title: How to contract two tensors in Maxima?
body: <p>With the package <code>itensor</code> I can contract tensors using indices, but how do I contract two tensors if I have the components? For example, if I try to contract the following tensors:</p>
  
  <pre><code>load("itensor");
  m: matrix([1,2],[3,4]);
  l: matrix([5,6],[7,8]);
  
  show(m([],[i,j])*l([i,j],[]));
  </code></pre>
  
  <p>nothing is displayed.</p>