proposition: Lemma mmapE p i : msize p <= i -> p^[f,h] = \sum_(m : 'X_{1..n < i}) (f p@_m) * m^[h].
proof: Proof. move=> le_pi; set I : subFinType _ := 'X_{1..n < i}. rewrite /mmap (big_mksub I) ?msupp_uniq //=; first last. by move=> x /msize_mdeg_lt /leq_trans; apply. rewrite big_rmcond //= => j /memN_msupp_eq0 ->. by rewrite raddf0 mul0r. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(order fingroup perm ssralg zmodp poly ssrint) mathcomp(matrix vector) mathcomp(bigenough) ssrcomplements freeg