title: How to transpose a matrix in prolog
body: <p>How can I transpose a list like <code>[[1,2,3][4,5,6][6,7,8]]</code> to <code>[[1,4,6],[2,7,8],[3,6,9]]</code>?</p>
  
  <p>To depict it: I'd like to flip the matrix 90 degree to the left. How can I do that?</p>