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 mempty
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 newtype
s 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