| Haskell Hierarchical Libraries (base package) | Source code | Contents | Index
Data.Monoid |
Portability | portable
Stability | experimental
Maintainer | libraries@haskell.org
Description
The Monoid class with various general-purpose instances. Inspired by the paper Functional Programming with Overloading and Higher-Order Polymorphism, Mark P Jones (http://www.cse.ogi.edu/~mpj/) Advanced School of Functional Programming, 1995.
Synopsis
class Monoid a where
mempty :: a
mappend :: a -> a -> a
mconcat :: [a] -> a
newtype Dual a = Dual {
getDual :: a
}
newtype Endo a = Endo {
appEndo :: (a -> a)
}
newtype All = All {
getAll :: Bool
}
newtype Any = Any {
getAny :: Bool
}
newtype Sum a = Sum {
getSum :: a
}
newtype Product a = Product {
getProduct :: a
}
Documentation
class Monoid a where
The monoid class. A minimal complete definition must supply `mempty` and `mappend`, and these should satisfy the monoid laws.
Methods
mempty :: a
Identity of `mappend`
mappend :: a -> a -> a
An associative operation
mconcat :: [a] -> a
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.
Instances
Monoid All
Monoid Any
Monoid ByteString
Monoid ByteString
Monoid IntSet
Monoid Ordering
Monoid ()
(Monoid a, Monoid b) => Monoid (a, b)
(Monoid a, Monoid b, Monoid c) => Monoid (a, b, c)
(Monoid a, Monoid b, Monoid c, Monoid d) => Monoid (a, b, c, d)
(Monoid a, Monoid b, Monoid c, Monoid d, Monoid e) => Monoid (a, b, c, d, e)
Monoid b => Monoid (a -> b)
Monoid a => Monoid (Dual a)
Monoid (Endo a)
Monoid (IntMap a)
Num a => Monoid (Product a)
Monoid (Seq a)
Ord a => Monoid (Set a)
Num a => Monoid (Sum a)
Monoid [a]
Ord k => Monoid (Map k v)
newtype Dual a
The dual of a monoid, obtained by swapping the arguments of `mappend`.
Constructors
Dual |
getDual :: a |
Instances
Monoid a => Monoid (Dual a)
newtype Endo a
The monoid of endomorphisms under composition.
Constructors
Endo |
appEndo :: (a -> a) |
Instances
Monoid (Endo a)
newtype All
Boolean monoid under conjunction.
Constructors
All |
getAll :: Bool |
Instances
Bounded All
Eq All
Monoid All
Ord All
Read All
Show All
newtype Any
Boolean monoid under disjunction.
Constructors
Any |
getAny :: Bool |
Instances
Bounded Any
Eq Any
Monoid Any
Ord Any
Read Any
Show Any
newtype Sum a
Monoid under addition.
Constructors
Sum |
getSum :: a |
Instances
Bounded a => Bounded (Sum a)
Eq a => Eq (Sum a)
Num a => Monoid (Sum a)
Ord a => Ord (Sum a)
Read a => Read (Sum a)
Show a => Show (Sum a)
newtype Product a
Monoid under multiplication.
Constructors
Product |
getProduct :: a |
Instances
Bounded a => Bounded (Product a)
Eq a => Eq (Product a)
Num a => Monoid (Product a)
Ord a => Ord (Product a)
Read a => Read (Product a)
Show a => Show (Product a)
Produced by Haddock version 0.8