fact: Definition findall_aux oi0 p s : (seq nat -> seq nat) * nat := foldl (fun '(s,i) x => (if p x then s \o cons i else s, i.+1)) oi0 s.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat seq path eqtype choice bigop) pcm(options prelude pred)