Data.Tuple.Only

Only-0.1: The 1-tuple type or single-value "collection"

Safe Haskell | Safe
Language | Haskell2010

Data.Tuple.Only

Synopsis

- newtype Only a = Only {
  - fromOnly :: a
  }

# Documentation

newtype Only a #

The 1-tuple type or single-value "collection".

This type is structurally equivalent to the `Identity` type, but its intent is more about serving as the anonymous 1-tuple type missing from Haskell for attaching typeclass instances.

Parameter usage example:

    encodeSomething (Only (42::Int))

Result usage example:

    xs <- decodeSomething
    forM_ xs $ \(Only id) -> {- ... -}

Constructors

Only |
Fields fromOnly :: a

#### Instances

Instances details

Functor Only # |
Instance details Defined in Data.Tuple.Only Methods fmap :: (a -> b) -> Only a -> Only b # (<$) :: a -> Only b -> Only a #
NFData a => NFData (Only a) # |
Instance details Defined in Data.Tuple.Only Methods rnf :: Only a -> () #
Data a => Data (Only a) # |
Instance details Defined in Data.Tuple.Only Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Only a -> c (Only a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Only a) # toConstr :: Only a -> Constr # dataTypeOf :: Only a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Only a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Only a)) # gmapT :: (forall b. Data b => b -> b) -> Only a -> Only a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Only a -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Only a -> r # gmapQ :: (forall d. Data d => d -> u) -> Only a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Only a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Only a -> m (Only a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Only a -> m (Only a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Only a -> m (Only a) #
Generic (Only a) # |
Instance details Defined in Data.Tuple.Only Associated Types
type Rep (Only a) |
Instance details Defined in Data.Tuple.Only type Rep (Only a) = D1 ('MetaData "Only" "Data.Tuple.Only" "Only-0.1-1vWhUvIywEwKH1HtIRFVaX" 'True) (C1 ('MetaCons "Only" 'PrefixI 'True) (S1 ('MetaSel ('Just "fromOnly") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))
Methods from :: Only a -> Rep (Only a) x # to :: Rep (Only a) x -> Only a #
Read a => Read (Only a) # |
Instance details Defined in Data.Tuple.Only Methods readsPrec :: Int -> ReadS (Only a) # readList :: ReadS [Only a] # readPrec :: ReadPrec (Only a) # readListPrec :: ReadPrec [Only a] #
Show a => Show (Only a) # |
Instance details Defined in Data.Tuple.Only Methods showsPrec :: Int -> Only a -> ShowS # show :: Only a -> String # showList :: [Only a] -> ShowS #
Eq a => Eq (Only a) # |
Instance details Defined in Data.Tuple.Only Methods (==) :: Only a -> Only a -> Bool # (/=) :: Only a -> Only a -> Bool #
Ord a => Ord (Only a) # |
Instance details Defined in Data.Tuple.Only Methods compare :: Only a -> Only a -> Ordering # (<) :: Only a -> Only a -> Bool # (<=) :: Only a -> Only a -> Bool # (>) :: Only a -> Only a -> Bool # (>=) :: Only a -> Only a -> Bool # max :: Only a -> Only a -> Only a # min :: Only a -> Only a -> Only a #
type Rep (Only a) # |
Instance details Defined in Data.Tuple.Only type Rep (Only a) = D1 ('MetaData "Only" "Data.Tuple.Only" "Only-0.1-1vWhUvIywEwKH1HtIRFVaX" 'True) (C1 ('MetaCons "Only" 'PrefixI 'True) (S1 ('MetaSel ('Just "fromOnly") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))