fact: Definition crossR p := variation (sgp_minfty p) (sgp_pinfty p).
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq choice path fintype) mathcomp(div bigop order ssralg poly polydiv ssrnum perm zmodp ssrint) mathcomp(polyorder polyrcf interval matrix mxtens)