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[Merged by Bors] - feat(linear_algebra/free_module/ideal_quotient): add ideal.finrank_quotient_eq_sum #19084

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Co-authored-by: Junyan Xu junyanxumath@gmail.com


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@Multramate Multramate added awaiting-review The author would like community review of the PR awaiting-CI The author would like to see what CI has to say before doing more work. t-algebra Algebra (groups, rings, fields etc) labels May 24, 2023
@github-actions github-actions bot added the modifies-synchronized-file This PR touches a files that has already been ported to mathlib4, and may need a synchronization PR. label May 24, 2023
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Part of the auxiliary file in #18000

@github-actions github-actions bot removed the awaiting-CI The author would like to see what CI has to say before doing more work. label May 24, 2023
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Thanks, LGTM!

src/linear_algebra/free_module/pid.lean Outdated Show resolved Hide resolved
Co-authored-by: Junyan Xu <junyanxumath@gmail.com>
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Thanks!

maintainer merge

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🚀 Pull request has been placed on the maintainer queue by alreadydone.

Comment on lines +118 to +127
lemma ideal.finrank_quotient_eq_sum [nontrivial F]
[∀ i, module.free F (R ⧸ ideal.span ({I.smith_coeffs b hI i} : set R))]
[∀ i, module.finite F (R ⧸ ideal.span ({I.smith_coeffs b hI i} : set R))] :
finite_dimensional.finrank F (S ⧸ I)
= ∑ i, finite_dimensional.finrank F (R ⧸ ideal.span ({I.smith_coeffs b hI i} : set R)) :=
begin
rw [linear_equiv.finrank_eq $ ideal.quotient_equiv_direct_sum F b hI,
finite_dimensional.finrank_direct_sum]
-- slow, and dot notation doesn't work
end
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This lemma might look unnecessary but I just tested and it can't be inlined in finrank_quotient_span_eq_nat_degree_norm in #18000.

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Thanks!

bors merge

@github-actions github-actions bot added ready-to-merge All that is left is for bors to build and merge this PR. (Remember you need to say `bors r+`.) and removed awaiting-review The author would like community review of the PR labels May 28, 2023
bors bot pushed a commit that referenced this pull request May 28, 2023
…otient_eq_sum (#19084)

Co-authored-by: Junyan Xu <junyanxumath@gmail.com>
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bors bot commented May 28, 2023

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@bors bors bot changed the title feat(linear_algebra/free_module/ideal_quotient): add ideal.finrank_quotient_eq_sum [Merged by Bors] - feat(linear_algebra/free_module/ideal_quotient): add ideal.finrank_quotient_eq_sum May 28, 2023
@bors bors bot closed this May 28, 2023
@bors bors bot deleted the finrank_quotient_eq_sum branch May 28, 2023 16:51
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@Multramate, before you make many more mathlib3 PRs, please forward-port this and your other four changes (two PRs) on https://leanprover-community.github.io/mathlib-port-status/out-of-sync

Multramate added a commit to leanprover-community/mathlib4 that referenced this pull request Jun 7, 2023
Multramate added a commit to leanprover-community/mathlib4 that referenced this pull request Jun 7, 2023
Comment on lines +611 to +614
instance (F : Type u) [comm_ring F] [algebra F R] (b : basis ι R S) {I : ideal S} (hI : I ≠ ⊥) (i) :
module F (R ⧸ ideal.span ({I.smith_coeffs b hI i} : set R)) :=
by apply_instance -- quotient.module' _

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What was the purpose of adding this instance if apply_instance can already find it?

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See #19084 (comment)

It's weird we need to add a shortcut instance that is already found by typeclass inference.

bors bot pushed a commit to leanprover-community/mathlib4 that referenced this pull request Jun 9, 2023
bors bot pushed a commit to leanprover-community/mathlib4 that referenced this pull request Jun 10, 2023
…4820)

[`linear_algebra.free_module.pid`@`210657c4ea4a4a7b234392f70a3a2a83346dfa90`..`d87199d51218d36a0a42c66c82d147b5a7ff87b3`](https://leanprover-community.github.io/mathlib-port-status/file/linear_algebra/free_module/pid?range=210657c4ea4a4a7b234392f70a3a2a83346dfa90..d87199d51218d36a0a42c66c82d147b5a7ff87b3)



Co-authored-by: Junyan Xu <junyanxu.math@gmail.com>
qawbecrdtey pushed a commit to qawbecrdtey/greedoid-mathlib4 that referenced this pull request Jun 12, 2023
qawbecrdtey pushed a commit to qawbecrdtey/greedoid-mathlib4 that referenced this pull request Jun 12, 2023
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4 participants