leanprover / leanprover/reference-manual
Document `monotonicity_by`
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Description
In lean4#14861, coinductive predicates support was extended with a keyword monotonicity_by that allows the user to explicitly provide the monotonicity proof:
mutual
coinductive tick : Prop where
| mk : ¬tock → tick
monotonicity_by repeat monotonicity
inductive tock : Prop where
| mk : ¬tick → tock
end
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 locating the reference-manual section covering coinductive predicates and the syntax introduced in lean4#14861. Document the monotonicity_by keyword using the issue's mutual tick/tock example, including how it supplies the monotonicity proof; done when a reader can understand and use this syntax from the manual.
Written by the indexing model from the issue text.
Assessment
- Domain
- documentation
- Issue type
- Documentation
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Activity status
- Active
- Clarity
- Mostly clear
- Newbie friendliness
- 68/100