feat: Fodor's lemma#37685
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PR summary af2e27d2c7Import changes exceeding 2%
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| File | Base Count | Head Count | Change |
|---|---|---|---|
| Mathlib.SetTheory.Cardinal.Cofinality.Club | 726 | 765 | +39 (+5.37%) |
Import changes for all files
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Mathlib.SetTheory.Cardinal.Cofinality.Club |
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Declarations diff (regex)
+ ciSup_mem
+ diag
+ exists_isStationary_preimage_singleton
You can run this locally as follows
## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
## summary with just the declaration names:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh <optional_commit>
## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.
Declarations diff (Lean)
✅ Lean-aware diff — post-build, computed from the Lean environment (commit
af2e27d).
- +3 new declarations
- −0 removed declarations
+IsClub.ciSup_mem
+IsClub.diag
+exists_isStationary_preimage_singletonNo changes to strong technical debt.
No changes to weak technical debt.
Current commit af2e27d2c7
Reference commit 6c5a9081e9
This script lives in the mathlib-ci repository. To run it locally, from your mathlib4 directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
../mathlib-ci/scripts/reporting/technical-debt-metrics.sh pr_summary
- The
relativevalue is the weighted sum of the differences with weight given by the inverse of the current value of the statistic. - The
absolutevalue is therelativevalue divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).
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YaelDillies
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| protected theorem diag [IsRegularCardinalOrder α] {f : α → Set α} (hα : cof α ≠ ℵ₀) | ||
| (hf : ∀ a, IsClub (f a)) : IsClub {a | ∀ b < a, a ∈ f b} where |
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What's diagonal about this? Mayve worth giving the lemma a more syntactic name?
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It's called diagonal intersection in Kunen's book (page 220).
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Yeah, this is one of those circumstances where I think a more explicit name would just obfuscate what the lemma says.
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Co-authored-by: Yaël Dillies <yael.dillies@gmail.com>
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We define stationary sets and prove Fodor's lemma, following the proof at Wikipedia.
I'm surprised that this has a Wikipedia article but isn't listed in 1000.yaml. Is it just because the name has "lemma" instead of "theorem"?