English
If f is continuous multilinear, then the sum of f over sums of inputs equals the sum over all Finset-indexed combinations r: ∀ i, α_i.
Русский
Если f непрерывно мультилейно, сумма по входам, разбитым по Finset, равна сумме по всем комбинациям r.
LaTeX
$$$(f\, (\lambda i. \sum j\in A_i, g_i j)) = \sum_{r \in \Pi A} f(\lambda i. g_i(r_i)).$$$
Lean4
/-- Turn a continuous perfect pairing between `M` and `N` into a map from `M` to continuous linear
maps `N → R`. -/
noncomputable def toContPerfPair : M ≃ₗ[R] StrongDual R N :=
.ofBijective { toFun := _, map_add' x y := by ext; simp, map_smul' r x := by ext; simp } <|
IsContPerfPair.bijective_left p