title: Cross-product matrix in Eigen
body: <p>Is there a ready function or method in Eigen for the <a href="http://en.wikipedia.org/wiki/Hat_operator#Cross_product" rel="nofollow noreferrer">Hat operator</a>? That is the operator, taking a vector as input and returning a matrix, which mimics a cross product with that vector. I know, that it can be easily written, but would like to avoid it:</p>
  <pre><code>Eigen::Vector3d t = // some vector ;
  Eigen::Matrix3d t_hat;
  t_hat &lt;&lt; 0, -t(2), t(1),
      t(2), 0, -t(0),
      -t(1), t(0), 0;
  </code></pre>