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[Merged by Bors] - feat(topology/metric_space/hausdorff_distance): add definition and lemmas about open thickenings of subsets #10188

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@kkytola kkytola commented Nov 5, 2021

Add definition and basic API about open thickenings of subsets in metric spaces, in preparation for the portmanteau theorem on characterizations of weak convergence of Borel probability measures.


This is a (rather independent) part of my attempt to PR a proof of the portmanteau theorem https://github.com/kkytola/lean_portmanteau. Specifically it is intended as an improved and cleaned up version of a manageable size chunck of the file https://github.com/kkytola/lean_portmanteau/blob/main/portmanteau_metric_lemmas.lean.

If this PR's style is the right way to do thickenings, then I will follow up by closed thickenings, intersections of thickenings in relation to closures, continuous approximations of indicator functions of closed sets, and crucially, the countability of thickening-radii such that the boundary of the thickening carries a positive measure w.r.t. a given Borel probability measure.

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@kkytola kkytola requested a review from sgouezel November 5, 2021 16:29
@kkytola kkytola added the awaiting-review The author would like community review of the PR label Nov 5, 2021
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This looks good to me, modulo a few minor comments. Could you also mention it in the file-level docstring?

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@sgouezel sgouezel added awaiting-author A reviewer has asked the author a question or requested changes and removed awaiting-review The author would like community review of the PR labels Nov 10, 2021
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kkytola commented Nov 12, 2021

This looks good to me, modulo a few minor comments. Could you also mention it in the file-level docstring?

I added a file-level docstring about the definition of thickening. There are not yet any substantial results besides very basic API around this definition. I plan to follow up by a bit more, in preparation for portmanteau and Lévy-Prokhorov metric. I will re-evaluate if the file-level docstring needs further updating then.

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kkytola commented Nov 12, 2021

I don't understand the failed check (CI / build mathlib (push)), this compiles on my computer.

@kkytola kkytola added awaiting-review The author would like community review of the PR and removed awaiting-author A reviewer has asked the author a question or requested changes labels Nov 12, 2021
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I have restarted the build

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kkytola commented Nov 13, 2021

I have restarted the build

Thank you! I still don't understand the new failure; now "CI / build mathlib (push)" works but "CI / run tests (push)" fails.

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bors d+

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bors bot commented Nov 15, 2021

✌️ kkytola can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

@github-actions github-actions bot added delegated The PR author may merge after reviewing final suggestions. and removed awaiting-review The author would like community review of the PR labels Nov 15, 2021
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kkytola commented Nov 16, 2021

bors r+

bors bot pushed a commit that referenced this pull request Nov 16, 2021
…mmas about open thickenings of subsets (#10188)

Add definition and basic API about open thickenings of subsets in metric spaces, in preparation for the portmanteau theorem on characterizations of weak convergence of Borel probability measures.



Co-authored-by: kkytola <39528102+kkytola@users.noreply.github.com>
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bors bot commented Nov 17, 2021

Pull request successfully merged into master.

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@bors bors bot changed the title feat(topology/metric_space/hausdorff_distance): add definition and lemmas about open thickenings of subsets [Merged by Bors] - feat(topology/metric_space/hausdorff_distance): add definition and lemmas about open thickenings of subsets Nov 17, 2021
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