typelevel / typelevel/cats

Removing MonoidK and SemigroupK

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#1,932 6 comments 0 reactions 0 assignees View on GitHub

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Blocked Source Breaking
Dominant language
Scala
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Merged PRs (30d)
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Description

This depends on newtypes; without newtypes, we can't really do this.

As far as I can see, no evidence has been presented that MonoidK and SemigroupK are useful abstractions. So far, all they exist to do is disambiguate instances of monoid and semigroup, which is the job of newtypes, and they do a worse job because they don't compose with ordinary monoids and semigroups; there is no implicit product of a Monoid with a MonoidK.

Edit: They also don't disambiguate instances well. There's two valid MonoidK's for Option, for example.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

No files, tests, or entry points are identified in the issue. Start by reviewing the dependency on newtypes and the MonoidK/SemigroupK abstractions; done would require a decided removal plan and corresponding project changes.

Written by the indexing model from the issue text.

Assessment

Tech stack
scala
Domain
tooling
Issue type
Refactor
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
15/100

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