Additional lemmas about homomorphisms of semirings and rings #
These lemmas were in Mathlib/Algebra/Hom/Ring/Defs.lean
and have now been deprecated.
@[deprecated "Use range_eq_singleton_iff and codomain_trivial_iff_range_trivial" (since := "2025-06-09")]
theorem
RingHom.codomain_trivial_iff_range_eq_singleton_zero
{α : Type u_1}
{β : Type u_2}
{x✝ : NonAssocSemiring α}
{x✝¹ : NonAssocSemiring β}
(f : α →+* β)
:
f : α →+* β
has a trivial codomain iff its range is {0}
.