docs: function LSEQArray(s){
      this._s = s;
      this._c = 0;
      this._hash = function(depth) { return depth%2; };
  //    this._hash = function(depth) { return 0; };
  
      this._array = []; // array of couples {_e: element, _i: identifier}
      this._array[0] = new C(null, new ID(BI.int2bigInt(0,Base.getSumBit(0)),
  					[0], [0])); // lowest id
      this._array[1] = new C(null, new ID(BI.int2bigInt(Math.pow(2,Base._b)-1,
  						      Base.getSumBit(0)),
  					[Number.MAX_VALUE],
  					[Number.MAX_VALUE])); // highest id
      this.length = 0;
  }