}             // func GetNextMember

            public override string ToString(PpsLuaRowEnvironment env)
            {
                try
                {
                    return(ProcsPps.ToString(GetNextMember(env.Row, 0), fmt) ?? String.Empty);
                }
                catch (Exception e)
                {
                    return("{EX=" + e.Message + "}");
                }
            }     // func ToString
            }             // ctor

            public override string ToString(PpsLuaRowEnvironment env)
            {
                try
                {
                    return(ProcsPps.ToString(chunk.Run(env)[0], fmt) ?? String.Empty);
                }
                catch (LuaRuntimeException e)
                {
                    return("{RE=" + e.Message + "}");
                }
                catch (Exception e)
                {
                    return("{EX=" + e.Message + "}");
                }
            }     // proc ToString