[Merged by Bors] - feat(Combinatorics/SimpleGraph): add simp lemma getVert_map for Walk.map

[maix00]

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• in concept similar to List.getElem_map
• deserve a simp lemma (useful when pushing walks between Subgraphs)

lemma getVert_map (i : ℕ) : (p.map f).getVert i = f (p.getVert i) := by
revert u; induction i with
| zero => simp
| succ => intro _ p; cases p <;> simp [*]

can not just use simp to prove this fact

[github-actions]

PR summary f90d4e66f7

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

+ getVert_map

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).

[ocfnash]

Thanks!

bors merge

[mathlib-bors]

Pull request successfully merged into master.

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