English
The formal derivative is defined as a derivation from the power-series ring to itself, satisfying linearity and Leibniz rule.
Русский
Формальная производная определяется как производная из кольца степенных рядов в себя, удовлетворяющая линейности и правилу Лейбница.
LaTeX
$$$ \\text{PowerSeries.derivative} : \\text{Derivation } R \\; (\\mathbb{R}[[X]]) \\to \\mathbb{R}[[X]] $$$
Lean4
/-- The formal derivative of a formal power series -/
noncomputable def derivative : Derivation R R⟦X⟧ R⟦X⟧
where
toFun := derivativeFun
map_add' := derivativeFun_add
map_smul' := derivativeFun_smul
map_one_eq_zero' := derivativeFun_one
leibniz' := derivativeFun_mul