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) -> {- ... -}Instances9Functor, Eq, Data, Ord, Read, Show, …
Functor OnlyDefined in Only-0.1 · Data.Tuple.OnlyEq a => Eq (Only a)Defined in Only-0.1 · Data.Tuple.OnlyData a => Data (Only a)Defined in Only-0.1 · Data.Tuple.OnlyOrd a => Ord (Only a)Defined in Only-0.1 · Data.Tuple.OnlyRead a => Read (Only a)Defined in Only-0.1 · Data.Tuple.OnlyShow a => Show (Only a)Defined in Only-0.1 · Data.Tuple.OnlyGeneric (Only a)Defined in Only-0.1 · Data.Tuple.OnlyNFData a => NFData (Only a)Defined in Only-0.1 · Data.Tuple.Onlytype Rep (Only a) = D1 ('MetaDataDefined in Only-0.1 · Data.Tuple.Only"Only"
"Data.Tuple.Only"
"Only-0.1-8BKwq0wmUnbJYtB6F6W6xk"
'True) (C1 ('MetaCons"Only"
'PrefixI 'True) (S1 ('MetaSel ('Just"fromOnly"
) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))