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Data.Semigroup
Copyright | (C) 2011-2015 Edward Kmett |
---|---|
License | BSD-style (see the file LICENSE) |
Maintainer | libraries@haskell.org |
Stability | provisional |
Portability | portable |
Safe Haskell | Trustworthy |
Language | Haskell2010 |
Description
A type a
is a Semigroup
if it provides an associative function (<>
) that lets you combine any two values of type a
into one. Where being associative means that the following must always hold:
(a <> b) <> c == a <> (b <> c)
Examples
The Min
Semigroup
instance for Int
is defined to always pick the smaller number: >>> Min 1 <> Min 2 <> Min 3 <> Min 4 :: Min Int Min {getMin = 1}
If we need to combine multiple values we can use the sconcat
function to do so. We need to ensure however that we have at least one value to operate on, since otherwise our result would be undefined. It is for this reason that sconcat
uses Data.List.NonEmpty.NonEmpty - a list that can never be empty:
>>> (1 :| [])
1 :| [] -- equivalent to [1] but guaranteed to be non-empty.
>>> (1 :| [2, 3, 4])
1 :| [2,3,4] -- equivalent to [1,2,3,4] but guaranteed to be non-empty.
Equipped with this guaranteed to be non-empty data structure, we can combine values using sconcat
and a Semigroup
of our choosing. We can try the Min
and Max
instances of Int
which pick the smallest, or largest number respectively:
>>> sconcat (1 :| [2, 3, 4]) :: Min Int
Min {getMin = 1}
>>> sconcat (1 :| [2, 3, 4]) :: Max Int
Max {getMax = 4}
String concatenation is another example of a Semigroup
instance:
>>> "foo" <> "bar"
"foobar"
A Semigroup
is a generalization of a Monoid
. Yet unlike the Semigroup
, the Monoid
requires the presence of a neutral element (mempty
) in addition to the associative operator. The requirement for a neutral element prevents many types from being a full Monoid, like Data.List.NonEmpty.NonEmpty.
Note that the use of (<>)
in this module conflicts with an operator with the same name that is being exported by Data.Monoid. However, this package re-exports (most of) the contents of Data.Monoid, so to use semigroups and monoids in the same package just
import Data.Semigroup
Since: base-4.9.0.0
class Semigroup a where Source
The class of semigroups (types with an associative binary operation).
Instances should satisfy the following:
Since: base-4.9.0.0
Minimal complete definition
Methods
(<>) :: a -> a -> a infixr 6 Source
An associative operation.
>>> [1,2,3] <> [4,5,6]
[1,2,3,4,5,6]
sconcat :: NonEmpty a -> a Source
Reduce a non-empty list with <>
The default definition should be sufficient, but this can be overridden for efficiency.
>>> import Data.List.NonEmpty (NonEmpty (..))
>>> sconcat $ "Hello" :| [" ", "Haskell", "!"]
"Hello Haskell!"
stimes :: Integral b => b -> a -> a Source
Repeat a value n
times.
Given that this works on a Semigroup
it is allowed to fail if you request 0 or fewer repetitions, and the default definition will do so.
By making this a member of the class, idempotent semigroups and monoids can upgrade this to execute in \(\mathcal{O}(1)\) by picking stimes = stimesIdempotent
or stimes = stimesIdempotentMonoid
respectively.
>>> stimes 4 [1]
[1,1,1,1]
Instances
Semigroup ByteArray Source | Since: base-4.17.0.0 |
Semigroup All Source | Since: base-4.9.0.0 |
Semigroup Any Source | Since: base-4.9.0.0 |
Semigroup Void Source | Since: base-4.9.0.0 |
Semigroup Event Source | Since: base-4.10.0.0 |
Semigroup Lifetime Source | Since: base-4.10.0.0 |
Semigroup Ordering Source | Since: base-4.9.0.0 |
Semigroup () Source | Since: base-4.9.0.0 |
Bits a => Semigroup (And a) Source | Since: base-4.16 |
FiniteBits a => Semigroup (Iff a) Source | This constraint is arguably too strong. However, as some types (such as Since: base-4.16 |
Bits a => Semigroup (Ior a) Source | Since: base-4.16 |
Bits a => Semigroup (Xor a) Source | Since: base-4.16 |
Semigroup (Comparison a) Source |
|
Defined in Data.Functor.Contravariant Methods(<>) :: Comparison a -> Comparison a -> Comparison a Source sconcat :: NonEmpty (Comparison a) -> Comparison a Source stimes :: Integral b => b -> Comparison a -> Comparison a Source |
|
Semigroup (Equivalence a) Source |
|
Defined in Data.Functor.Contravariant Methods(<>) :: Equivalence a -> Equivalence a -> Equivalence a Source sconcat :: NonEmpty (Equivalence a) -> Equivalence a Source stimes :: Integral b => b -> Equivalence a -> Equivalence a Source |
|
Semigroup (Predicate a) Source |
|
Semigroup a => Semigroup (Identity a) Source | Since: base-4.9.0.0 |
Semigroup (First a) Source | Since: base-4.9.0.0 |
Semigroup (Last a) Source | Since: base-4.9.0.0 |
Semigroup a => Semigroup (Down a) Source | Since: base-4.11.0.0 |
Semigroup (First a) Source | Since: base-4.9.0.0 |
Semigroup (Last a) Source | Since: base-4.9.0.0 |
Ord a => Semigroup (Max a) Source | Since: base-4.9.0.0 |
Ord a => Semigroup (Min a) Source | Since: base-4.9.0.0 |
Monoid m => Semigroup (WrappedMonoid m) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methods(<>) :: WrappedMonoid m -> WrappedMonoid m -> WrappedMonoid m Source sconcat :: NonEmpty (WrappedMonoid m) -> WrappedMonoid m Source stimes :: Integral b => b -> WrappedMonoid m -> WrappedMonoid m Source |
|
Semigroup a => Semigroup (Dual a) Source | Since: base-4.9.0.0 |
Semigroup (Endo a) Source | Since: base-4.9.0.0 |
Num a => Semigroup (Product a) Source | Since: base-4.9.0.0 |
Num a => Semigroup (Sum a) Source | Since: base-4.9.0.0 |
Semigroup a => Semigroup (STM a) Source | Since: base-4.17.0.0 |
(Generic a, Semigroup (Rep a ())) => Semigroup (Generically a) Source | Since: base-4.17.0.0 |
Defined in GHC.Generics Methods(<>) :: Generically a -> Generically a -> Generically a Source sconcat :: NonEmpty (Generically a) -> Generically a Source stimes :: Integral b => b -> Generically a -> Generically a Source |
|
Semigroup p => Semigroup (Par1 p) Source | Since: base-4.12.0.0 |
Semigroup a => Semigroup (IO a) Source | Since: base-4.10.0.0 |
Semigroup (NonEmpty a) Source | Since: base-4.9.0.0 |
Semigroup a => Semigroup (Maybe a) Source | Since: base-4.9.0.0 |
Semigroup a => Semigroup (a) Source | Since: base-4.15 |
Semigroup [a] Source | Since: base-4.9.0.0 |
Semigroup (Either a b) Source | Since: base-4.9.0.0 |
Semigroup a => Semigroup (Op a b) Source |
|
Semigroup (Proxy s) Source | Since: base-4.9.0.0 |
Semigroup (U1 p) Source | Since: base-4.12.0.0 |
Semigroup (V1 p) Source | Since: base-4.12.0.0 |
Semigroup a => Semigroup (ST s a) Source | Since: base-4.11.0.0 |
Semigroup b => Semigroup (a -> b) Source | Since: base-4.9.0.0 |
(Semigroup a, Semigroup b) => Semigroup (a, b) Source | Since: base-4.9.0.0 |
Semigroup a => Semigroup (Const a b) Source | Since: base-4.9.0.0 |
(Applicative f, Semigroup a) => Semigroup (Ap f a) Source | Since: base-4.12.0.0 |
Alternative f => Semigroup (Alt f a) Source | Since: base-4.9.0.0 |
Semigroup (f p) => Semigroup (Rec1 f p) Source | Since: base-4.12.0.0 |
(Semigroup a, Semigroup b, Semigroup c) => Semigroup (a, b, c) Source | Since: base-4.9.0.0 |
(Semigroup (f a), Semigroup (g a)) => Semigroup (Product f g a) Source | Since: base-4.16.0.0 |
(Semigroup (f p), Semigroup (g p)) => Semigroup ((f :*: g) p) Source | Since: base-4.12.0.0 |
Semigroup c => Semigroup (K1 i c p) Source | Since: base-4.12.0.0 |
(Semigroup a, Semigroup b, Semigroup c, Semigroup d) => Semigroup (a, b, c, d) Source | Since: base-4.9.0.0 |
Semigroup (f (g a)) => Semigroup (Compose f g a) Source | Since: base-4.16.0.0 |
Semigroup (f (g p)) => Semigroup ((f :.: g) p) Source | Since: base-4.12.0.0 |
Semigroup (f p) => Semigroup (M1 i c f p) Source | Since: base-4.12.0.0 |
(Semigroup a, Semigroup b, Semigroup c, Semigroup d, Semigroup e) => Semigroup (a, b, c, d, e) Source | Since: base-4.9.0.0 |
stimesMonoid :: (Integral b, Monoid a) => b -> a -> a Source
This is a valid definition of stimes
for a Monoid
.
Unlike the default definition of stimes
, it is defined for 0 and so it should be preferred where possible.
stimesIdempotent :: Integral b => b -> a -> a Source
This is a valid definition of stimes
for an idempotent Semigroup
.
When x <> x = x
, this definition should be preferred, because it works in \(\mathcal{O}(1)\) rather than \(\mathcal{O}(\log n)\).
stimesIdempotentMonoid :: (Integral b, Monoid a) => b -> a -> a Source
This is a valid definition of stimes
for an idempotent Monoid
.
When mappend x x = x
, this definition should be preferred, because it works in \(\mathcal{O}(1)\) rather than \(\mathcal{O}(\log n)\)
mtimesDefault :: (Integral b, Monoid a) => b -> a -> a Source
Repeat a value n
times.
mtimesDefault n a = a <> a <> ... <> a -- using <> (n-1) times
In many cases, `stimes 0 a` for a Monoid
will produce mempty
. However, there are situations when it cannot do so. In particular, the following situation is fairly common:
data T a = ...
class Constraint1 a
class Constraint1 a => Constraint2 a
instance Constraint1 a => Semigroup
(T a) instance Constraint2 a => Monoid
(T a) @
Since Constraint1
is insufficient to implement mempty
, stimes
for T a
cannot do so.
When working with such a type, or when working polymorphically with Semigroup
instances, mtimesDefault
should be used when the multiplier might be zero. It is implemented using stimes
when the multiplier is nonzero and mempty
when it is zero.
Semigroups
Instances
MonadFix Min Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
|
Foldable Min Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodsfold :: Monoid m => Min m -> m Source foldMap :: Monoid m => (a -> m) -> Min a -> m Source foldMap' :: Monoid m => (a -> m) -> Min a -> m Source foldr :: (a -> b -> b) -> b -> Min a -> b Source foldr' :: (a -> b -> b) -> b -> Min a -> b Source foldl :: (b -> a -> b) -> b -> Min a -> b Source foldl' :: (b -> a -> b) -> b -> Min a -> b Source foldr1 :: (a -> a -> a) -> Min a -> a Source foldl1 :: (a -> a -> a) -> Min a -> a Source elem :: Eq a => a -> Min a -> Bool Source maximum :: Ord a => Min a -> a Source minimum :: Ord a => Min a -> a Source |
|
Traversable Min Source | Since: base-4.9.0.0 |
Applicative Min Source | Since: base-4.9.0.0 |
Functor Min Source | Since: base-4.9.0.0 |
Monad Min Source | Since: base-4.9.0.0 |
Generic1 Min Source | |
Data a => Data (Min a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodsgfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Min a -> c (Min a) Source gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Min a) Source toConstr :: Min a -> Constr Source dataTypeOf :: Min a -> DataType Source dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Min a)) Source dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Min a)) Source gmapT :: (forall b. Data b => b -> b) -> Min a -> Min a Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Min a -> r Source gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Min a -> r Source gmapQ :: (forall d. Data d => d -> u) -> Min a -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> Min a -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> Min a -> m (Min a) Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Min a -> m (Min a) Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Min a -> m (Min a) Source |
|
(Ord a, Bounded a) => Monoid (Min a) Source | Since: base-4.9.0.0 |
Ord a => Semigroup (Min a) Source | Since: base-4.9.0.0 |
Bounded a => Bounded (Min a) Source | Since: base-4.9.0.0 |
Enum a => Enum (Min a) Source | Since: base-4.9.0.0 |
Generic (Min a) Source | |
Num a => Num (Min a) Source | Since: base-4.9.0.0 |
Read a => Read (Min a) Source | Since: base-4.9.0.0 |
Show a => Show (Min a) Source | Since: base-4.9.0.0 |
Eq a => Eq (Min a) Source | Since: base-4.9.0.0 |
Ord a => Ord (Min a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
|
type Rep1 Min Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
|
type Rep (Min a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
Instances
MonadFix Max Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
|
Foldable Max Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodsfold :: Monoid m => Max m -> m Source foldMap :: Monoid m => (a -> m) -> Max a -> m Source foldMap' :: Monoid m => (a -> m) -> Max a -> m Source foldr :: (a -> b -> b) -> b -> Max a -> b Source foldr' :: (a -> b -> b) -> b -> Max a -> b Source foldl :: (b -> a -> b) -> b -> Max a -> b Source foldl' :: (b -> a -> b) -> b -> Max a -> b Source foldr1 :: (a -> a -> a) -> Max a -> a Source foldl1 :: (a -> a -> a) -> Max a -> a Source elem :: Eq a => a -> Max a -> Bool Source maximum :: Ord a => Max a -> a Source minimum :: Ord a => Max a -> a Source |
|
Traversable Max Source | Since: base-4.9.0.0 |
Applicative Max Source | Since: base-4.9.0.0 |
Functor Max Source | Since: base-4.9.0.0 |
Monad Max Source | Since: base-4.9.0.0 |
Generic1 Max Source | |
Data a => Data (Max a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodsgfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Max a -> c (Max a) Source gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Max a) Source toConstr :: Max a -> Constr Source dataTypeOf :: Max a -> DataType Source dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Max a)) Source dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Max a)) Source gmapT :: (forall b. Data b => b -> b) -> Max a -> Max a Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Max a -> r Source gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Max a -> r Source gmapQ :: (forall d. Data d => d -> u) -> Max a -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> Max a -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> Max a -> m (Max a) Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Max a -> m (Max a) Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Max a -> m (Max a) Source |
|
(Ord a, Bounded a) => Monoid (Max a) Source | Since: base-4.9.0.0 |
Ord a => Semigroup (Max a) Source | Since: base-4.9.0.0 |
Bounded a => Bounded (Max a) Source | Since: base-4.9.0.0 |
Enum a => Enum (Max a) Source | Since: base-4.9.0.0 |
Generic (Max a) Source | |
Num a => Num (Max a) Source | Since: base-4.9.0.0 |
Read a => Read (Max a) Source | Since: base-4.9.0.0 |
Show a => Show (Max a) Source | Since: base-4.9.0.0 |
Eq a => Eq (Max a) Source | Since: base-4.9.0.0 |
Ord a => Ord (Max a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
|
type Rep1 Max Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
|
type Rep (Max a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
Instances
MonadFix First Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
|
Foldable First Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodsfold :: Monoid m => First m -> m Source foldMap :: Monoid m => (a -> m) -> First a -> m Source foldMap' :: Monoid m => (a -> m) -> First a -> m Source foldr :: (a -> b -> b) -> b -> First a -> b Source foldr' :: (a -> b -> b) -> b -> First a -> b Source foldl :: (b -> a -> b) -> b -> First a -> b Source foldl' :: (b -> a -> b) -> b -> First a -> b Source foldr1 :: (a -> a -> a) -> First a -> a Source foldl1 :: (a -> a -> a) -> First a -> a Source toList :: First a -> [a] Source null :: First a -> Bool Source length :: First a -> Int Source elem :: Eq a => a -> First a -> Bool Source maximum :: Ord a => First a -> a Source minimum :: Ord a => First a -> a Source |
|
Traversable First Source | Since: base-4.9.0.0 |
Applicative First Source | Since: base-4.9.0.0 |
Functor First Source | Since: base-4.9.0.0 |
Monad First Source | Since: base-4.9.0.0 |
Generic1 First Source | |
Data a => Data (First a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodsgfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> First a -> c (First a) Source gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (First a) Source toConstr :: First a -> Constr Source dataTypeOf :: First a -> DataType Source dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (First a)) Source dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (First a)) Source gmapT :: (forall b. Data b => b -> b) -> First a -> First a Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> First a -> r Source gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> First a -> r Source gmapQ :: (forall d. Data d => d -> u) -> First a -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> First a -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> First a -> m (First a) Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> First a -> m (First a) Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> First a -> m (First a) Source |
|
Semigroup (First a) Source | Since: base-4.9.0.0 |
Bounded a => Bounded (First a) Source | Since: base-4.9.0.0 |
Enum a => Enum (First a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodssucc :: First a -> First a Source pred :: First a -> First a Source toEnum :: Int -> First a Source fromEnum :: First a -> Int Source enumFrom :: First a -> [First a] Source enumFromThen :: First a -> First a -> [First a] Source enumFromTo :: First a -> First a -> [First a] Source enumFromThenTo :: First a -> First a -> First a -> [First a] Source |
|
Generic (First a) Source | |
Read a => Read (First a) Source | Since: base-4.9.0.0 |
Show a => Show (First a) Source | Since: base-4.9.0.0 |
Eq a => Eq (First a) Source | Since: base-4.9.0.0 |
Ord a => Ord (First a) Source | Since: base-4.9.0.0 |
type Rep1 First Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
|
type Rep (First a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
Instances
MonadFix Last Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
|
Foldable Last Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodsfold :: Monoid m => Last m -> m Source foldMap :: Monoid m => (a -> m) -> Last a -> m Source foldMap' :: Monoid m => (a -> m) -> Last a -> m Source foldr :: (a -> b -> b) -> b -> Last a -> b Source foldr' :: (a -> b -> b) -> b -> Last a -> b Source foldl :: (b -> a -> b) -> b -> Last a -> b Source foldl' :: (b -> a -> b) -> b -> Last a -> b Source foldr1 :: (a -> a -> a) -> Last a -> a Source foldl1 :: (a -> a -> a) -> Last a -> a Source toList :: Last a -> [a] Source length :: Last a -> Int Source elem :: Eq a => a -> Last a -> Bool Source maximum :: Ord a => Last a -> a Source minimum :: Ord a => Last a -> a Source |
|
Traversable Last Source | Since: base-4.9.0.0 |
Applicative Last Source | Since: base-4.9.0.0 |
Functor Last Source | Since: base-4.9.0.0 |
Monad Last Source | Since: base-4.9.0.0 |
Generic1 Last Source | |
Data a => Data (Last a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodsgfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Last a -> c (Last a) Source gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Last a) Source toConstr :: Last a -> Constr Source dataTypeOf :: Last a -> DataType Source dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Last a)) Source dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Last a)) Source gmapT :: (forall b. Data b => b -> b) -> Last a -> Last a Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Last a -> r Source gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Last a -> r Source gmapQ :: (forall d. Data d => d -> u) -> Last a -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> Last a -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> Last a -> m (Last a) Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Last a -> m (Last a) Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Last a -> m (Last a) Source |
|
Semigroup (Last a) Source | Since: base-4.9.0.0 |
Bounded a => Bounded (Last a) Source | Since: base-4.9.0.0 |
Enum a => Enum (Last a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodssucc :: Last a -> Last a Source pred :: Last a -> Last a Source toEnum :: Int -> Last a Source fromEnum :: Last a -> Int Source enumFrom :: Last a -> [Last a] Source enumFromThen :: Last a -> Last a -> [Last a] Source enumFromTo :: Last a -> Last a -> [Last a] Source enumFromThenTo :: Last a -> Last a -> Last a -> [Last a] Source |
|
Generic (Last a) Source | |
Read a => Read (Last a) Source | Since: base-4.9.0.0 |
Show a => Show (Last a) Source | Since: base-4.9.0.0 |
Eq a => Eq (Last a) Source | Since: base-4.9.0.0 |
Ord a => Ord (Last a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
|
type Rep1 Last Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
|
type Rep (Last a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup |
newtype WrappedMonoid m Source
Provide a Semigroup for an arbitrary Monoid.
NOTE: This is not needed anymore since Semigroup
became a superclass of Monoid
in base-4.11 and this newtype be deprecated at some point in the future.
Constructors
WrapMonoid | |
Fields
|
Instances
Re-exported monoids from Data.Monoid
The dual of a Monoid
, obtained by swapping the arguments of mappend
.
>>> getDual (mappend (Dual "Hello") (Dual "World"))
"WorldHello"
Instances
MonadFix Dual Source | Since: base-4.8.0.0 |
Defined in Control.Monad.Fix |
|
MonadZip Dual Source | Since: base-4.8.0.0 |
Foldable Dual Source | Since: base-4.8.0.0 |
Defined in Data.Foldable Methodsfold :: Monoid m => Dual m -> m Source foldMap :: Monoid m => (a -> m) -> Dual a -> m Source foldMap' :: Monoid m => (a -> m) -> Dual a -> m Source foldr :: (a -> b -> b) -> b -> Dual a -> b Source foldr' :: (a -> b -> b) -> b -> Dual a -> b Source foldl :: (b -> a -> b) -> b -> Dual a -> b Source foldl' :: (b -> a -> b) -> b -> Dual a -> b Source foldr1 :: (a -> a -> a) -> Dual a -> a Source foldl1 :: (a -> a -> a) -> Dual a -> a Source toList :: Dual a -> [a] Source length :: Dual a -> Int Source elem :: Eq a => a -> Dual a -> Bool Source maximum :: Ord a => Dual a -> a Source minimum :: Ord a => Dual a -> a Source |
|
Traversable Dual Source | Since: base-4.8.0.0 |
Applicative Dual Source | Since: base-4.8.0.0 |
Functor Dual Source | Since: base-4.8.0.0 |
Monad Dual Source | Since: base-4.8.0.0 |
Generic1 Dual Source | |
Data a => Data (Dual a) Source | Since: base-4.8.0.0 |
Defined in Data.Data Methodsgfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Dual a -> c (Dual a) Source gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Dual a) Source toConstr :: Dual a -> Constr Source dataTypeOf :: Dual a -> DataType Source dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Dual a)) Source dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Dual a)) Source gmapT :: (forall b. Data b => b -> b) -> Dual a -> Dual a Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Dual a -> r Source gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Dual a -> r Source gmapQ :: (forall d. Data d => d -> u) -> Dual a -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> Dual a -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> Dual a -> m (Dual a) Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Dual a -> m (Dual a) Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Dual a -> m (Dual a) Source |
|
Monoid a => Monoid (Dual a) Source | Since: base-2.1 |
Semigroup a => Semigroup (Dual a) Source | Since: base-4.9.0.0 |
Bounded a => Bounded (Dual a) Source | Since: base-2.1 |
Generic (Dual a) Source | |
Read a => Read (Dual a) Source | Since: base-2.1 |
Show a => Show (Dual a) Source | Since: base-2.1 |
Eq a => Eq (Dual a) Source | Since: base-2.1 |
Ord a => Ord (Dual a) Source | Since: base-2.1 |
Defined in Data.Semigroup.Internal |
|
type Rep1 Dual Source | Since: base-4.7.0.0 |
Defined in Data.Semigroup.Internal |
|
type Rep (Dual a) Source | Since: base-4.7.0.0 |
Defined in Data.Semigroup.Internal |
The monoid of endomorphisms under composition.
>>> let computation = Endo ("Hello, " ++) <> Endo (++ "!")
>>> appEndo computation "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 Source | Since: base-4.8.0.0 |
Defined in Data.Data Methodsgfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> All -> c All Source gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c All Source toConstr :: All -> Constr Source dataTypeOf :: All -> DataType Source dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c All) Source dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c All) Source gmapT :: (forall b. Data b => b -> b) -> All -> All Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> All -> r Source gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> All -> r Source gmapQ :: (forall d. Data d => d -> u) -> All -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> All -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> All -> m All Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> All -> m All Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> All -> m All Source |
|
Monoid All Source | Since: base-2.1 |
Semigroup All Source | Since: base-4.9.0.0 |
Bounded All Source | Since: base-2.1 |
Generic All Source | |
Read All Source | Since: base-2.1 |
Show All Source | Since: base-2.1 |
Eq All Source | Since: base-2.1 |
Ord All Source | Since: base-2.1 |
type Rep All Source | 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 Source | Since: base-4.8.0.0 |
Defined in Data.Data Methodsgfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Any -> c Any Source gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Any Source toConstr :: Any -> Constr Source dataTypeOf :: Any -> DataType Source dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Any) Source dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Any) Source gmapT :: (forall b. Data b => b -> b) -> Any -> Any Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Any -> r Source gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Any -> r Source gmapQ :: (forall d. Data d => d -> u) -> Any -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> Any -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> Any -> m Any Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Any -> m Any Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Any -> m Any Source |
|
Monoid Any Source | Since: base-2.1 |
Semigroup Any Source | Since: base-4.9.0.0 |
Bounded Any Source | Since: base-2.1 |
Generic Any Source | |
Read Any Source | Since: base-2.1 |
Show Any Source | Since: base-2.1 |
Eq Any Source | Since: base-2.1 |
Ord Any Source | Since: base-2.1 |
type Rep Any Source | Since: base-4.7.0.0 |
Defined in Data.Semigroup.Internal |
Monoid under addition.
>>> getSum (Sum 1 <> Sum 2 <> mempty)
3
Instances
MonadFix Sum Source | Since: base-4.8.0.0 |
Defined in Control.Monad.Fix |
|
MonadZip Sum Source | Since: base-4.8.0.0 |
Foldable Sum Source | Since: base-4.8.0.0 |
Defined in Data.Foldable Methodsfold :: Monoid m => Sum m -> m Source foldMap :: Monoid m => (a -> m) -> Sum a -> m Source foldMap' :: Monoid m => (a -> m) -> Sum a -> m Source foldr :: (a -> b -> b) -> b -> Sum a -> b Source foldr' :: (a -> b -> b) -> b -> Sum a -> b Source foldl :: (b -> a -> b) -> b -> Sum a -> b Source foldl' :: (b -> a -> b) -> b -> Sum a -> b Source foldr1 :: (a -> a -> a) -> Sum a -> a Source foldl1 :: (a -> a -> a) -> Sum a -> a Source elem :: Eq a => a -> Sum a -> Bool Source maximum :: Ord a => Sum a -> a Source minimum :: Ord a => Sum a -> a Source |
|
Traversable Sum Source | Since: base-4.8.0.0 |
Applicative Sum Source | Since: base-4.8.0.0 |
Functor Sum Source | Since: base-4.8.0.0 |
Monad Sum Source | Since: base-4.8.0.0 |
Generic1 Sum Source | |
Data a => Data (Sum a) Source | Since: base-4.8.0.0 |
Defined in Data.Data Methodsgfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Sum a -> c (Sum a) Source gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Sum a) Source toConstr :: Sum a -> Constr Source dataTypeOf :: Sum a -> DataType Source dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Sum a)) Source dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Sum a)) Source gmapT :: (forall b. Data b => b -> b) -> Sum a -> Sum a Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Sum a -> r Source gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Sum a -> r Source gmapQ :: (forall d. Data d => d -> u) -> Sum a -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> Sum a -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> Sum a -> m (Sum a) Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Sum a -> m (Sum a) Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Sum a -> m (Sum a) Source |
|
Num a => Monoid (Sum a) Source | Since: base-2.1 |
Num a => Semigroup (Sum a) Source | Since: base-4.9.0.0 |
Bounded a => Bounded (Sum a) Source | Since: base-2.1 |
Generic (Sum a) Source | |
Num a => Num (Sum a) Source | Since: base-4.7.0.0 |
Read a => Read (Sum a) Source | Since: base-2.1 |
Show a => Show (Sum a) Source | Since: base-2.1 |
Eq a => Eq (Sum a) Source | Since: base-2.1 |
Ord a => Ord (Sum a) Source | Since: base-2.1 |
Defined in Data.Semigroup.Internal |
|
type Rep1 Sum Source | Since: base-4.7.0.0 |
Defined in Data.Semigroup.Internal |
|
type Rep (Sum a) Source | Since: base-4.7.0.0 |
Defined in Data.Semigroup.Internal |
Monoid under multiplication.
>>> getProduct (Product 3 <> Product 4 <> mempty)
12
Constructors
Product | |
Fields
|
Instances
MonadFix Product Source | Since: base-4.8.0.0 |
Defined in Control.Monad.Fix |
|
MonadZip Product Source | Since: base-4.8.0.0 |
Foldable Product Source | Since: base-4.8.0.0 |
Defined in Data.Foldable Methodsfold :: Monoid m => Product m -> m Source foldMap :: Monoid m => (a -> m) -> Product a -> m Source foldMap' :: Monoid m => (a -> m) -> Product a -> m Source foldr :: (a -> b -> b) -> b -> Product a -> b Source foldr' :: (a -> b -> b) -> b -> Product a -> b Source foldl :: (b -> a -> b) -> b -> Product a -> b Source foldl' :: (b -> a -> b) -> b -> Product a -> b Source foldr1 :: (a -> a -> a) -> Product a -> a Source foldl1 :: (a -> a -> a) -> Product a -> a Source toList :: Product a -> [a] Source null :: Product a -> Bool Source length :: Product a -> Int Source elem :: Eq a => a -> Product a -> Bool Source maximum :: Ord a => Product a -> a Source minimum :: Ord a => Product a -> a Source |
|
Traversable Product Source | Since: base-4.8.0.0 |
Defined in Data.Traversable |
|
Applicative Product Source | Since: base-4.8.0.0 |
Defined in Data.Semigroup.Internal |
|
Functor Product Source | Since: base-4.8.0.0 |
Monad Product Source | Since: base-4.8.0.0 |
Generic1 Product Source | |
Data a => Data (Product a) Source | Since: base-4.8.0.0 |
Defined in Data.Data Methodsgfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Product a -> c (Product a) Source gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Product a) Source toConstr :: Product a -> Constr Source dataTypeOf :: Product a -> DataType Source dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Product a)) Source dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Product a)) Source gmapT :: (forall b. Data b => b -> b) -> Product a -> Product a Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Product a -> r Source gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Product a -> r Source gmapQ :: (forall d. Data d => d -> u) -> Product a -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> Product a -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> Product a -> m (Product a) Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Product a -> m (Product a) Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Product a -> m (Product a) Source |
|
Num a => Monoid (Product a) Source | Since: base-2.1 |
Num a => Semigroup (Product a) Source | Since: base-4.9.0.0 |
Bounded a => Bounded (Product a) Source | Since: base-2.1 |
Generic (Product a) Source | |
Num a => Num (Product a) Source | Since: base-4.7.0.0 |
Defined in Data.Semigroup.Internal Methods(+) :: Product a -> Product a -> Product a Source (-) :: Product a -> Product a -> Product a Source (*) :: Product a -> Product a -> Product a Source negate :: Product a -> Product a Source abs :: Product a -> Product a Source signum :: Product a -> Product a Source fromInteger :: Integer -> Product a Source |
|
Read a => Read (Product a) Source | Since: base-2.1 |
Show a => Show (Product a) Source | Since: base-2.1 |
Eq a => Eq (Product a) Source | Since: base-2.1 |
Ord a => Ord (Product a) Source | Since: base-2.1 |
Defined in Data.Semigroup.Internal |
|
type Rep1 Product Source | Since: base-4.7.0.0 |
Defined in Data.Semigroup.Internal |
|
type Rep (Product a) Source | Since: base-4.7.0.0 |
Defined in Data.Semigroup.Internal |
Difference lists of a semigroup
diff :: Semigroup m => m -> Endo m Source
This lets you use a difference list of a Semigroup
as a Monoid
.
Example:
>>> let hello = diff "Hello, "
>>> appEndo hello "World!"
"Hello, World!"
>>> appEndo (hello <> mempty) "World!"
"Hello, World!"
>>> appEndo (mempty <> hello) "World!"
"Hello, World!"
>>> let world = diff "World"
>>> let excl = diff "!"
>>> appEndo (hello <> (world <> excl)) mempty
"Hello, World!"
>>> appEndo ((hello <> world) <> excl) mempty
"Hello, World!"
cycle1 :: Semigroup m => m -> m Source
A generalization of cycle
to an arbitrary Semigroup
. May fail to terminate for some values in some semigroups.
ArgMin, ArgMax
Arg
isn't itself a Semigroup
in its own right, but it can be placed inside Min
and Max
to compute an arg min or arg max.
>>> minimum [ Arg (x * x) x | x <- [-10 .. 10] ]
Arg 0 0
Constructors
Instances
Bifoldable Arg Source | Since: base-4.10.0.0 |
Bifunctor Arg Source | Since: base-4.9.0.0 |
Bitraversable Arg Source | Since: base-4.10.0.0 |
Defined in Data.Semigroup Methodsbitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> Arg a b -> f (Arg c d) Source |
|
Generic1 (Arg a :: Type -> Type) Source | |
Foldable (Arg a) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodsfold :: Monoid m => Arg a m -> m Source foldMap :: Monoid m => (a0 -> m) -> Arg a a0 -> m Source foldMap' :: Monoid m => (a0 -> m) -> Arg a a0 -> m Source foldr :: (a0 -> b -> b) -> b -> Arg a a0 -> b Source foldr' :: (a0 -> b -> b) -> b -> Arg a a0 -> b Source foldl :: (b -> a0 -> b) -> b -> Arg a a0 -> b Source foldl' :: (b -> a0 -> b) -> b -> Arg a a0 -> b Source foldr1 :: (a0 -> a0 -> a0) -> Arg a a0 -> a0 Source foldl1 :: (a0 -> a0 -> a0) -> Arg a a0 -> a0 Source toList :: Arg a a0 -> [a0] Source null :: Arg a a0 -> Bool Source length :: Arg a a0 -> Int Source elem :: Eq a0 => a0 -> Arg a a0 -> Bool Source maximum :: Ord a0 => Arg a a0 -> a0 Source minimum :: Ord a0 => Arg a a0 -> a0 Source |
|
Traversable (Arg a) Source | Since: base-4.9.0.0 |
Functor (Arg a) Source | Since: base-4.9.0.0 |
(Data a, Data b) => Data (Arg a b) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup Methodsgfoldl :: (forall d b0. Data d => c (d -> b0) -> d -> c b0) -> (forall g. g -> c g) -> Arg a b -> c (Arg a b) Source gunfold :: (forall b0 r. Data b0 => c (b0 -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Arg a b) Source toConstr :: Arg a b -> Constr Source dataTypeOf :: Arg a b -> DataType Source dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Arg a b)) Source dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Arg a b)) Source gmapT :: (forall b0. Data b0 => b0 -> b0) -> Arg a b -> Arg a b Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Arg a b -> r Source gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Arg a b -> r Source gmapQ :: (forall d. Data d => d -> u) -> Arg a b -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> Arg a b -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> Arg a b -> m (Arg a b) Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Arg a b -> m (Arg a b) Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Arg a b -> m (Arg a b) Source |
|
Generic (Arg a b) Source | |
(Read a, Read b) => Read (Arg a b) Source | Since: base-4.9.0.0 |
(Show a, Show b) => Show (Arg a b) Source | Since: base-4.9.0.0 |
Eq a => Eq (Arg a b) Source | Since: base-4.9.0.0 |
Ord a => Ord (Arg a b) Source | Since: base-4.9.0.0 |
type Rep1 (Arg a :: Type -> Type) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup
type Rep1 (Arg a :: Type -> Type) = D1 ('MetaData "Arg" "Data.Semigroup" "base" 'False) (C1 ('MetaCons "Arg" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a) :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1))
|
|
type Rep (Arg a b) Source | Since: base-4.9.0.0 |
Defined in Data.Semigroup
type Rep (Arg a b) = D1 ('MetaData "Arg" "Data.Semigroup" "base" 'False) (C1 ('MetaCons "Arg" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a) :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 b)))
|
type ArgMin a b = Min (Arg a b) Source
>>> Min (Arg 0 ()) <> Min (Arg 1 ())
Min {getMin = Arg 0 ()}
type ArgMax a b = Max (Arg a b) Source
>>> Max (Arg 0 ()) <> Max (Arg 1 ())
Max {getMax = Arg 1 ()}
© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/9.4.2/docs/libraries/base-4.17.0.0/Data-Semigroup.html