4.6.0.0 |
MonadBaseControl ( Either e) ( Either e) | |
( Eq a, Eq b) => Eq ( Either a b) |
Since: base-2.1 |
( Data a, Data b) => Data ( Either a b) |
Since: base-4.0.0.0 |
Defined in Data.Data Methods gfoldl :: ( forall d b0. Data d => c (d -> b0) -> d -> c b0) -> ( forall g. g -> c g) -> Either a b -> c ( Either a b) Source # gunfold :: ( forall b0 r. Data b0 => c (b0 -> r) -> c r) -> ( forall r. r -> c r) -> Constr -> c ( Either a b) Source # toConstr :: Either a b -> Constr Source # dataTypeOf :: Either a b -> DataType Source # dataCast1 :: Typeable t => ( forall d. Data d => c (t d)) -> Maybe (c ( Either a b)) Source # dataCast2 :: Typeable t => ( forall d e. ( Data d, Data e) => c (t d e)) -> Maybe (c ( Either a b)) Source # gmapT :: ( forall b0. Data b0 => b0 -> b0) -> Either a b -> Either a b Source # gmapQl :: (r -> r' -> r) -> r -> ( forall d. Data d => d -> r') -> Either a b -> r Source # gmapQr :: forall r r'. (r' -> r -> r) -> r -> ( forall d. Data d => d -> r') -> Either a b -> r Source # gmapQ :: ( forall d. Data d => d -> u) -> Either a b -> [u] Source # gmapQi :: Int -> ( forall d. Data d => d -> u) -> Either a b -> u Source # gmapM :: Monad m => ( forall d. Data d => d -> m d) -> Either a b -> m ( Either a b) Source # gmapMp :: MonadPlus m => ( forall d. Data d => d -> m d) -> Either a b -> m ( Either a b) Source # gmapMo :: MonadPlus m => ( forall d. Data d => d -> m d) -> Either a b -> m ( Either a b) Source # |
|
( Ord a, Ord b) => Ord ( Either a b) |
Since: base-2.1 |
Defined in Data.Either Methods compare :: Either a b -> Either a b -> Ordering Source # (<) :: Either a b -> Either a b -> Bool Source # (<=) :: Either a b -> Either a b -> Bool Source # (>) :: Either a b -> Either a b -> Bool Source # (>=) :: Either a b -> Either a b -> Bool Source # |
|
( Read a, Read b) => Read ( Either a b) |
Since: base-3.0 |
( Show a, Show b) => Show ( Either a b) |
Since: base-3.0 |
Generic ( Either a b) |
Since: base-4.6.0.0 |
Semigroup ( Either a b) |
Since: base-4.9.0.0 |
( Hashable a, Hashable b) => Hashable ( Either a b) | |
( ToJSON a, ToJSON b) => ToJSON ( Either a b) | |
( FromJSON a, FromJSON b) => FromJSON ( Either a b) | |
( NFData a, NFData b) => NFData ( Either a b) | |
Defined in Control.DeepSeq |
|
MonoFunctor ( Either a b) | |
MonoFoldable ( Either a b) | |
Defined in Data.MonoTraversable Methods ofoldMap :: Monoid m => ( Element ( Either a b) -> m) -> Either a b -> m Source # ofoldr :: ( Element ( Either a b) -> b0 -> b0) -> b0 -> Either a b -> b0 Source # ofoldl' :: (a0 -> Element ( Either a b) -> a0) -> a0 -> Either a b -> a0 Source # otoList :: Either a b -> [ Element ( Either a b)] Source # oall :: ( Element ( Either a b) -> Bool ) -> Either a b -> Bool Source # oany :: ( Element ( Either a b) -> Bool ) -> Either a b -> Bool Source # onull :: Either a b -> Bool Source # olength :: Either a b -> Int Source # olength64 :: Either a b -> Int64 Source # ocompareLength :: Integral i => Either a b -> i -> Ordering Source # otraverse_ :: Applicative f => ( Element ( Either a b) -> f b0) -> Either a b -> f () Source # ofor_ :: Applicative f => Either a b -> ( Element ( Either a b) -> f b0) -> f () Source # omapM_ :: Applicative m => ( Element ( Either a b) -> m ()) -> Either a b -> m () Source # oforM_ :: Applicative m => Either a b -> ( Element ( Either a b) -> m ()) -> m () Source # ofoldlM :: Monad m => (a0 -> Element ( Either a b) -> m a0) -> a0 -> Either a b -> m a0 Source # ofoldMap1Ex :: Semigroup m => ( Element ( Either a b) -> m) -> Either a b -> m Source # ofoldr1Ex :: ( Element ( Either a b) -> Element ( Either a b) -> Element ( Either a b)) -> Either a b -> Element ( Either a b) Source # ofoldl1Ex' :: ( Element ( Either a b) -> Element ( Either a b) -> Element ( Either a b)) -> Either a b -> Element ( Either a b) Source # headEx :: Either a b -> Element ( Either a b) Source # lastEx :: Either a b -> Element ( Either a b) Source # unsafeHead :: Either a b -> Element ( Either a b) Source # unsafeLast :: Either a b -> Element ( Either a b) Source # maximumByEx :: ( Element ( Either a b) -> Element ( Either a b) -> Ordering ) -> Either a b -> Element ( Either a b) Source # minimumByEx :: ( Element ( Either a b) -> Element ( Either a b) -> Ordering ) -> Either a b -> Element ( Either a b) Source # oelem :: Element ( Either a b) -> Either a b -> Bool Source # onotElem :: Element ( Either a b) -> Either a b -> Bool Source # |
|
MonoTraversable ( Either a b) | |
MonoPointed ( Either a b) | |
Recursive ( Either a b) | |
Defined in Data.Functor.Foldable Methods project :: Either a b -> Base ( Either a b) ( Either a b) Source # cata :: ( Base ( Either a b) a0 -> a0) -> Either a b -> a0 Source # para :: ( Base ( Either a b) ( Either a b, a0) -> a0) -> Either a b -> a0 Source # gpara :: ( Corecursive ( Either a b), Comonad w) => ( forall b0. Base ( Either a b) (w b0) -> w ( Base ( Either a b) b0)) -> ( Base ( Either a b) ( EnvT ( Either a b) w a0) -> a0) -> Either a b -> a0 Source # prepro :: Corecursive ( Either a b) => ( forall b0. Base ( Either a b) b0 -> Base ( Either a b) b0) -> ( Base ( Either a b) a0 -> a0) -> Either a b -> a0 Source # gprepro :: ( Corecursive ( Either a b), Comonad w) => ( forall b0. Base ( Either a b) (w b0) -> w ( Base ( Either a b) b0)) -> ( forall c. Base ( Either a b) c -> Base ( Either a b) c) -> ( Base ( Either a b) (w a0) -> a0) -> Either a b -> a0 Source # |
|
Corecursive ( Either a b) | |
Defined in Data.Functor.Foldable Methods embed :: Base ( Either a b) ( Either a b) -> Either a b Source # ana :: (a0 -> Base ( Either a b) a0) -> a0 -> Either a b Source # apo :: (a0 -> Base ( Either a b) ( Either ( Either a b) a0)) -> a0 -> Either a b Source # postpro :: Recursive ( Either a b) => ( forall b0. Base ( Either a b) b0 -> Base ( Either a b) b0) -> (a0 -> Base ( Either a b) a0) -> a0 -> Either a b Source # gpostpro :: ( Recursive ( Either a b), Monad m) => ( forall b0. m ( Base ( Either a b) b0) -> Base ( Either a b) (m b0)) -> ( forall c. Base ( Either a b) c -> Base ( Either a b) c) -> (a0 -> Base ( Either a b) (m a0)) -> a0 -> Either a b Source # |
|
( Serialise a, Serialise b) => Serialise ( Either a b) |
Since: serialise-0.2.0.0 |
( Eq a, Eq b) => Eq ( Either a b) Source # | |
( Ord a, Ord b) => Ord ( Either a b) Source # | |
Defined in PlutusTx.Ord Methods compare :: Either a b -> Either a b -> Ordering Source # (<) :: Either a b -> Either a b -> Bool Source # (<=) :: Either a b -> Either a b -> Bool Source # (>) :: Either a b -> Either a b -> Bool Source # (>=) :: Either a b -> Either a b -> Bool Source # |
|
( UnsafeFromData a, UnsafeFromData b) => UnsafeFromData ( Either a b) Source # | |
Defined in PlutusTx.IsData.Instances Methods unsafeFromBuiltinData :: BuiltinData -> Either a b Source # |
|
( FromData a, FromData b) => FromData ( Either a b) Source # | |
Defined in PlutusTx.IsData.Instances Methods fromBuiltinData :: BuiltinData -> Maybe ( Either a b) Source # |
|
( ToData a, ToData b) => ToData ( Either a b) Source # | |
Defined in PlutusTx.IsData.Instances Methods toBuiltinData :: Either a b -> BuiltinData Source # |
|
Typeable DefaultUni Either Source # | |
Defined in PlutusTx.Lift.Instances Methods typeRep :: Proxy Either -> RTCompile DefaultUni fun ( Type TyName DefaultUni ()) Source # |
|
(a ~ a', b ~ b') => Each ( Either a a') ( Either b b') a b |
Since: lens-4.18 |
(a ~ a', b ~ b') => Each ( Either a a') ( Either b b') a b |
Since: microlens-0.4.11 |
( FunctorWithIndex i f, FunctorWithIndex j g) => FunctorWithIndex ( Either i j) ( Sum f g) | |
( FunctorWithIndex i f, FunctorWithIndex j g) => FunctorWithIndex ( Either i j) ( Product f g) | |
( FunctorWithIndex i f, FunctorWithIndex j g) => FunctorWithIndex ( Either i j) (f :+: g) | |
( FunctorWithIndex i f, FunctorWithIndex j g) => FunctorWithIndex ( Either i j) (f :*: g) | |
( FoldableWithIndex i f, FoldableWithIndex j g) => FoldableWithIndex ( Either i j) ( Sum f g) | |
Defined in WithIndex Methods ifoldMap :: Monoid m => ( Either i j -> a -> m) -> Sum f g a -> m Source # ifoldMap' :: Monoid m => ( Either i j -> a -> m) -> Sum f g a -> m Source # ifoldr :: ( Either i j -> a -> b -> b) -> b -> Sum f g a -> b Source # ifoldl :: ( Either i j -> b -> a -> b) -> b -> Sum f g a -> b Source # ifoldr' :: ( Either i j -> a -> b -> b) -> b -> Sum f g a -> b Source # ifoldl' :: ( Either i j -> b -> a -> b) -> b -> Sum f g a -> b Source # |
|
( FoldableWithIndex i f, FoldableWithIndex j g) => FoldableWithIndex ( Either i j) ( Product f g) | |
Defined in WithIndex Methods ifoldMap :: Monoid m => ( Either i j -> a -> m) -> Product f g a -> m Source # ifoldMap' :: Monoid m => ( Either i j -> a -> m) -> Product f g a -> m Source # ifoldr :: ( Either i j -> a -> b -> b) -> b -> Product f g a -> b Source # ifoldl :: ( Either i j -> b -> a -> b) -> b -> Product f g a -> b Source # ifoldr' :: ( Either i j -> a -> b -> b) -> b -> Product f g a -> b Source # ifoldl' :: ( Either i j -> b -> a -> b) -> b -> Product f g a -> b Source # |
|
( FoldableWithIndex i f, FoldableWithIndex j g) => FoldableWithIndex ( Either i j) (f :+: g) | |
Defined in WithIndex Methods ifoldMap :: Monoid m => ( Either i j -> a -> m) -> (f :+: g) a -> m Source # ifoldMap' :: Monoid m => ( Either i j -> a -> m) -> (f :+: g) a -> m Source # ifoldr :: ( Either i j -> a -> b -> b) -> b -> (f :+: g) a -> b Source # ifoldl :: ( Either i j -> b -> a -> b) -> b -> (f :+: g) a -> b Source # ifoldr' :: ( Either i j -> a -> b -> b) -> b -> (f :+: g) a -> b Source # ifoldl' :: ( Either i j -> b -> a -> b) -> b -> (f :+: g) a -> b Source # |
|
( FoldableWithIndex i f, FoldableWithIndex j g) => FoldableWithIndex ( Either i j) (f :*: g) | |
Defined in WithIndex Methods ifoldMap :: Monoid m => ( Either i j -> a -> m) -> (f :*: g) a -> m Source # ifoldMap' :: Monoid m => ( Either i j -> a -> m) -> (f :*: g) a -> m Source # ifoldr :: ( Either i j -> a -> b -> b) -> b -> (f :*: g) a -> b Source # ifoldl :: ( Either i j -> b -> a -> b) -> b -> (f :*: g) a -> b Source # ifoldr' :: ( Either i j -> a -> b -> b) -> b -> (f :*: g) a -> b Source # ifoldl' :: ( Either i j -> b -> a -> b) -> b -> (f :*: g) a -> b Source # |
|
( TraversableWithIndex i f, TraversableWithIndex j g) => TraversableWithIndex ( Either i j) ( Sum f g) | |
( TraversableWithIndex i f, TraversableWithIndex j g) => TraversableWithIndex ( Either i j) ( Product f g) | |
( TraversableWithIndex i f, TraversableWithIndex j g) => TraversableWithIndex ( Either i j) (f :+: g) | |
( TraversableWithIndex i f, TraversableWithIndex j g) => TraversableWithIndex ( Either i j) (f :*: g) | |
type Failure ( Either a) | |
Defined in Basement.Monad |
|
type StM ( Either e) a | |
Defined in Control.Monad.Trans.Control |
|
type Rep1 ( Either a :: Type -> Type ) | |
Defined in GHC.Generics
type
Rep1
(
Either
a ::
Type
->
Type
) =
D1
('
MetaData
"Either" "Data.Either" "base" '
False
) (
C1
('
MetaCons
"Left" '
PrefixI
'
False
) (
S1
('
MetaSel
('
Nothing
::
Maybe
Symbol
) '
NoSourceUnpackedness
'
NoSourceStrictness
'
DecidedLazy
) (
Rec0
a))
:+:
C1
('
MetaCons
"Right" '
PrefixI
'
False
) (
S1
('
MetaSel
('
Nothing
::
Maybe
Symbol
) '
NoSourceUnpackedness
'
NoSourceStrictness
'
DecidedLazy
)
Par1
))
|
|
type Rep ( Either a b) | |
Defined in GHC.Generics
type
Rep
(
Either
a b) =
D1
('
MetaData
"Either" "Data.Either" "base" '
False
) (
C1
('
MetaCons
"Left" '
PrefixI
'
False
) (
S1
('
MetaSel
('
Nothing
::
Maybe
Symbol
) '
NoSourceUnpackedness
'
NoSourceStrictness
'
DecidedLazy
) (
Rec0
a))
:+:
C1
('
MetaCons
"Right" '
PrefixI
'
False
) (
S1
('
MetaSel
('
Nothing
::
Maybe
Symbol
) '
NoSourceUnpackedness
'
NoSourceStrictness
'
DecidedLazy
) (
Rec0
b)))
|
|
type Element ( Either a b) | |
Defined in Data.MonoTraversable |
|
type Base ( Either a b) |
Example boring stub for non-recursive data types |