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feat(AlgebraicTopology): order relation between simplices of the nerve of a partial order - #41656

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feat(AlgebraicTopology): order relation between simplices of the nerve of a partial order#41656
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@joelriou

@joelriou joelriou commented Jul 12, 2026

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This is applied to the characterization of the order relation between simplices of Δ[p] ⊗ Δ[q].


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@joelriou joelriou added the t-algebraic-topology Algebraic topology label Jul 12, 2026
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github-actions Bot commented Jul 12, 2026

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PR summary c3c290a347

Import changes for modified files

No significant changes to the import graph

Import changes for all files
Files Import difference

Declarations diff (regex)

+ image_le_image_iff
+ isoNerve_hom_app_obj
+ nerve_ofSimplex_le_ofSimplex_iff
+ ofSimplex_le_ofSimplex_iff
+ preimage_image
+ preimage_monotone
+ range_isoNerve_hom_app_obj

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 c3c290a).

  • +7 new declarations
  • −0 removed declarations
+PartialOrder.nerve_ofSimplex_le_ofSimplex_iff
+SSet.Subcomplex.image_le_image_iff
+SSet.Subcomplex.preimage_image
+SSet.Subcomplex.preimage_monotone
+SSet.prodStdSimplex.isoNerve_hom_app_obj
+SSet.prodStdSimplex.ofSimplex_le_ofSimplex_iff
+SSet.prodStdSimplex.range_isoNerve_hom_app_obj

No changes to strong technical debt.

No changes to weak technical debt.

Current commit c3c290a347
Reference commit cd580e54f1

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 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).

@joelriou joelriou added the WIP Work in progress label Jul 12, 2026
Comment thread Mathlib/AlgebraicTopology/SimplicialSet/Subcomplex.lean
Comment thread Mathlib/AlgebraicTopology/SimplicialSet/Subcomplex.lean
@robin-carlier robin-carlier added the awaiting-author A reviewer has asked the author a question or requested changes. label Jul 15, 2026
@joelriou joelriou removed the awaiting-author A reviewer has asked the author a question or requested changes. label Jul 16, 2026
@joelriou

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Thanks @robin-carlier for the reviews!

@robin-carlier

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Thanks!

maintainer merge

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🚀 Pull request has been placed on the maintainer queue by robin-carlier.

@mathlib-triage mathlib-triage Bot added the maintainer-merge A reviewer has approved the changed; awaiting maintainer approval. label Jul 16, 2026
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