fact: Definition pid_smith := gdco_smith (fun a b => projT1 (pid_gdco a b)).
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype matrix mxalgebra bigop zmodp perm choice) dvdring mxstructure minor stronglydiscrete coherent edr