English
Let Q be a quadratic form on M. For a bilinear map f with the hf property, folding the generator ι_Q m under foldr' yields f m (1, n). In other words, foldr' Q f hf n (ι_Q m) = f m (1, n).
Русский
Пусть Q – квадратичная форма на M. Для f с hf, свёртка по генератору ι_Q m в foldr' даёт f m (1, n).
LaTeX
$$$\\foldr'_Q f hf n (\\iota_Q m) = f m (1, n)$$$
Lean4
@[simp]
theorem foldl_ι (f : M →ₗ[R] N →ₗ[R] N) (hf) (n : N) (m : M) : foldl Q f hf n (ι Q m) = f m n := by
rw [← foldr_reverse, reverse_ι, foldr_ι]