proposition: Lemma idem_sub_le_big (I : eqType) s s' P (F : I -> R) : {subset s <= s'} -> le (\big[op/x]_(i <- s | P i) F i) (\big[op/x]_(i <- s' | P i) F i).
proof: Proof. move=> ss'; rewrite -big_undup// -[X in le _ X]big_undup//. by rewrite uniq_sub_le_big ?undup_uniq// => i; rewrite !mem_undup; apply: ss'. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div fintype tuple finfun)