English
The image of finsupp-sum under toFinsupp equals the skew-moniodal algebra sum: (⟨Finsupp.sum f g⟩) = sum ⟨f⟩ (⟨g · ·⟩).
Русский
Изображение Finsupp.sum под toFinsupp равно сумме в SkewMonoidAlgebra: (⟨Finsupp.sum f g⟩) = sum ⟨f⟩ (⟨g · ·⟩).
LaTeX
$$$\\langle \\mathrm{Finsupp.sum}\, f\, g \\rangle = \\sum \\langle f \\rangle (\\langle g \\cdot \\cdot \\rangle)$$$
Lean4
theorem ofFinsupp_sum {k' G' : Type*} [AddCommMonoid k'] (f : G →₀ k) (g : G → k → G' →₀ k') :
(⟨Finsupp.sum f g⟩ : SkewMonoidAlgebra k' G') = sum ⟨f⟩ (⟨g · ·⟩) := by apply toFinsupp_injective;
simp only [toFinsupp_sum']