https://github.com/sheaf/groups-generic

Derive Group instances using generics (Haskell library)
https://github.com/sheaf/groups-generic

Last synced: 8 months ago
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Derive Group instances using generics (Haskell library)

• Host: GitHub
• URL: https://github.com/sheaf/groups-generic
• Owner: sheaf
• Created: 2020-02-14T20:41:46.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2024-02-16T15:00:50.000Z (over 2 years ago)
• Last Synced: 2025-01-31T13:12:10.447Z (over 1 year ago)
• Language: Haskell
• Size: 6.84 KB
• Stars: 3
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: readme.md
  • Changelog: changelog.md

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README

          

# groups-generic 

Extends the [groups](https://hackage.haskell.org/package/groups) library with functionality for deriving `Group` instances using generics:

```haskell

{-# LANGUAGE DeriveGeneric #-}

{-# LANGUAGE DerivingVia   #-}

module Example where

-- base

import Data.Semigroup

  ( Sum(..), Product(..) )

import GHC.Generics

  ( Generic )

-- generic-data

import Generic.Data

  ( GenericProduct(..) )

-- groups

import Data.Group

  ( Group(..) )

-- groups-generic

import Data.Group.Generics

  ( ) -- imports generic instances

-----------------------------------------------------

data Point2D a = Point2D !a !a

  deriving stock Generic

newtype Vector2D a = Vector2D { tip :: Point2D a }

  deriving ( Semigroup, Monoid, Group )

    via GenericProduct ( Point2D ( Sum a ) )

data MyRecord

  = MyRecord

  { field1 :: Sum Double

  , field2 :: Product Double

  , field3 :: ( Sum Int, Sum Int )

  }

  deriving stock Generic

  deriving ( Semigroup, Monoid, Group )

    via GenericProduct MyRecord

```