leanprover-community / leanprover-community/mathlib4
`auto_param`s for `volume` doing less than they used to
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Description
Per @urkud on #4628,
Lean 3 was able to apply, e.g., instances about
measure_theory.measure.prodto the volume on the Cartesian product. Lean 4 can't do this, so we need to duplicate many instances.
I believe this issue is not yet fully understood, but I'm recording it here for when someone has time to investigate.
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 with the discussion on #4628 and the linked Zulip thread, then investigate how Lean 4 handles auto_params for volume compared with Lean 3. The goal is for existing instances about measure_theory.measure.prod to apply to Cartesian-product volume without duplicating many instances.
Written by the indexing model from the issue text.
Assessment
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100