| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell2010 |
Distribution.Compat.Semigroup
Description
Compatibility layer for Data.Semigroup
Synopsis
- class Semigroup a where
- (<>) :: a -> a -> a
- class Semigroup a => Monoid a where
- newtype All = All {}
- newtype Any = Any {}
- newtype First' a = First' {
- getFirst' :: a
- newtype Last' a = Last' {
- getLast' :: a
- newtype Option' a = Option' {
- getOption' :: Maybe a
- gmappend :: (Generic a, GSemigroup (Rep a)) => a -> a -> a
- gmempty :: (Generic a, GMonoid (Rep a)) => a
Documentation
The class of semigroups (types with an associative binary operation).
Instances should satisfy the following:
You can alternatively define sconcat instead of (<>), in which case the
laws are:
Since: base-4.9.0.0
Instances
class Semigroup a => Monoid a where #
The class of monoids (types with an associative binary operation that has an identity). Instances should satisfy the following:
- Right identity
x<>mempty= x- Left identity
mempty<>x = x- Associativity
x(<>(y<>z) = (x<>y)<>zSemigrouplaw)- Concatenation
mconcat=foldr(<>)mempty
You can alternatively define mconcat instead of mempty, in which case the
laws are:
- Unit
mconcat(purex) = x- Multiplication
mconcat(joinxss) =mconcat(fmapmconcatxss)- Subclass
mconcat(toListxs) =sconcatxs
The method names refer to the monoid of lists under concatenation, but there are many other instances.
Some types can be viewed as a monoid in more than one way,
e.g. both addition and multiplication on numbers.
In such cases we often define newtypes and make those instances
of Monoid, e.g. Sum and Product.
NOTE: Semigroup is a superclass of Monoid since base-4.11.0.0.
Methods
Identity of mappend
>>>"Hello world" <> mempty"Hello world"
An associative operation
NOTE: This method is redundant and has the default
implementation mappend = (<>)mappend is a synonym for
(<>), it is expected that the two functions are defined the same
way. In a future GHC release mappend will be removed from Monoid.
Fold a list using the monoid.
For most types, the default definition for mconcat will be
used, but the function is included in the class definition so
that an optimized version can be provided for specific types.
>>>mconcat ["Hello", " ", "Haskell", "!"]"Hello Haskell!"
Instances
Boolean monoid under conjunction (&&).
>>>getAll (All True <> mempty <> All False)False
>>>getAll (mconcat (map (\x -> All (even x)) [2,4,6,7,8]))False
Instances
| Data All | Since: base-4.8.0.0 |
Defined in Data.Data Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> All -> c All # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c All # dataTypeOf :: All -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c All) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c All) # gmapT :: (forall b. Data b => b -> b) -> All -> All # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> All -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> All -> r # gmapQ :: (forall d. Data d => d -> u) -> All -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> All -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> All -> m All # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> All -> m All # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> All -> m All # | |
| Monoid All | Since: base-2.1 |
| Semigroup All | Since: base-4.9.0.0 |
| Bounded All | Since: base-2.1 |
| Generic All | |
| Read All | Since: base-2.1 |
| Show All | Since: base-2.1 |
| Binary All | Since: binary-0.8.4.0 |
| NFData All | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
| Eq All | Since: base-2.1 |
| Ord All | Since: base-2.1 |
| type Rep All | Since: base-4.7.0.0 |
Defined in Data.Semigroup.Internal | |
Boolean monoid under disjunction (||).
>>>getAny (Any True <> mempty <> Any False)True
>>>getAny (mconcat (map (\x -> Any (even x)) [2,4,6,7,8]))True
Instances
| Data Any | Since: base-4.8.0.0 |
Defined in Data.Data Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Any -> c Any # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Any # dataTypeOf :: Any -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Any) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Any) # gmapT :: (forall b. Data b => b -> b) -> Any -> Any # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Any -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Any -> r # gmapQ :: (forall d. Data d => d -> u) -> Any -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Any -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Any -> m Any # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Any -> m Any # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Any -> m Any # | |
| Monoid Any | Since: base-2.1 |
| Semigroup Any | Since: base-4.9.0.0 |
| Bounded Any | Since: base-2.1 |
| Generic Any | |
| Read Any | Since: base-2.1 |
| Show Any | Since: base-2.1 |
| Binary Any | Since: binary-0.8.4.0 |
| NFData Any | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
| Eq Any | Since: base-2.1 |
| Ord Any | Since: base-2.1 |
| type Rep Any | Since: base-4.7.0.0 |
Defined in Data.Semigroup.Internal | |
A copy of First.
A copy of Last.
Instances
| Functor Last' Source # | |
| Structured a => Structured (Last' a) Source # | |
Defined in Distribution.Compat.Semigroup | |
| Semigroup (Last' a) Source # | |
| Generic (Last' a) Source # | |
| Read a => Read (Last' a) Source # | |
| Show a => Show (Last' a) Source # | |
| Binary a => Binary (Last' a) Source # | |
| Eq a => Eq (Last' a) Source # | |
| Ord a => Ord (Last' a) Source # | |
Defined in Distribution.Compat.Semigroup | |
| type Rep (Last' a) Source # | |
Defined in Distribution.Compat.Semigroup | |
A wrapper around Maybe, providing the Semigroup and Monoid instances
implemented for Maybe since base-4.11.
Constructors
| Option' | |
Fields
| |
Instances
| Functor Option' Source # | |
| Structured a => Structured (Option' a) Source # | |
Defined in Distribution.Compat.Semigroup | |
| Semigroup a => Monoid (Option' a) Source # | |
| Semigroup a => Semigroup (Option' a) Source # | |
| Generic (Option' a) Source # | |
| Read a => Read (Option' a) Source # | |
| Show a => Show (Option' a) Source # | |
| Binary a => Binary (Option' a) Source # | |
| Eq a => Eq (Option' a) Source # | |
| Ord a => Ord (Option' a) Source # | |
| type Rep (Option' a) Source # | |
Defined in Distribution.Compat.Semigroup | |