English
Substitution of a multivariate power series into a power series can be packaged as an algebra homomorphism.
Русский
Подстановка многомерного степенного ряда в ряд выражается как алгебраическая однородная отображение.
LaTeX
$$Substitution by a can be encoded as an algebra homomorphism PowerSeries R →ₐ[R] MvPowerSeries τ S.$$
Lean4
/-- Substitution of power series into a power series. -/
noncomputable def subst (a : MvPowerSeries τ S) (f : PowerSeries R) : MvPowerSeries τ S :=
MvPowerSeries.subst (fun _ ↦ a) f