title: Dot product in GUSEK/GLPK
body: <p>I've been trying to do a dot product in GUSEK. I used the explicit expression to compute it :</p>
  
  <pre><code>sum{i in 1..n} v[i]*x[i]
  </code></pre>
  
  <p>Is there a lighter notation I could use?</p>