acme-cofunctor (empty) → 0.1.0.0
raw patch · 4 files changed
+127/−0 lines, 4 filesdep +basesetup-changed
Dependencies added: base
Files
- LICENSE +30/−0
- Setup.hs +2/−0
- acme-cofunctor.cabal +51/−0
- src/Data/Cofunctor.hs +44/−0
+ LICENSE view
@@ -0,0 +1,30 @@+Copyright (c) 2014, Jasper Van der Jeugt <m@jaspervdj.be>++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 Jasper Van der Jeugt <m@jaspervdj.be> 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.
+ Setup.hs view
@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain
+ acme-cofunctor.cabal view
@@ -0,0 +1,51 @@+Name: acme-cofunctor+Version: 0.1.0.0+Synopsis: A Cofunctor is a structure from category theory dual to Functor+License: BSD3+License-file: LICENSE+Author: Jasper Van der Jeugt <m@jaspervdj.be>+Maintainer: Jasper Van der Jeugt <m@jaspervdj.be>+Copyright: 2014 Jasper Van der Jeugt+Category: Acme+Build-type: Simple+Cabal-version: >= 1.10+Homepage: https://github.com/jaspervdj/acme-cofunctor++Description:+ A 'Cofunctor' is a structure from category theory dual to 'Functor'.++ .++ A 'Functor' is defined by the operation 'fmap':++ .++ > fmap :: (a -> b) -> (f a -> f b)++ .++ This means that its dual must be defined by the following operation:++ .++ > cofmap :: (b -> a) -> (f b -> f a)++ .++ Since beginning his investigations, the author of this package has discovered+ that this pattern is /at least/ as commonly used as 'Functor'. In fact, many+ ubiquitous Haskell types (e.g. @[]@, 'Maybe', @((->) a)@ turn out to have a+ 'Cofunctor' instance.++Library+ Exposed-modules: Data.Cofunctor+ default-language: Haskell98+ Ghc-options: -Wall+ Hs-source-dirs: src++ Build-depends:+ base >= 4 && < 5++Source-repository head+ Type: git+ Location: https://github.com/jaspervdj/acme-cofunctor
+ src/Data/Cofunctor.hs view
@@ -0,0 +1,44 @@+-- | 'Cofunctor' is a structure from category theory dual to 'Functor'+--+-- A 'Functor' is defined by the operation 'fmap':+--+-- > fmap :: (a -> b) -> (f a -> f b)+--+-- This means that its dual must be defined by the following operation:+--+-- > cofmap :: (b -> a) -> (f b -> f a)+--+-- Since beginning his investigations, the author of this package has discovered+-- that this pattern is /at least/ as commonly used as 'Functor'. In fact, many+-- ubiquitous Haskell types (e.g. @[]@, 'Maybe', @((->) a)@ turn out to have a+-- 'Cofunctor' instance.+module Data.Cofunctor+ ( Cofunctor (..)+ ) where++import Control.Monad (liftM)++-- | 'Cofunctor' is a structure from category theory dual to 'Functor'+class Cofunctor f where+ cofmap :: (b -> a) -> f b -> f a++instance Cofunctor [] where+ cofmap _ [] = []+ cofmap f (x : xs) = f x : cofmap f xs++instance Cofunctor Maybe where+ cofmap _ Nothing = Nothing+ cofmap f (Just x) = Just (f x)++instance Cofunctor (Either e) where+ cofmap _ (Left e) = Left e+ cofmap f (Right x) = Right (f x)++instance Cofunctor ((->) a) where+ cofmap = (.)++instance Cofunctor ((,) a) where+ cofmap f (e, x) = (e, f x)++instance Cofunctor IO where+ cofmap = liftM