code: function bnpRShiftTo(n, r) {
    r.s = this.s;
    var ds = Math.floor(n / this.DB);
    if (ds >= this.t) {
      r.t = 0;
      return;
    }
    var bs = n % this.DB;
    var cbs = this.DB - bs;
    var bm = (1 << bs) - 1;
    r[0] = this[ds] >> bs;
    for (var i = ds + 1; i < this.t; ++i) {
      r[i - ds - 1] |= (this[i] & bm) << cbs;
      r[i - ds] = this[i] >> bs;
    }
    if (bs > 0) r[this.t - ds - 1] |= (this.s & bm) << cbs;
    r.t = this.t - ds;
    r.clamp();
  }
docs: (protected) r = this >> n