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Data.Monoid |
Portability | non-portable (requires extended type classes)
Stability | experimental
Maintainer | libraries@haskell.org
Description
Declaration of the Monoid class, and instances for list and functions. 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
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 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 (a -> a)
Ord a => Monoid (IntMap a)
Ord a => Monoid (Set a)
Monoid [a]
Ord k => Monoid (Map k v)
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