fact: Definition from_associational n (p:list (Z*Z)) := List.fold_right (fun t ls => dlet p := place t (pred n) in add_to_nth (fst p) (snd p) ls ) (zeros n) p.
imports: Coq.ZArith.ZArith Coq.Lists.List Coq.Setoids.Setoid Coq.Classes.Morphisms Coq.QArith.QArith_base Coq.QArith.Qreduction Coq.QArith.Qround