code: function nextLine() {
              var at;
              line += 1;
              if (line >= lines.length) {
                  return false;
              }
              character = 0;
              s = lines[line];
              at = s.search(cx);
              if (at >= 0) {
                  warningAt("Unsafe character.", line, at);
              }
              return true;
          }
docs: Private lex methods