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perf(Algebra/Ring/Defs): unfold the new Semiring instances #39772

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perf(Algebra/Ring/Defs): unfold the new Semiring instances #39772

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18 changes: 15 additions & 3 deletions Mathlib/Algebra/Ring/Defs.lean
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Expand Up @@ -147,9 +147,21 @@ class Semiring (α : Type u) extends AddCommMonoid α, MonoidWithZero α, NonUni
class Ring (R : Type u) extends Semiring R, AddCommGroup R, AddGroupWithOne R

-- Add some short-cut instances to avoid going through the less used ring type classes.
instance [Semiring α] : Distrib α := inferInstance
instance [Semiring α] : MulZeroClass α := inferInstance
instance [Semiring α] : MulZeroOneClass α := inferInstance
instance [i : Semiring α] : Distrib α where
left_distrib := i.toDistrib.left_distrib
right_distrib := i.toDistrib.right_distrib

instance [i : Semiring α] : MulZeroClass α where
zero_mul := i.toMonoidWithZero.zero_mul
mul_zero := i.toMonoidWithZero.mul_zero

instance [i : Semiring α] : MulZeroOneClass α where
toMulOneClass := {
one_mul := i.toMulOneClass.one_mul
mul_one := i.toMulOneClass.mul_one }
zero_mul := i.toMonoidWithZero.zero_mul
mul_zero := i.toMonoidWithZero.mul_zero

attribute [instance] Semiring.toMonoid

/-!
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