newtype-generics-0.5/0000755000000000000000000000000013001473413013030 5ustar0000000000000000newtype-generics-0.5/LICENSE0000644000000000000000000000277313001473413014046 0ustar0000000000000000Copyright (c)2011, Darius Jahandarie 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 Darius Jahandarie 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. newtype-generics-0.5/newtype-generics.cabal0000644000000000000000000000272413001473413017311 0ustar0000000000000000Name: newtype-generics Version: 0.5 Synopsis: A typeclass and set of functions for working with newtypes, with generics support. Description: Per Conor McBride, the Newtype typeclass represents the packing and unpacking of a newtype, and allows you to operatate under that newtype with functions such as ala. Generics support was added in version 0.4, making this package a full replacement for the original newtype package, and a better alternative to newtype-th. License: BSD3 License-file: LICENSE Author: Darius Jahandarie, Conor McBride, João Cristóvão Maintainer: João Cristóvão -- Copyright: Category: Control Build-type: Simple -- Extra-source-files: Cabal-version: >=1.10 Library Exposed-modules: Control.Newtype Build-depends: base >= 4.6 && < 4.10 -- Other-modules: -- Build-tools: Ghc-options: -Wall default-language: Haskell2010 source-repository head type: git location: https://github.com/jcristovao/newtype-generics test-suite test type: exitcode-stdio-1.0 main-is: main.hs hs-source-dirs: test,. build-depends: base , hspec >= 2.1 && < 2.4 , HUnit >= 1.2.5.2 && < 1.6 default-language: Haskell2010 newtype-generics-0.5/Setup.hs0000644000000000000000000000005613001473413014465 0ustar0000000000000000import Distribution.Simple main = defaultMain newtype-generics-0.5/test/0000755000000000000000000000000013001473413014007 5ustar0000000000000000newtype-generics-0.5/test/main.hs0000644000000000000000000000005513001473413015267 0ustar0000000000000000{-# OPTIONS_GHC -F -pgmF hspec-discover #-} newtype-generics-0.5/Control/0000755000000000000000000000000013001473413014450 5ustar0000000000000000newtype-generics-0.5/Control/Newtype.hs0000644000000000000000000001665613001473413016455 0ustar0000000000000000{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances, TypeFamilies #-} {-# LANGUAGE DeriveGeneric #-} {-# LANGUAGE DefaultSignatures #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE StandaloneDeriving #-} {-# LANGUAGE UndecidableInstances #-} {- | The 'Newtype' typeclass and related functions: 'op', 'ala', 'ala'', 'under'. Primarly pulled from Conor McBride's Epigram work. Some examples: @ala Sum foldMap [1,2,3,4] -- foldMaps the list ala the Sum newtype. This results in 10.@ @ala Product foldMap [1,2,3,4] -- foldMaps the list ala the Product newtype. This results in 24.@ @ala Endo foldMap [(+1), (+2), (subtract 1), (*2)] 3 -- foldMaps the list ala the Endo newtype. This results in 8.@ NB: 'Data.Foldable.foldMap' is a generalized @mconcatMap@ which is a generalized @concatMap@. This package includes 'Newtype' instances for all the (non-GHC\/foreign) newtypes in base (as seen in the examples). However, there are neat things you can do with this with /any/ newtype and you should definitely define your own 'Newtype' instances for the power of this library. For example, see @ala Cont traverse@, with the proper 'Newtype' instance for Cont. You can easily define new instances for your newtypes with the help of GHC.Generics > {-# LANGUAGE DeriveGeneric #-} > import GHC.Generics > > (...) > newtype Example = Example Int > deriving (Generic) > > instance Newtype Example > This avoids the use of Template Haskell (TH) to get new instances. -} module Control.Newtype ( Newtype(..) , op , ala , ala' , under , over , underF , overF ) where import Data.Monoid import Control.Applicative import Control.Arrow import GHC.Generics {-import Generics.Deriving-} -- | Given a newtype @n@, we will always have the same unwrapped type @o@, -- meaning we can represent this with a fundep @n -> o@. -- -- Any instance of this class just needs to let @pack@ equal to the newtype's -- constructor, and let @unpack@ destruct the newtype with pattern matching. {-class Newtype n o | n -> o where-} {-pack :: o -> n-} {-unpack :: n -> o-} -- Generic Newtype class GNewtype n where type GO n :: * gpack :: GO n -> n p gunpack :: n p -> GO n -- We only need one instance, if these generic functions are only to work for -- newtypes, as these have a fixed form. For example, for a newtype X = Y, -- Rep X = D1 ... (C1 ... (S1 ... (K1 ... Y))) instance GNewtype (D1 d (C1 c (S1 s (K1 i a)))) where type GO (D1 d (C1 c (S1 s (K1 i a)))) = a gpack x = M1 (M1 (M1 (K1 x))) gunpack (M1 (M1 (M1 (K1 x)))) = x -- Original Newtype class, extended with generic defaults (trivial) and deprived -- of the second type argument (less trivial, as it involves a type family with -- a default, plus an equality constraint for the related type family in -- GNewtype). We do get rid of MultiParamTypeClasses and FunctionalDependencies, -- though. -- | As long as the type @n@ is an instance of Generic, you can create an instance -- with just @instance Newtype n@ class Newtype n where type O n :: * type O n = GO (Rep n) pack :: O n -> n default pack :: (Generic n, GNewtype (Rep n), O n ~ GO (Rep n)) => O n -> n pack = to . gpack unpack :: n -> O n default unpack :: (Generic n, GNewtype (Rep n), O n ~ GO (Rep n)) => n -> O n unpack = gunpack . from -- | -- This function serves two purposes: -- -- 1. Giving you the unpack of a newtype without you needing to remember the name. -- -- 2. Showing that the first parameter is /completely ignored/ on the value level, -- meaning the only reason you pass in the constructor is to provide type -- information. Typeclasses sure are neat. op :: (Newtype n,o ~ O n ) => (o -> n) -> n -> o op _ = unpack -- | The workhorse of the package. Given a pack and a \"higher order function\", -- it handles the packing and unpacking, and just sends you back a regular old -- function, with the type varying based on the hof you passed. -- -- The reason for the signature of the hof is due to 'ala' not caring about structure. -- To illustrate why this is important, another function in this package is 'under'. -- It is not extremely useful; @under2@ might be more useful (with e.g., @mappend@), -- but then we already digging the trench of -- \"What about @under3@? @under4@?\". -- The solution utilized here is to just hand off the \"packer\" to the hof. -- That way your structure can be imposed in the hof, -- whatever you may want it to be (e.g., List, Traversable). ala :: (Newtype n, Newtype n', o' ~ O n', o ~ O n) => (o -> n) -> ((o -> n) -> b -> n') -> (b -> o') ala pa hof = ala' pa hof id -- | This is the original function seen in Conor McBride's work. -- The way it differs from the 'ala' function in this package, -- is that it provides an extra hook into the \"packer\" passed to the hof. -- However, this normally ends up being @id@, so 'ala' wraps this function and -- passes @id@ as the final parameter by default. -- If you want the convenience of being able to hook right into the hof, -- you may use this function. ala' :: (Newtype n, Newtype n', o' ~ O n', o ~ O n) => (o -> n) -> ((a -> n) -> b -> n') -> (a -> o) -> (b -> o') ala' _ hof f = unpack . hof (pack . f) -- | A very simple operation involving running the function \'under\' the newtype. -- Suffers from the problems mentioned in the 'ala' function's documentation. under :: (Newtype n, Newtype n', o' ~ O n', o ~ O n) => (o -> n) -> (n -> n') -> (o -> o') under _ f = unpack . f . pack -- | The opposite of 'under'. I.e., take a function which works on the -- underlying types, and switch it to a function that works on the newtypes. over :: (Newtype n, Newtype n', o' ~ O n', o ~ O n) => (o -> n) -> (o -> o') -> (n -> n') over _ f = pack . f . unpack -- | 'under' lifted into a Functor. underF :: (Newtype n, Newtype n', o' ~ O n', o ~ O n, Functor f, Functor g) => (o -> n) -> (f n -> g n') -> (f o -> g o') underF _ f = fmap unpack . f . fmap pack -- | 'over' lifted into a Functor. overF :: (Newtype n, Newtype n', o' ~ O n', o ~ O n, Functor f, Functor g) => (o -> n) -> (f o -> g o') -> (f n -> g n') overF _ f = fmap pack . f . fmap unpack instance Newtype All where type O All = Bool pack = All unpack (All x) = x instance Newtype Any where type O Any = Bool pack = Any unpack (Any x) = x instance Newtype (Sum a) where type O (Sum a) = a pack = Sum unpack (Sum a) = a instance Newtype (Product a) where type O (Product a) = a pack = Product unpack (Product a) = a instance Newtype (First a) where type O (First a) = Maybe a pack = First unpack (First a) = a instance Newtype (Last a) where type O (Last a) = Maybe a pack = Last unpack (Last a) = a instance Newtype (Endo a) where type O (Endo a) = (a -> a) pack = Endo unpack (Endo a) = a instance Newtype (ZipList a) where type O (ZipList a) = [a] pack = ZipList unpack (ZipList a) = a instance Newtype (Const a x) where type O (Const a x) = a pack = Const unpack (Const a) = a instance Newtype (Kleisli m a b) where type O (Kleisli m a b) = a -> m b pack = Kleisli unpack (Kleisli a) = a instance Newtype (WrappedMonad m a) where type O (WrappedMonad m a) = m a pack = WrapMonad unpack (WrapMonad a) = a instance Newtype (WrappedArrow a b c) where type O (WrappedArrow a b c) = a b c pack = WrapArrow unpack (WrapArrow a) = a instance Newtype (ArrowMonad a b) where type O (ArrowMonad a b) = a () b pack = ArrowMonad unpack (ArrowMonad a) = a