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Mathlib.Algebra.Order.Positive.Ring

Algebraic structures on the set of positive numbers #

In this file we define various instances (AddSemigroup, OrderedCommMonoid etc) on the type {x : R // 0 < x}. In each case we try to require the weakest possible typeclass assumptions on R but possibly, there is a room for improvements.

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@[simp]
theorem Positive.coe_add {M : Type u_1} [AddMonoid M] [Preorder M] [AddLeftStrictMono M] (x y : { x : M // 0 < x }) :
↑(x + y) = x + y
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@[simp]
theorem Positive.val_mul {R : Type u_2} [StrictOrderedSemiring R] (x y : { x : R // 0 < x }) :
↑(x * y) = x * y
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@[simp]
theorem Positive.val_pow {R : Type u_2} [StrictOrderedSemiring R] (x : { x : R // 0 < x }) (n : ) :
↑(x ^ n) = x ^ n
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@[simp]
theorem Positive.val_one {R : Type u_2} [StrictOrderedSemiring R] :
1 = 1
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If R is a nontrivial linear ordered commutative semiring, then {x : R // 0 < x} is a linear ordered cancellative commutative monoid.

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