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[Merged by Bors] - chore(LinearAlgebra/Matrix): deprecate Matrix.star_mul #38307

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[Merged by Bors] - chore(LinearAlgebra/Matrix): deprecate Matrix.star_mul #38307

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chore(LinearAlgebra/Matrix): deprecate `Matrix.star_mul`
Vierkantor Apr 20, 2026
9d8dfb4
Merge remote-tracking branch 'upstream/master' into Matrix.star_mul-d…
Vierkantor Apr 21, 2026
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7 changes: 2 additions & 5 deletions Mathlib/LinearAlgebra/Matrix/ConjTranspose.lean
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Expand Up @@ -424,14 +424,11 @@ instance [Star α] [Star β] [SMul α β] [StarModule α β] : StarModule α (Ma
star_smul := conjTranspose_smul

/-- When `α` is a `*`-(semi)ring, `Matrix.star` is also a `*`-(semi)ring. -/
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instance [Fintype n] [NonUnitalSemiring α] [StarRing α] : StarRing (Matrix n n α) where
instance [Fintype n] [NonUnitalNonAssocSemiring α] [StarRing α] : StarRing (Matrix n n α) where
star_add := conjTranspose_add
star_mul := conjTranspose_mul

/-- A version of `star_mul` for `*` instead of `*`. -/
theorem star_mul [Fintype n] [NonUnitalNonAssocSemiring α] [StarRing α] (M N : Matrix n n α) :
star (M * N) = star N * star M :=
conjTranspose_mul _ _
@[deprecated (since := "2026-04-20")] protected alias star_mul := StarMul.star_mul

end Star

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