fact: Definition isMarked (sig : Type) (s : sigTape sig) : bool := match s with | LeftBlank marked => marked | RightBlank marked => marked | NilBlank => true | MarkedSymbol _ => true | UnmarkedSymbol _ => false end.
imports: Undecidability.TM.Compound.TMTac Undecidability.TM.Code.Code Undecidability.TM.Basic.Mono Undecidability.TM.Compound.Multi