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[Merged by Bors] - feat: Density of a finset#11243

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YaelDillies wants to merge 5 commits intomasterfrom
finset_density
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[Merged by Bors] - feat: Density of a finset#11243
YaelDillies wants to merge 5 commits intomasterfrom
finset_density

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The density of a finite set in an ambient group is a quantity of great interest in combinatorics.
This PR defines Finset.dens s for s : Finset α as the size of s divided by the size of α, with value in any semifield.
The API lemmas are copied from Finset.card (but not all Finset.card lemmas are sensible Finset.dens lemmas).

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@urkud
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urkud commented May 5, 2024

See also commProb which you may want to port to the new definition. Also, do you plan to link it to the measure theory probability w.r.t. the uniform distribution?

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See also commProb which you may want to port to the new definition.

Nice observation! Will do so in a later PR.

do you plan to link it to the measure theory probability w.r.t. the uniform distribution?

Maybe in a distant future but right now I don't need it.

The density of a finite set in an ambient group is a quantity of great interest in combinatorics.
This PR defines `Finset.dens s` for `s : Finset α` as the size of `s` divided by the size of `α`, with value in any semifield.
The API lemmas are copied from `Finset.card` (but not all `Finset.card` lemmas are sensible `Finset.dens` lemmas).

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github-actions bot commented Jun 9, 2024

PR summary 8241efc7a4

Import changes for modified files

Dependency changes

File Base Count Head Count Change
Mathlib.Tactic.Positivity.Finset 488 538 +50 (+10.25%)
Import changes for all files
Files Import difference
3 files Mathlib.Combinatorics.SimpleGraph.Triangle.Removal Mathlib.Combinatorics.Additive.Corner.Roth Mathlib.Tactic
1
Mathlib.Combinatorics.SimpleGraph.Triangle.Basic Mathlib.Combinatorics.SimpleGraph.Triangle.Tripartite 6
Mathlib.Tactic.Positivity.Finset 50
Mathlib.Data.Finset.Density 537

Declarations diff

+ dens
+ dens_cons
+ dens_disjUnion
+ dens_empty
+ dens_eq_card_div_card
+ dens_eq_one
+ dens_eq_zero
+ dens_filter_add_dens_filter_not_eq_dens
+ dens_inter_add_dens_sdiff
+ dens_inter_add_dens_union
+ dens_le_dens
+ dens_le_dens_sdiff_add_dens
+ dens_lt_dens
+ dens_map_le
+ dens_mono
+ dens_ne_one
+ dens_ne_zero
+ dens_pos
+ dens_sdiff
+ dens_sdiff_add_dens
+ dens_sdiff_add_dens_eq_dens
+ dens_sdiff_add_dens_inter
+ dens_sdiff_comm
+ dens_singleton
+ dens_strictMono
+ dens_union_add_dens_inter
+ dens_union_le
+ dens_union_of_disjoint
+ dens_univ
+ evalFinsetDens
+ le_dens_sdiff
+ they
++ ⟨_,

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

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

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@Ruben-VandeVelde Ruben-VandeVelde left a comment

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Feel free to put on the maintainer queue regardless of your response to my comment below, as long as you're convinced.

@Ruben-VandeVelde Ruben-VandeVelde added awaiting-author A reviewer has asked the author a question or requested changes. and removed awaiting-review labels Jul 5, 2024
@YaelDillies YaelDillies added awaiting-review and removed awaiting-author A reviewer has asked the author a question or requested changes. labels Jul 6, 2024
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Thanks 🎉

bors merge

mathlib-bors bot pushed a commit that referenced this pull request Jul 12, 2024
The density of a finite set in an ambient group is a quantity of great interest in combinatorics.
This PR defines `Finset.dens s` for `s : Finset α` as the size of `s` divided by the size of `α`, with value in any semifield.
The API lemmas are copied from `Finset.card` (but not all `Finset.card` lemmas are sensible `Finset.dens` lemmas).

From LeanAPAP
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mathlib-bors bot commented Jul 12, 2024

This PR was included in a batch that was canceled, it will be automatically retried

mathlib-bors bot pushed a commit that referenced this pull request Jul 12, 2024
The density of a finite set in an ambient group is a quantity of great interest in combinatorics.
This PR defines `Finset.dens s` for `s : Finset α` as the size of `s` divided by the size of `α`, with value in any semifield.
The API lemmas are copied from `Finset.card` (but not all `Finset.card` lemmas are sensible `Finset.dens` lemmas).

From LeanAPAP
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mathlib-bors bot commented Jul 12, 2024

Pull request successfully merged into master.

Build succeeded:

@mathlib-bors mathlib-bors bot changed the title feat: Density of a finset [Merged by Bors] - feat: Density of a finset Jul 12, 2024
@mathlib-bors mathlib-bors bot closed this Jul 12, 2024
@mathlib-bors mathlib-bors bot deleted the finset_density branch July 12, 2024 15:30
@adomani adomani mentioned this pull request Aug 1, 2024
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7 participants