title: Array of Tuples-IBM Cplex
body: <p>I have defined an array called <code>A</code> in IBM CPlex indexed over a set.</p>
  <p>The set is a set of edges in a graph such as <code>{&lt;1,2&gt;,&lt;1,3&gt;,...}</code>. Each edge is defined as a tuple.</p>
  <p>In the post-processing part, I put <code>writeln(A[&lt;1,2&gt;])</code> but I have got no idea why I can not get the amount of the related array element and I will face a strange error.</p>