Nested ?: is hard to read due to the precedence. It's better to spend a few lines and break it up:

   return a < b
          ? -1
          : a > b
            ? 1
            : 0;

If that is too much:

   return a < b
          ? -1
          : a > b ? 1 : 0;

Other possibilities:

   return a < b ? -1
                : a > b ? 1
                        : 0;

   return a < b ? -1
                : a > b ? 1 : 0;