acme-cofunctor 0.1.0.0 → 0.1.1.0

raw patch · 4 files changed

+62/−3 lines, 4 filesPVP: major bump suggested

API removals or changes: PVP suggests a major version bump

API changes (from Hackage documentation)

Files

• CHANGELOG.md +8/−0
• README.md +17/−0
• acme-cofunctor.cabal +10/−3
• src/Data/Cofunctor/Cocoyoneda.hs +27/−0

@@ -0,0 +1,8 @@+CHANGELOG+=========++- 0.1.1.0 (2017-05-13)+    * Add `Data.Cofunctor.Cocoyoneda` module++- 0.1.0.0 (2014-11-28)+    * Initial release

@@ -0,0 +1,17 @@+acme-cofunctor+==============++A `Cofunctor` is a structure from category theory dual to `Functor`.++We all know that 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.

@@ -1,5 +1,5 @@ Name:          acme-cofunctor-Version:       0.1.0.0+Version:       0.1.1.0 Synopsis:      A Cofunctor is a structure from category theory dual to Functor License:       BSD3 License-file:  LICENSE@@ -37,11 +37,18 @@   ubiquitous Haskell types (e.g. @[]@, 'Maybe', @((->) a)@ turn out to have a   'Cofunctor' instance. +Extra-source-files:+  README.md+  CHANGELOG.md+ Library-  Exposed-modules:  Data.Cofunctor-  default-language: Haskell98+  Default-language: Haskell98   Ghc-options:      -Wall   Hs-source-dirs:   src++  Exposed-modules:+    Data.Cofunctor,+    Data.Cofunctor.Cocoyoneda    Build-depends:     base >= 4 && < 5

@@ -0,0 +1,27 @@+{-# LANGUAGE GADTs #-}+{-# LANGUAGE RankNTypes #-}++-- | 'Cocoyoneda' gives a cofree cofunctor for any type constructor.+module Data.Cofunctor.Cocoyoneda+    ( Cocoyoneda(..)+    , liftCocoyoneda+    , lowerCocoyoneda+    , hoistCocoyoneda+    ) where++import Data.Cofunctor (Cofunctor(..))++data Cocoyoneda f a where+    Cocoyoneda :: (a -> b) -> f a -> Cocoyoneda f b++instance Cofunctor (Cocoyoneda f) where+    cofmap f (Cocoyoneda g x) = Cocoyoneda (f . g) x++liftCocoyoneda :: f a -> Cocoyoneda f a+liftCocoyoneda = Cocoyoneda id++lowerCocoyoneda :: Cofunctor f => Cocoyoneda f a -> f a+lowerCocoyoneda (Cocoyoneda f x) = cofmap f x++hoistCocoyoneda :: (forall a. f a -> g a) -> Cocoyoneda f b -> Cocoyoneda g b+hoistCocoyoneda f (Cocoyoneda g x) = Cocoyoneda g (f x)