diff --git a/Data/Semiring.hs b/Data/Semiring.hs new file mode 100644 --- /dev/null +++ b/Data/Semiring.hs @@ -0,0 +1,50 @@ +-- | +-- Module : Data.Semiring +-- Copyright : Thomas Wilke, Frank Huch, Sebastian Fischer, Peter Harpending +-- License : BSD3 +-- Maintainer : Peter Harpending +-- +-- This library provides a type class for semirings. +-- + +module Data.Semiring where + +-- | +-- A semiring is an additive commutative monoid with identity 'zero': +-- +-- > a .+. b == b .+. a +-- > zero .+. a == a +-- > (a .+. b) .+. c == a .+. (b .+. c) +-- +-- A semiring is a multiplicative monoid with identity 'one': +-- +-- > one .*. a == a +-- > a .*. one == a +-- > (a .*. b) .*. c == a .*. (b .*. c) +-- +-- Multiplication distributes over addition: +-- +-- > a .*. (b .+. c) == (a .*. b) .+. (a .*. c) +-- > (a .+. b) .*. c == (a .*. c) .+. (b .*. c) +-- +-- 'zero' annihilates a semiring with respect to multiplication: +-- +-- > zero .*. a == zero +-- > a .*. zero == zero +-- +-- All laws should hold with respect to the required `Eq` instance. +-- +-- For example, the Booleans form a semiring. +-- +-- * @False@ is an identity of disjunction which is commutative and +-- associative, +-- +-- * @True@ is an identity of conjunction which is associative, +-- +-- * conjunction distributes over disjunction, and +-- +-- * @False@ annihilates the Booleans with respect to conjunction. +-- +class (Eq s) => Semiring s where + zero, one :: s + (.+.), (.*.) :: s -> s -> s diff --git a/LICENSE b/LICENSE new file mode 100644 --- /dev/null +++ b/LICENSE @@ -0,0 +1,30 @@ +Copyright (c) 2014, Thomas Wilke, Frank Huch, Sebastian Fischer, Peter Harpending + +All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions are met: + + * Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + + * Redistributions in binary form must reproduce the above + copyright notice, this list of conditions and the following + disclaimer in the documentation and/or other materials provided + with the distribution. + + * Neither the name of Thomas Wilke, Frank Huch, Sebastian Fischer, Peter Harpending nor the names of other + contributors may be used to endorse or promote products derived + from this software without specific prior written permission. + +THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. diff --git a/README.md b/README.md new file mode 100644 --- /dev/null +++ b/README.md @@ -0,0 +1,7 @@ +# Semiring + +This is a Haskell library for dealing with semirings. + +The source file comes from the apparently abandoned +[weighted-regexp](http://hackage.haskell.org/package/weighted-regexp-0.3.1.2) +package on Hackage. diff --git a/Setup.hs b/Setup.hs new file mode 100644 --- /dev/null +++ b/Setup.hs @@ -0,0 +1,2 @@ +import Distribution.Simple +main = defaultMain diff --git a/semiring-simple.cabal b/semiring-simple.cabal new file mode 100644 --- /dev/null +++ b/semiring-simple.cabal @@ -0,0 +1,71 @@ +-- Initial semiring.cabal generated by cabal init. For further +-- documentation, see http://haskell.org/cabal/users-guide/ + +-- The name of the package. +name: semiring-simple + +-- The package version. See the Haskell package versioning policy (PVP) +-- for standards guiding when and how versions should be incremented. +-- http://www.haskell.org/haskellwiki/Package_versioning_policy +-- PVP summary: +-+------- breaking API changes +-- | | +----- non-breaking API additions +-- | | | +--- code changes with no API change +version: 0.1.0.0 + +-- A short (one-line) description of the package. +synopsis: A module for dealing with semirings. + +-- A longer description of the package. +description: Semirings are like normal rings, except you can't subtract. This library provides a type class for semirings. + +-- The license under which the package is released. +license: BSD3 + +-- The file containing the license text. +license-file: LICENSE + +-- The package author(s). +author: Thomas Wilke, Frank Huch, Sebastian Fischer, Peter Harpending + +-- An email address to which users can send suggestions, bug reports, and +-- patches. +maintainer: pharpend2@gmail.com + +-- A copyright notice. +-- copyright: 2014 + +category: Math + +build-type: Simple + +-- Extra files to be distributed with the package, such as examples or a +-- README. +extra-source-files: README.md + +-- Constraint on the version of Cabal needed to build this package. +cabal-version: >=1.10 + + +library + -- Modules exported by the library. + exposed-modules: Data.Semiring + + -- Modules included in this library but not exported. + -- other-modules: + + -- LANGUAGE extensions used by modules in this package. + -- other-extensions: + + -- Other library packages from which modules are imported. + build-depends: base >=4.6 && <4.7 + + -- Directories containing source files. + -- hs-source-dirs: + + -- Base language which the package is written in. + default-language: Haskell2010 + + +source-repository head + type: git + location: https://github.com/pharpend/semiring.git