| Copyright | (C) 2011-2015 Edward Kmett |
|---|---|
| License | BSD-style (see the file LICENSE) |
| Maintainer | [email protected] |
| Stability | provisional |
| Portability | portable |
| Safe Haskell | Trustworthy |
| Language | Haskell2010 |
In mathematics, a semigroup is an algebraic structure consisting of a set together with an associative binary operation. A semigroup generalizes a monoid in that there might not exist an identity element. It also (originally) generalized a group (a monoid with all inverses) to a type where every element did not have to have an inverse, thus the name semigroup.
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: 4.9.0.0
class Semigroup a where Source
The class of semigroups (types with an associative binary operation).
Since: 4.9.0.0
(<>) :: a -> a -> a infixr 6 Source
An associative operation.
(a<>b)<>c = a<>(b<>c)
If a is also a Monoid we further require
(<>) =mappend
(<>) :: Monoid a => a -> a -> a infixr 6 Source
An associative operation.
(a<>b)<>c = a<>(b<>c)
If a is also a Monoid we further require
(<>) =mappend
sconcat :: NonEmpty a -> a Source
Reduce a non-empty list with <>
The default definition should be sufficient, but this can be overridden for efficiency.
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 O(1) by picking stimes = stimesIdempotent or stimes = stimesIdempotentMonoid respectively.
| Semigroup Ordering | Since: 4.9.0.0 |
| Semigroup () | Since: 4.9.0.0 |
| Semigroup Any | Since: 4.9.0.0 |
| Semigroup All | Since: 4.9.0.0 |
| Semigroup Lifetime | Since: 4.10.0.0 |
| Semigroup Event | Since: 4.10.0.0 |
| Semigroup Void | Since: 4.9.0.0 |
| Semigroup [a] | Since: 4.9.0.0 |
| Semigroup a => Semigroup (Maybe a) | Since: 4.9.0.0 |
| Semigroup a => Semigroup (IO a) | Since: 4.10.0.0 |
| Semigroup (Last a) | Since: 4.9.0.0 |
| Semigroup (First a) | Since: 4.9.0.0 |
| Num a => Semigroup (Product a) | Since: 4.9.0.0 |
| Num a => Semigroup (Sum a) | Since: 4.9.0.0 |
| Semigroup (Endo a) | Since: 4.9.0.0 |
| Semigroup a => Semigroup (Dual a) | Since: 4.9.0.0 |
| Semigroup a => Semigroup (Identity a) | Since: 4.9.0.0 |
| Semigroup (NonEmpty a) | Since: 4.9.0.0 |
| Semigroup a => Semigroup (Option a) | Since: 4.9.0.0 |
| Monoid m => Semigroup (WrappedMonoid m) | Since: 4.9.0.0 |
| Semigroup (Last a) | Since: 4.9.0.0 |
| Semigroup (First a) | Since: 4.9.0.0 |
| Ord a => Semigroup (Max a) | Since: 4.9.0.0 |
| Ord a => Semigroup (Min a) | Since: 4.9.0.0 |
| Semigroup b => Semigroup (a -> b) | Since: 4.9.0.0 |
| Semigroup (Either a b) | Since: 4.9.0.0 |
| (Semigroup a, Semigroup b) => Semigroup (a, b) | Since: 4.9.0.0 |
| Semigroup (Proxy k s) | Since: 4.9.0.0 |
| (Semigroup a, Semigroup b, Semigroup c) => Semigroup (a, b, c) | Since: 4.9.0.0 |
| Alternative f => Semigroup (Alt * f a) | Since: 4.9.0.0 |
| Semigroup a => Semigroup (Const k a b) | Since: 4.9.0.0 |
| (Semigroup a, Semigroup b, Semigroup c, Semigroup d) => Semigroup (a, b, c, d) | Since: 4.9.0.0 |
| (Semigroup a, Semigroup b, Semigroup c, Semigroup d, Semigroup e) => Semigroup (a, b, c, d, e) | Since: 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 O(1) rather than 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 O(1) rather than 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
Implemented using stimes and mempty.
This is a suitable definition for an mtimes member of Monoid.
| Monad Min | Since: 4.9.0.0 |
| Functor Min | Since: 4.9.0.0 |
| MonadFix Min | Since: 4.9.0.0 |
| Applicative Min | Since: 4.9.0.0 |
| Foldable Min | Since: 4.9.0.0 |
| Traversable Min | Since: 4.9.0.0 |
| Bounded a => Bounded (Min a) | |
| Enum a => Enum (Min a) | Since: 4.9.0.0 |
| Eq a => Eq (Min a) | |
| Data a => Data (Min a) | |
| Num a => Num (Min a) | Since: 4.9.0.0 |
| Ord a => Ord (Min a) | |
| Read a => Read (Min a) | |
| Show a => Show (Min a) | |
| Generic (Min a) | |
| Ord a => Semigroup (Min a) | Since: 4.9.0.0 |
| (Ord a, Bounded a) => Monoid (Min a) | Since: 4.9.0.0 |
| Generic1 * Min | |
| type Rep (Min a) | |
| type Rep1 * Min | |
| Monad Max | Since: 4.9.0.0 |
| Functor Max | Since: 4.9.0.0 |
| MonadFix Max | Since: 4.9.0.0 |
| Applicative Max | Since: 4.9.0.0 |
| Foldable Max | Since: 4.9.0.0 |
| Traversable Max | Since: 4.9.0.0 |
| Bounded a => Bounded (Max a) | |
| Enum a => Enum (Max a) | Since: 4.9.0.0 |
| Eq a => Eq (Max a) | |
| Data a => Data (Max a) | |
| Num a => Num (Max a) | Since: 4.9.0.0 |
| Ord a => Ord (Max a) | |
| Read a => Read (Max a) | |
| Show a => Show (Max a) | |
| Generic (Max a) | |
| Ord a => Semigroup (Max a) | Since: 4.9.0.0 |
| (Ord a, Bounded a) => Monoid (Max a) | Since: 4.9.0.0 |
| Generic1 * Max | |
| type Rep (Max a) | |
| type Rep1 * Max | |
Use Option (First a) to get the behavior of First from Data.Monoid.
| Monad First | Since: 4.9.0.0 |
| Functor First | Since: 4.9.0.0 |
| MonadFix First | Since: 4.9.0.0 |
| Applicative First | Since: 4.9.0.0 |
| Foldable First | Since: 4.9.0.0 |
| Traversable First | Since: 4.9.0.0 |
| Bounded a => Bounded (First a) | |
| Enum a => Enum (First a) | Since: 4.9.0.0 |
| Eq a => Eq (First a) | |
| Data a => Data (First a) | |
| Ord a => Ord (First a) | |
| Read a => Read (First a) | |
| Show a => Show (First a) | |
| Generic (First a) | |
| Semigroup (First a) | Since: 4.9.0.0 |
| Generic1 * First | |
| type Rep (First a) | |
| type Rep1 * First | |
Use Option (Last a) to get the behavior of Last from Data.Monoid
| Monad Last | Since: 4.9.0.0 |
| Functor Last | Since: 4.9.0.0 |
| MonadFix Last | Since: 4.9.0.0 |
| Applicative Last | Since: 4.9.0.0 |
| Foldable Last | Since: 4.9.0.0 |
| Traversable Last | Since: 4.9.0.0 |
| Bounded a => Bounded (Last a) | |
| Enum a => Enum (Last a) | Since: 4.9.0.0 |
| Eq a => Eq (Last a) | |
| Data a => Data (Last a) | |
| Ord a => Ord (Last a) | |
| Read a => Read (Last a) | |
| Show a => Show (Last a) | |
| Generic (Last a) | |
| Semigroup (Last a) | Since: 4.9.0.0 |
| Generic1 * Last | |
| type Rep (Last a) | |
| type Rep1 * Last | |
newtype WrappedMonoid m Source
Provide a Semigroup for an arbitrary Monoid.
| WrapMonoid | |
Fields
| |
| Bounded m => Bounded (WrappedMonoid m) | |
| Enum a => Enum (WrappedMonoid a) | Since: 4.9.0.0 |
| Eq m => Eq (WrappedMonoid m) | |
| Data m => Data (WrappedMonoid m) | |
| Ord m => Ord (WrappedMonoid m) | |
| Read m => Read (WrappedMonoid m) | |
| Show m => Show (WrappedMonoid m) | |
| Generic (WrappedMonoid m) | |
| Monoid m => Semigroup (WrappedMonoid m) | Since: 4.9.0.0 |
| Monoid m => Monoid (WrappedMonoid m) | Since: 4.9.0.0 |
| Generic1 * WrappedMonoid | |
| type Rep (WrappedMonoid m) | |
| type Rep1 * WrappedMonoid | |
The class of monoids (types with an associative binary operation that has an identity). Instances should satisfy the following laws:
mappend mempty x = x
mappend x mempty = x
mappend x (mappend y z) = mappend (mappend x y) z
mconcat = foldr mappend memptyThe 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.
Identity of mappend
An associative operation
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.
| Monoid Ordering | Since: 2.1 |
| Monoid () | Since: 2.1 |
| Monoid Any | Since: 2.1 |
| Monoid All | Since: 2.1 |
| Monoid Lifetime |
Since: 4.8.0.0 |
| Monoid Event | Since: 4.3.1.0 |
| Monoid [a] | Since: 2.1 |
| Monoid a => Monoid (Maybe a) |
Lift a semigroup into Since: 2.1 |
| Monoid a => Monoid (IO a) | Since: 4.9.0.0 |
| Monoid (Last a) | Since: 2.1 |
| Monoid (First a) | Since: 2.1 |
| Num a => Monoid (Product a) | Since: 2.1 |
| Num a => Monoid (Sum a) | Since: 2.1 |
| Monoid (Endo a) | Since: 2.1 |
| Monoid a => Monoid (Dual a) | Since: 2.1 |
| Monoid a => Monoid (Identity a) | |
| Semigroup a => Monoid (Option a) | Since: 4.9.0.0 |
| Monoid m => Monoid (WrappedMonoid m) | Since: 4.9.0.0 |
| (Ord a, Bounded a) => Monoid (Max a) | Since: 4.9.0.0 |
| (Ord a, Bounded a) => Monoid (Min a) | Since: 4.9.0.0 |
| Monoid b => Monoid (a -> b) | Since: 2.1 |
| (Monoid a, Monoid b) => Monoid (a, b) | Since: 2.1 |
| Monoid (Proxy k s) | Since: 4.7.0.0 |
| (Monoid a, Monoid b, Monoid c) => Monoid (a, b, c) | Since: 2.1 |
| Alternative f => Monoid (Alt * f a) | Since: 4.8.0.0 |
| Monoid a => Monoid (Const k a b) | |
| (Monoid a, Monoid b, Monoid c, Monoid d) => Monoid (a, b, c, d) | Since: 2.1 |
| (Monoid a, Monoid b, Monoid c, Monoid d, Monoid e) => Monoid (a, b, c, d, e) | Since: 2.1 |
The dual of a Monoid, obtained by swapping the arguments of mappend.
| Monad Dual | Since: 4.8.0.0 |
| Functor Dual | Since: 4.8.0.0 |
| MonadFix Dual | Since: 4.8.0.0 |
| Applicative Dual | Since: 4.8.0.0 |
| Foldable Dual | Since: 4.8.0.0 |
| Traversable Dual | Since: 4.8.0.0 |
| MonadZip Dual | Since: 4.8.0.0 |
| Bounded a => Bounded (Dual a) | |
| Eq a => Eq (Dual a) | |
| Data a => Data (Dual a) | Since: 4.8.0.0 |
| Ord a => Ord (Dual a) | |
| Read a => Read (Dual a) | |
| Show a => Show (Dual a) | |
| Generic (Dual a) | |
| Semigroup a => Semigroup (Dual a) | Since: 4.9.0.0 |
| Monoid a => Monoid (Dual a) | Since: 2.1 |
| Generic1 * Dual | |
| type Rep (Dual a) | |
| type Rep1 * Dual | |
The monoid of endomorphisms under composition.
Boolean monoid under conjunction (&&).
Boolean monoid under disjunction (||).
Monoid under addition.
| Monad Sum | Since: 4.8.0.0 |
| Functor Sum | Since: 4.8.0.0 |
| MonadFix Sum | Since: 4.8.0.0 |
| Applicative Sum | Since: 4.8.0.0 |
| Foldable Sum | Since: 4.8.0.0 |
| Traversable Sum | Since: 4.8.0.0 |
| MonadZip Sum | Since: 4.8.0.0 |
| Bounded a => Bounded (Sum a) | |
| Eq a => Eq (Sum a) | |
| Data a => Data (Sum a) | Since: 4.8.0.0 |
| Num a => Num (Sum a) | |
| Ord a => Ord (Sum a) | |
| Read a => Read (Sum a) | |
| Show a => Show (Sum a) | |
| Generic (Sum a) | |
| Num a => Semigroup (Sum a) | Since: 4.9.0.0 |
| Num a => Monoid (Sum a) | Since: 2.1 |
| Generic1 * Sum | |
| type Rep (Sum a) | |
| type Rep1 * Sum | |
Monoid under multiplication.
| Product | |
Fields
| |
| Monad Product | Since: 4.8.0.0 |
| Functor Product | Since: 4.8.0.0 |
| MonadFix Product | Since: 4.8.0.0 |
| Applicative Product | Since: 4.8.0.0 |
| Foldable Product | Since: 4.8.0.0 |
| Traversable Product | Since: 4.8.0.0 |
| MonadZip Product | Since: 4.8.0.0 |
| Bounded a => Bounded (Product a) | |
| Eq a => Eq (Product a) | |
| Data a => Data (Product a) | Since: 4.8.0.0 |
| Num a => Num (Product a) | |
| Ord a => Ord (Product a) | |
| Read a => Read (Product a) | |
| Show a => Show (Product a) | |
| Generic (Product a) | |
| Num a => Semigroup (Product a) | Since: 4.9.0.0 |
| Num a => Monoid (Product a) | Since: 2.1 |
| Generic1 * Product | |
| type Rep (Product a) | |
| type Rep1 * Product | |
Option is effectively Maybe with a better instance of Monoid, built off of an underlying Semigroup instead of an underlying Monoid.
Ideally, this type would not exist at all and we would just fix the Monoid instance of Maybe
| Monad Option | Since: 4.9.0.0 |
| Functor Option | Since: 4.9.0.0 |
| MonadFix Option | Since: 4.9.0.0 |
| Applicative Option | Since: 4.9.0.0 |
| Foldable Option | Since: 4.9.0.0 |
| Traversable Option | Since: 4.9.0.0 |
| MonadPlus Option | Since: 4.9.0.0 |
| Alternative Option | Since: 4.9.0.0 |
| Eq a => Eq (Option a) | |
| Data a => Data (Option a) | |
| Ord a => Ord (Option a) | |
| Read a => Read (Option a) | |
| Show a => Show (Option a) | |
| Generic (Option a) | |
| Semigroup a => Semigroup (Option a) | Since: 4.9.0.0 |
| Semigroup a => Monoid (Option a) | Since: 4.9.0.0 |
| Generic1 * Option | |
| type Rep (Option a) | |
| type Rep1 * Option | |
option :: b -> (a -> b) -> Option a -> b Source
Fold an Option case-wise, just like maybe.
diff :: Semigroup m => m -> Endo m Source
This lets you use a difference list of a Semigroup as a Monoid.
cycle1 :: Semigroup m => m -> m Source
A generalization of cycle to an arbitrary Semigroup. May fail to terminate for some values in some semigroups.
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.
| Arg a b |
| Bifunctor Arg | Since: 4.9.0.0 |
| Bifoldable Arg | Since: 4.10.0.0 |
| Bitraversable Arg | Since: 4.10.0.0 |
| Functor (Arg a) | Since: 4.9.0.0 |
| Foldable (Arg a) | Since: 4.9.0.0 |
| Traversable (Arg a) | Since: 4.9.0.0 |
| Generic1 * (Arg a) | |
| Eq a => Eq (Arg a b) | Since: 4.9.0.0 |
| (Data b, Data a) => Data (Arg a b) | |
| Ord a => Ord (Arg a b) | Since: 4.9.0.0 |
| (Read b, Read a) => Read (Arg a b) | |
| (Show b, Show a) => Show (Arg a b) | |
| Generic (Arg a b) | |
| type Rep1 * (Arg a) | |
| type Rep (Arg a b) | |
© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/8.2.1/docs/html/libraries/base-4.10.0.0/Data-Semigroup.html