fact: Definition mid := fun (s : seq R) => (drop 1 (take (size s).-1 s)).
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path choice fintype order) mathcomp(prime div bigop ssralg poly polydiv polyorder ssrnum zmodp) mathcomp(polyrcf qe_rcf_th complex)