Characteristic of semirings #
@[simp]
theorem
CharP.cast_card_eq_zero
(R : Type u_1)
[AddGroupWithOne R]
[Fintype R]
:
↑(Fintype.card R) = 0
theorem
CharP.char_ne_zero_of_finite
(R : Type u_1)
[NonAssocRing R]
(p : ℕ)
[CharP R p]
[Finite R]
:
p ≠ 0
The characteristic of a finite ring cannot be zero.
theorem
CharP.char_is_prime
(R : Type u_1)
[Ring R]
[NoZeroDivisors R]
[Nontrivial R]
[Finite R]
(p : ℕ)
[CharP R p]
:
p.Prime
theorem
charP_of_ne_zero
(R : Type u_1)
[NonAssocRing R]
[Fintype R]
(n : ℕ)
(hn : Fintype.card R = n)
(hR : ∀ i < n, ↑i = 0 → i = 0)
:
CharP R n