} while (--n); 
} 
  trace: function() {    if (!this.isSquare()) { return null; }    var tr = this.elements[0][0], n = this.elements.length - 1, k = n, i;    do { i = k - n + 1;      tr += this.elements[i][i];    } while (--n);    return tr;  },
3123	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/3123/5bb35ddb3516d7e68f3747d86540ffaa68de3fe3/matrix.js/buggy/src/matrix.js