English
For a principal ideal ring α and a nonzero ideal P ≠ ⊥, P is prime iff there exists p with P = span{p} and p prime.
Русский
Для кольца с Principal идеалами α и неравноправного P ≠ ⊥, P prime тогда и только тогда, когда существует p: P = span{p} и p prime.
LaTeX
$$$P.IsPrime \\iff \\exists p, Prime p \\land P = \\operatorname{span}\\{p\\}.$$$
Lean4
theorem isPrime_iff_of_isPrincipalIdealRing {P : Ideal α} (hP : P ≠ ⊥) : P.IsPrime ↔ ∃ p, Prime p ∧ P = span { p }
where
mp
h := by
obtain ⟨p, rfl⟩ := Submodule.IsPrincipal.principal P
exact ⟨p, (span_singleton_prime (by simp [·] at hP)).mp h, rfl⟩
mpr := by
rintro ⟨p, hp, rfl⟩
rwa [span_singleton_prime (by simp [hp.ne_zero])]