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[Merged by Bors] - feat(Topology/Compactness): delta-generated spaces#19431

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DeltaGeneratedSpace
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[Merged by Bors] - feat(Topology/Compactness): delta-generated spaces#19431
peabrainiac wants to merge 11 commits intomasterfrom
DeltaGeneratedSpace

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@peabrainiac peabrainiac commented Nov 24, 2024 •
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Introduces delta-generated topological spaces and shows that they are sequential, locally path-connected and closed under disjoint unions and quotients.

That spaces like ℝ are delta-generated will be shown in a later PR, by proving that every locally path-connected first-countable space is delta-generated. The proof of that is a bit nontrivial, so I've chosen not to include it in this already long PR.

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github-actions bot commented Nov 24, 2024 •
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PR summary f467536889

Import changes for modified files

No significant changes to the import graph

Import changes for all files
Files Import difference
Mathlib.Topology.Compactness.DeltaGeneratedSpace (new file) 1692

Declarations diff

+ DeltaGeneratedSpace
+ DeltaGeneratedSpace.coinduced
+ DeltaGeneratedSpace.continuous_iff
+ DeltaGeneratedSpace.iSup
+ DeltaGeneratedSpace.isOpen_iff
+ DeltaGeneratedSpace.sup
+ Quot.deltaGeneratedSpace
+ Quotient.deltaGeneratedSpace
+ Sigma.deltaGeneratedSpace
+ Sum.deltaGeneratedSpace
+ TopologicalSpace.deltaGenerated
+ Topology.IsQuotientMap.deltaGeneratedSpace
+ continuous_counit
+ continuous_to_deltaGenerated
+ counit
+ deltaGeneratedSpace_deltaGenerated
+ deltaGenerated_deltaGenerated_eq
+ deltaGenerated_eq_coinduced
+ deltaGenerated_le
+ deltaGenerated_mono
+ eq_deltaGenerated
+ instance : DeltaGeneratedSpace (of X)
+ instance : TopologicalSpace (of X) := deltaGenerated X
+ instance [DeltaGeneratedSpace X] : LocPathConnectedSpace X := by
+ instance [DeltaGeneratedSpace X] : SequentialSpace X := by
+ isOpen_deltaGenerated_iff
+ of

You can run this locally as follows 
## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary
  • The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
  • The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

@github-actions github-actions bot added t-topology Topological spaces, uniform spaces, metric spaces, filters new-contributor This PR was made by a contributor with at most 5 merged PRs. Welcome to the community! labels Nov 24, 2024
grunweg
grunweg reviewed Nov 25, 2024
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peabrainiac and others added 2 commits November 25, 2024 17:49
@peabrainiac @grunweg
fix formatting
9d47778 
Co-authored-by: grunweg <rothgami@math.hu-berlin.de>
@peabrainiac
fix copyright header typo
f467536
@peabrainiac peabrainiac mentioned this pull request Nov 26, 2024
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kim-em
kim-em reviewed Nov 26, 2024
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Mathlib/Topology/Compactness/DeltaGeneratedSpace.lean
Comment on lines +140 to +142
omit tY in
/-- Any topology coinduced by a delta-generated topology is delta-generated. -/
lemma DeltaGeneratedSpace.coinduced [DeltaGeneratedSpace X] (f : X → Y) :
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Suggested change
omit tY in
/-- Any topology coinduced by a delta-generated topology is delta-generated. -/
lemma DeltaGeneratedSpace.coinduced [DeltaGeneratedSpace X] (f : X → Y) :
/-- Any topology coinduced by a delta-generated topology is delta-generated. -/
lemma DeltaGeneratedSpace.coinduced {Y} [DeltaGeneratedSpace X] (f : X → Y) :

should also work. This makes a "fresh" Y local to this lemma, so the instance isn't pulled in.

Stylistic preference up to you, though.

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@peabrainiac peabrainiac Nov 26, 2024 •
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That is indeed also the style I usually go for - I just thought omit would make slightly more sense here because it doesn't mess with the order of Y and tX as implicit arguments. I suppose it doesn't really matter either way though

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kim-em commented Nov 26, 2024

Thanks, this looks great!

bors d+

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mathlib-bors bot commented Nov 26, 2024

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

@ghost ghost added the delegated This pull request has been delegated to the PR author (or occasionally another non-maintainer). label Nov 26, 2024
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peabrainiac commented Nov 26, 2024

Thank you for the quick review 😄

bors r+

mathlib-bors bot pushed a commit that referenced this pull request Nov 26, 2024
@peabrainiac
feat(Topology/Compactness): delta-generated spaces (#19431)
84b0984 
Introduces delta-generated topological spaces and shows that they are sequential, locally path-connected and closed under disjoint unions and quotients.



Co-authored-by: peabrainiac <43812953+peabrainiac@users.noreply.github.com>
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mathlib-bors bot commented Nov 26, 2024

Pull request successfully merged into master.

Build succeeded:

@mathlib-bors mathlib-bors bot changed the title feat(Topology/Compactness): delta-generated spaces [Merged by Bors] - feat(Topology/Compactness): delta-generated spaces Nov 26, 2024
@mathlib-bors mathlib-bors bot closed this Nov 26, 2024
@mathlib-bors mathlib-bors bot deleted the DeltaGeneratedSpace branch November 26, 2024 23:14
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