English
There is a canonical algebra homomorphism from the direct sum of submodules to the ambient algebra R.
Русский
Существует каноническое алгебра-гомоморфизм from прямого суммирования в алгебру R.
LaTeX
$$$$ DirectSum.co eAlgHom(A) : (⨁ i, A_i) \to_{algebra S} R. $$$$
Lean4
/-- The canonical algebra isomorphism between `⨁ i, A i` and `R`. -/
def coeAlgHom [AddMonoid ι] [CommSemiring S] [Semiring R] [Algebra S R] (A : ι → Submodule S R)
[SetLike.GradedMonoid A] : (⨁ i, A i) →ₐ[S] R :=
DirectSum.toAlgebra S _ (fun i => (A i).subtype) rfl (fun _ _ => rfl)