leanprover-community / leanprover-community/mathlib4
`notation3` doesn't support unparenthesized multiple binders like `Π₀ i j, δ i j`
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Description
This issue was found out in #13198.
The scoped binders in notation3 doesn't support unparenthesized multiple binders like Π₀ i j, δ i j.
The notation Π₀ i, β i is defined by the notation3 command, as notation3 "Π₀ "(...)", "r:(scoped f => DFinsupp f) => r.
When we use multiple binders on the notation3, we must parenthesize them like Π₀ (i) (j), δ i j. The parser doesn't recognize Π₀ i j, δ i j.
This is regression from Lean 3.
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 reproducing the notation3 behavior with Π₀ i j, δ i j and compare it with the parenthesized form Π₀ (i) (j), δ i j. Read the scoped-binder definition and parser behavior described in the issue. Done means unparenthesized multiple binders are accepted without regressing the existing notation.
Written by the indexing model from the issue text.
Assessment
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100