https://github.com/danr/genifunctors

Generate generalized fmap, foldMap and traverse
https://github.com/danr/genifunctors

Last synced: about 1 year ago
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Generate generalized fmap, foldMap and traverse

• Host: GitHub
• URL: https://github.com/danr/genifunctors
• Owner: danr
• License: bsd-3-clause
• Created: 2013-09-07T17:19:55.000Z (almost 13 years ago)
• Default Branch: master
• Last Pushed: 2016-11-14T10:26:05.000Z (over 9 years ago)
• Last Synced: 2024-10-28T14:09:27.309Z (over 1 year ago)
• Language: Haskell
• Homepage: https://hackage.haskell.org/package/genifunctors
• Size: 37.1 KB
• Stars: 5
• Watchers: 5
• Forks: 2
• Open Issues: 2
• Metadata Files:
  • Readme: README.md
  • Changelog: changelog
  • License: LICENSE

Awesome Lists containing this project

README

          
Generate (derive) generalized `fmap`, `foldMap` and `traverse` for `Bifunctors`,

`Trifunctors`, or a functor with any arity

Example:

    data U a b c d

        = L [U a b c d]               -- polymorphic recursion

        | M (V (a,b) (Either c d))    -- mutually recursive

        | a :+: Int                   -- infix syntax, record syntax, type synonyms

        | R { c :: c, d :: String }   -- and primitive data types supported

    data V u v = X (U v v u u) | Z u

    fmapU :: (a -> a') -> (b -> b') -> (c -> c') -> (d -> d') ->

             U a b c d -> U a' b' c' d'

    fmapU = $(genFmap ''U)

    foldU :: Monoid m => (a -> m) -> (b -> m) -> (c -> m) -> (d -> m) ->

             U a b c d -> m

    foldU = $(genFoldMap ''U)

    travU :: Applicative f =>

             (a -> f a') -> (b -> f b') -> (c -> f c') -> (d -> f d') ->

             U a b c d -> f (U a' b' c' d')

    travU = $(genTraverse ''U)