Section 9.6: fix Exercise 9.6.1 statements and add Exercise 9.6.2#488
Merged
teorth merged 1 commit intoteorth:mainfrom Apr 21, 2026
Merged
Section 9.6: fix Exercise 9.6.1 statements and add Exercise 9.6.2#488teorth merged 1 commit intoteorth:mainfrom
teorth merged 1 commit intoteorth:mainfrom
Conversation
Contributor
rkirov
commented
Apr 19, 2026
rkirov
commented
- Exercise 9.6.1 c): add parens around the two ¬ ∃ conjuncts (without them, ∧ associates inside the inner ¬ ∃ body, changing the meaning).
- Exercise 9.6.1 b): change domain from (1, 2) to [0, ∞), matching the textbook's unbounded-domain counterexample.
- Split Exercise 9.6.1 docstring labels into a) / b) / c) / d).
- Add Exercise 9.6.2: BddOn.add, BddOn.sub, BddOn.mul, and BddOn.div (the last as a Decidable, since divisibility of the bounded class is the actual question).
- Exercise 9.6.1 c): add parens around the two ¬ ∃ conjuncts (without them, ∧ associates inside the inner ¬ ∃ body, changing the meaning). - Exercise 9.6.1 b): change domain from (1, 2) to [0, ∞), matching the textbook's unbounded-domain counterexample. - Split Exercise 9.6.1 docstring labels into a) / b) / c) / d). - Add Exercise 9.6.2: BddOn.add, BddOn.sub, BddOn.mul, and BddOn.div (the last as a Decidable, since divisibility of the bounded class is the actual question). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
rkirov
commented
Apr 19, 2026
| example : ∃ f: ℝ → ℝ, BddOn f (.Icc (-1) 1) ∧ | ||
| ¬ ∃ x₀ ∈ Set.Icc (-1) 1, IsMinOn f (.Icc (-1) 1) x₀ ∧ | ||
| ¬ ∃ x₀ ∈ Set.Icc (-1) 1, IsMaxOn f (.Icc (-1) 1) x₀ | ||
| (¬ ∃ x₀ ∈ Set.Icc (-1) 1, IsMinOn f (.Icc (-1) 1) x₀) ∧ |
Contributor
Author
There was a problem hiding this comment.
this one was subtle, without parens lean reads it as ¬ (A ∧ ¬ B)
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.