fact: Definition prod_assoc_map f g := Lf(fun z => (Lg (domain g) (fun l => Vf (pr_j f (Vg g l)) z))) (productb f) (productf (domain g) (fun l => (restriction_product f (Vg g l)))).
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)