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feat(Combinatorics/SimpleGraph): define the Zarankiewicz function#34633

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feat(Combinatorics/SimpleGraph): define the Zarankiewicz function#34633
mitchell-horner wants to merge 7 commits intoleanprover-community:masterfrom
mitchell-horner:zarankiewicz

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@mitchell-horner mitchell-horner commented Jan 31, 2026 •
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Defines the Zarankiewicz function $z(m, n; s, t)$ in terms of bipartite graphs.

This comes from splitting up #25841 into smaller PRs.

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@mitchell-horner mitchell-horner changed the title feat(Combinatorics/SimpleGraph): define the Zarankiewicz function $z(m, n; s, t)$ feat(Combinatorics/SimpleGraph): define the Zarankiewicz function Jan 31, 2026
@github-actions github-actions bot added the t-combinatorics Combinatorics label Jan 31, 2026
@mitchell-horner mitchell-horner mentioned this pull request Jan 31, 2026
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github-actions bot commented Jan 31, 2026 •
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PR summary 478d4a1c4b

Import changes for modified files

No significant changes to the import graph

Import changes for all files
Files Import difference
Mathlib.Combinatorics.SimpleGraph.Extremal.Zarankiewicz (new file) 1088

Declarations diff

+ completeBipartiteGraph.congr
+ lt_zarankiewicz_iff
+ lt_zarankiewicz_iff_of_nonneg
+ two_mul_extremalNumber_le_zarankiewicz_symm
+ zarankiewicz
+ zarankiewicz_le_extremalNumber
+ zarankiewicz_le_iff
+ zarankiewicz_le_iff_of_nonneg
+ zarankiewicz_of_fintypeCard_eq

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

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

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

No changes to technical debt.

You can run this locally as

./scripts/reporting/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).

@mathlib4-dependent-issues-bot mathlib4-dependent-issues-bot added the blocked-by-other-PR This PR depends on another PR (this label is automatically managed by a bot) label Jan 31, 2026
b-mehta
b-mehta reviewed Jan 31, 2026
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Comment thread Mathlib/Combinatorics/SimpleGraph/Maps.lean Outdated
@mathlib-dependent-issues mathlib-dependent-issues bot removed the blocked-by-other-PR This PR depends on another PR (this label is automatically managed by a bot) label Mar 21, 2026
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mathlib-dependent-issues bot commented Mar 21, 2026

This PR/issue depends on:

@mathlib-merge-conflicts mathlib-merge-conflicts bot added the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Mar 21, 2026
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mathlib-merge-conflicts bot commented Mar 21, 2026

This pull request has conflicts, please merge master and resolve them.

@github-actions github-actions bot removed the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Mar 21, 2026
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