leanprover / leanprover/reference-manual
Minor typo in CH14. mapConst documentation
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Description
Describe the error
The Lean Language Reference, Ch 14. type class : Functor
Given a : α and v : f α, mapConst a v is equivalent to Function.const _ a <$> v. For some functors, this can be implemented more efficiently; for all other functors, the default implementation may be used.
Here, I think that the type of v must be f $\beta$ ( or f _ )
The VScode Lean extensions also display same description, but if my understanding is correct, the second argument of Functor.mapConst must be the domain instance of constant function ( $f \beta \rightarrow f \alpha$ ) so the type of v must be f $\beta$.
Thank you,
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Research direction
Start with the quoted Lean Language Reference, Chapter 14 entry for Functor.mapConst and verify its type against the referenced Function.const description. Update the documentation so the type of v is represented accurately, then check the rendered reference and the corresponding VS Code Lean extension wording if that text is shared.
Written by the indexing model from the issue text.
Assessment
- Domain
- documentation
- Issue type
- Documentation
- Difficulty
- 1/5
- Estimated time
- Under an hour
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 52/100