fact: Definition UniqueFilterOfList (ls : list W) (P : W -> bool) : list W := FunctionOfList (fun x xs => if P x then (x::xs) else xs) nil ls.
imports: Coq.Strings.String Coq.Sets.Ensembles Coq.Sets.Finite_sets Coq.Lists.List Coq.Sorting.Permutation Coq.Classes.RelationPairs Fiat.ADT Fiat.ADT.ComputationalADT Fiat.ADTRefinement.Core Fiat.ADTNotation Fiat.ADTRefinement.GeneralRefinements Fiat.Computation Fiat.Common Fiat.Common.Ensembles Fiat.Common.Ensembles.Tactics Fiat.ComputationalEnsembles Fiat.FiniteSetADTs.FiniteSetADTMethodLaws Fiat.FiniteSetADTs.FiniteSetADT