lean-ja / lean-ja/lean-by-example
DecidableEq は deriving できないのに BEq はできる例
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コード例
- Dominant language
- Lean
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Description
variable {α : Type} [DecidableEq α]
/-- ラベル付き二分木 -/
inductive Tree (α : Type) where
/-- 空の木 -/
| empty
| node (v : α) (children : List (Tree α))
/- None of the deriving handlers for class `DecidableEq` applied to Tree -/
deriving DecidableEq, BEq
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 shown Tree example in the repository's Lean examples or build setup. Check whether the mismatch between deriving DecidableEq and BEq is expected or a bug; done means the issue has a confirmed explanation and the appropriate example, documentation, or compiler behavior is updated.
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
- Needs clarification
- Newbie friendliness
- 25/100