title: Import data from txt to Mathematica
body: <p>Consider the following list in mathematica:</p>
  
  <pre><code>a = {
     {
      {0, 0, 0}, {1, 0, 0}, {1, 1, 0}
      },
     {
      {0, 0, 1}, {1, 0, 1}, {1, 1, 1}
      }
     };
  </code></pre>
  
  <p>Now, invoke:</p>
  
  <pre><code>Export["test.dat", a]
  </code></pre>
  
  <p>and then</p>
  
  <pre><code>b = Import["test.dat"]
  </code></pre>
  
  <p>You will see that at the end <code>a</code> doesn't equal <code>b</code>. Should I consider this as a feature or a bug?</p>
  
  <p>Furthermore, I would like to import a list having the following format: <code>{P1,P2,P3...,Pn}</code> where <code>Pi={v1,v2,v3,...,vm}</code> and each <code>vi={x,y,z}</code> where <code>x,y,z</code> are numbers representing the coordinates of the vertex <code>vi</code>. This should be a list of polygons.</p>
  
  <p>How should I set my <code>.dat</code> file so I can read it with Mathematica, and how should I read it? I tried to imitate the output of <code>Export["test.dat",a]</code> above, but then I discovered the other issue. I found this <a href="https://stackoverflow.com/questions/1944453/how-to-import-data-from-a-file-as-list-array-in-mathematica">question</a>, but couldn't make the answer work for me...</p>
  
  <p>Any ideas? Thanks in advance!</p>