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feat(RingTheory/Ideal/Colon): add a few API lemmas (leanprover-community#34060)
This PR adds a few missing API lemmas to `RingTheory/Ideal/Colon`. Co-authored-by: tb65536 <thomas.l.browning@gmail.com>
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Mathlib/RingTheory/Ideal/Colon.lean

Lines changed: 15 additions & 3 deletions
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@@ -65,8 +65,6 @@ theorem bot_colon : colon (⊥ : Submodule R M) (N : Set M) = N.annihilator := b
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ext x
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simp [mem_colon, mem_annihilator]
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@[deprecated (since := "2026-01-11")] alias colon_bot := bot_colon
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theorem colon_mono (hn : N₁ ≤ N₂) (hs : S₁ ⊆ S₂) : N₁.colon S₂ ≤ N₂.colon S₁ :=
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fun _ hrns ↦ mem_colon.mpr fun s₁ hs₁ ↦ hn <| (mem_colon).mp hrns s₁ <| hs hs₁
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@@ -95,6 +93,11 @@ lemma inf_colon : (N₁ ⊓ N₂).colon S = N₁.colon S ⊓ N₂.colon S := by
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lemma iInf_colon {ι : Sort*} (f : ι → Submodule R M) : (⨅ i, f i).colon S = ⨅ i, (f i).colon S := by
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aesop (add simp mem_colon)
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@[simp]
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lemma colon_finsetInf {ι : Type*} (s : Finset ι) (f : ι → Submodule R M) :
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(s.inf f).colon S = s.inf (fun i ↦ (f i).colon S) := by
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aesop (add simp mem_colon)
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@[simp]
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lemma top_colon : (⊤ : Submodule R M).colon S = ⊤ := by
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aesop (add simp mem_colon)
@@ -111,17 +114,26 @@ lemma colon_iUnion {ι : Sort*} (f : ι → Set M) : N.colon (⋃ i, f i) = ⨅
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lemma colon_empty : N.colon (∅ : Set M) = ⊤ := by
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aesop (add simp mem_colon)
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lemma colon_singleton_zero : N.colon {0} = ⊤ := by
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simp
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lemma colon_bot : N.colon ((⊥ : Submodule R M) : Set M) = ⊤ := by
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simp
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end Semiring
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section CommSemiring
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variable [CommSemiring R] [AddCommMonoid M] [Module R M]
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variable {N : Submodule R M} {S : Set M}
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variable {N N' : Submodule R M} {S : Set M}
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@[deprecated mem_colon (since := "2026-01-15")]
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theorem mem_colon' {r} : r ∈ N.colon S ↔ S ≤ comap (r • (LinearMap.id : M →ₗ[R] M)) N :=
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mem_colon
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theorem mem_colon_iff_le {r} : r ∈ N.colon N' ↔ r • N' ≤ N := by
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aesop (add simp SetLike.coe_subset_coe)
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/-- A variant for arbitrary sets in commutative semirings -/
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theorem bot_colon' : (⊥ : Submodule R M).colon S = (span R S).annihilator := by
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aesop (add simp [mem_colon, mem_annihilator_span])

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