anchor.diff:                  let a_path = a.A1Path()
                   a_path = path
               ) refs
  -        | None -> raise (ParseException formula)
  +        | None,false -> raise (ParseException formula)
  +        | None,true -> Seq.empty    // just ignore parse exceptions for now
   
       // This is the one you want to call from user code
       let ParseFormula(str, path, wb, ws): AST.Expression =
  
positive.code:         | :? AST.ReferenceFunction as r -> [r.FunctionName]
          | _ -> []
  
      let GetSCFormulaNames(formula: string, path: string, ws: Worksheet, wb: Workbook) =
          let app = wb.Application
          let path' = System.IO.Path.GetDirectoryName(wb.FullName)
          match ExcelParser.ParseFormula(formula, path', wb, ws) with
          | Some(ast) -> GetFormulaNamesFromExpr(ast) |> Seq.ofList
          | None -> raise (ParseException formula)
  
      let GetSingleCellReferencesFromFormula(formula: string, wb: Workbook, ws: Worksheet) : seq<AST.Address> =
          let app = wb.Application
          let path = System.IO.Path.GetDirectoryName(wb.FullName)
          match ExcelParser.ParseFormula(formula, path, wb, ws) with
          | Some(tree) ->
              // temporarily bail if a refers to object in a different workbook
              // TODO: we should open the other workbook and continue the analysis
              let refs = GetSCExprRanges(tree) |> Seq.ofList
  
negative.code: //        let target_wbs = target_ref.GetWorkbookNames()
  //        Seq.fold (fun acc wbname -> acc && cur_wb.Name = wbname) true target_wbs
  
      let GetReferencesFromFormula(formula: string, wb: Workbook, ws: Worksheet, ignore_parse_errors: bool) : seq<XLRange> =
          let wbpath = System.IO.Path.GetDirectoryName(wb.FullName)
          let app = wb.Application
          try
              match ExcelParser.ParseFormula(formula, wbpath, wb, ws),ignore_parse_errors with
              | Some(tree),_ ->
                  let refs = GetExprRanges(tree)
                  List.map (fun (r: AST.Range) ->
                              // temporarily bail if r refers to object in a different workbook
  