code: function mpn_add(r, n1, n2, l) {
  	var c = 0;
  	for (var i = 0; i < l; ++i) {
  		r[i] = (c = (c >>> 31) + n1[i] + n2[i]) & 0x7FFFFFFF;
  	}
  	return c >>> 31;
  }
docs: /*
  Adds two multi-precision integers n1 and n2, stores their sum into r, and
  returns whether the addition overflowed (i.e., returns the "carry-out bit").