https://github.com/totbwf/omit-generics

Omit fields for instance deriving
https://github.com/totbwf/omit-generics

ghc-generics haskell

Last synced: about 1 month ago
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Omit fields for instance deriving

• Host: GitHub
• URL: https://github.com/totbwf/omit-generics
• Owner: TOTBWF
• License: bsd-3-clause
• Created: 2020-06-05T01:24:37.000Z (almost 5 years ago)
• Default Branch: master
• Last Pushed: 2020-06-05T01:39:22.000Z (almost 5 years ago)
• Last Synced: 2025-03-28T14:21:44.490Z (2 months ago)
• Topics: ghc-generics, haskell
• Language: Haskell
• Size: 6.84 KB
• Stars: 37
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.org
  • Changelog: ChangeLog.md
  • License: LICENSE

Awesome Lists containing this project

README

        
* omit-generics

  =omit-generics= aims to make deriving ~Eq~ and ~Ord~ instances

  easier by giving the programmer control over what fields to ignore.

  This is best explained by an example:

  #+BEGIN_SRC haskell :multi-line t

    {-# LANGUAGE DataKinds #-}

    {-# LANGUAGE DeriveGeneric #-}

    {-# LANGUAGE DerivingStrategies #-}

    {-# LANGUAGE DerivingVia #-}

    import GHC.Generics

    import GHC.Generics.Omit

    data Person = Person { name :: String, age :: Int, metadata :: [String] }

        deriving stock Generic

        deriving Eq via (Omit '["age", "metadata"] Person)

  #+END_SRC

  Now, when we compare ~Person~ for equality, the ~age~ and ~metadata~

  fields are ignored!

  #+BEGIN_SRC haskell

    Person "Steve" 43 ["loves cats"] == Person "Steve" 1 ["loves dogs", "is a baby"]

    > True

  #+END_SRC