fact: Definition mxrow m (B_ : forall j, 'M[T]_(m, q_ j)) := \matrix_(j, k) B_ (sig1 k) j (sig2 k).
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg countalg finalg zmodp)