Semigroups/Monoids/Groups with absorbing elements
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Description
I recently had a need for a Monoid and Group which also have an absorbing element a defined by
combine(a, x) === combine(x, a) === a
These seem to go by various names, including "monoid/group with zero", "0-group", and "binoid".
Might they find a home in the cats hierarchy?
For reference, my current implementations: Binoid (laws) and Group0 (laws).
Edit: In fact, this hierarchy should probably start from a semigroup with an absorbing element (Semigroup0?).
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reviewing the referenced schrodinger/Binoid.scala and Group0.scala implementations and their BinoidLaws.scala and Group0Laws.scala files, then compare the proposed concepts with Cats' existing hierarchy. Done would require a decided placement and corresponding implementation and laws, but the issue does not identify the Cats files or a settled design.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- scala
- Domain
- backend-api-design
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 30/100