https://github.com/fumieval/covalent

heterogenous traversal
https://github.com/fumieval/covalent

Last synced: 23 days ago
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heterogenous traversal

• Host: GitHub
• URL: https://github.com/fumieval/covalent
• Owner: fumieval
• Created: 2022-01-21T09:05:48.000Z (almost 3 years ago)
• Default Branch: master
• Last Pushed: 2022-01-21T09:14:08.000Z (almost 3 years ago)
• Last Synced: 2024-10-15T06:50:58.951Z (2 months ago)
• Language: Haskell
• Size: 1.95 KB
• Stars: 3
• Watchers: 4
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md

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README

        
Covalent: heterogenous traversal

----

`Covalent` is an analogue of `Traversal` where its targets may be any type satisfying the specified constraint.

```haskell

class Covalent c a where

  traverseCommon :: Applicative f => (forall x. c x => x -> f x) -> a -> f a

```

An instance of `Covalent` can be generically derived as long as _all_ the fields satisfy the constraint:

```haskell

data Numeral = NumInt Int | NumDouble Double | NumPair Double Int deriving Generic

instance Covalent Show Numeral

instance Covalent Num Numeral

```

Using the `Covalen Num Numeral` instance, you can write a function that adds 1 regardless of the constructor.

```haskell

add1 :: Numeral -> Numeral

add1 = overCommon @Num (+1)

```