code: function(s, opts){
      var r = s.split('~').map(function(d){
        return parseFloat(d);
      });
      // number at position 1 must greater than position 0.
      if (r[0] > r[1]) {
        return r.reverse();
      }
      return r;
    }
docs: String like `1~2`, `5~8`, it means a range from a specific number to another.
  @param {String} s
  @param {Object} opts
  @returns {*}