fact: Definition strict_suffix x y l m := { a : _ & { b | (a <> nil \/ b <> nil) /\ l = a++x /\ m = b++y } }.
imports: List Undecidability.PCP.PCP Undecidability.PCP.Util.Facts Undecidability.Synthetic(Definitions DecidabilityFacts EnumerabilityFacts MoreEnumerabilityFacts ListEnumerabilityFacts) Coq.Init.Wf Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list utils_nat finite)