func str(a []PlumType) (PlumType, error) { return printer.Pr_list(a, false, "", "", ""), nil }
func println(a []PlumType) (PlumType, error) { fmt.Println(printer.Pr_list(a, false, "", "", " ")) return nil, nil }
func pr_str(a []PlumType) (PlumType, error) { return printer.Pr_list(a, true, "", "", " "), nil }