proposition: Lemma f1 (d : t) : \sum_(a in A) d a = 1.
proof: Proof. by case: d => ? /= /andP[? /eqP]. Qed.
imports: mathcomp(all_ssreflect ssralg fingroup perm matrix) mathcomp(all_algebra vector reals normedtype) mathcomp(mathcomp_extra boolp) mathcomp(Rstruct) ssrR logb realType_ext ssr_ext ssralg_ext bigop_ext