fact: Definition rcs_perm_ffun n : {ffun 'I_n.+1 -> 'I_n.+1} := [ffun x : 'I_n.+1 => if x == ord0 then ord_max else inord x.-1].
imports: mathcomp(all_ssreflect ssralg poly polydiv fingroup perm) mathcomp(finalg zmodp matrix mxalgebra mxpoly polydiv vector) ssralg_ext poly_ext f2 hamming linearcode dft