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semigroups
==========
[](https://hackage.haskell.org/package/semigroups) [](https://github.com/ekmett/semigroups/actions?query=workflow%3AHaskell-CI)
Haskellers are usually familiar with monoids. A monoid has an appending operation `<>` or `mappend` and an identity element `mempty`. A Semigroup has an append `<>`, but does not require an `mempty` element. A Monoid can be made a Semigroup with just `instance Semigroup MyMonoid`
More formally, 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.
`Data.Semigroup` and `Data.List.NonEmpty` were added to `base` as of 4.9.0.0. This package now offers a backwards-compatible API and some tools for deriving semigroups with generics.
Contact Information
-------------------
Contributions and bug reports are welcome!
Please feel free to contact me through github or on the #haskell IRC channel on irc.freenode.net.
-Edward Kmett
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