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    <div class="moz-cite-prefix">Op 30-6-2012 1:38, Neil Van Dyke
      schreef:<br>
    </div>
    <blockquote cite="mid:4FEE3C65.6070809@neilvandyke.org" type="cite">Stephen
      Bloch wrote at 06/29/2012 06:01 PM:
      <br>
      <blockquote type="cite">Either you introduce this stuff much
        better than I do, or your students are much sharper.
        <br>
      </blockquote>
      <br>
      For the possible benefit of any students reading, I think someone
      say it, rather than leave it implied: Or the difference could be
      an isolated effect of, say, some subtle difference in how one
      concept was first introduced in their respective educations, not a
      reflection on the instruction or students overall.
      <br>
      <br>
      Aside: I think students are much the same everywhere, and most all
      students have potential to be good at this stuff.&nbsp; But learning
      this stuff well requires a lot of work, and I think students
      generally do need to have sufficient sense that they're ``sharp,''
      so that they stick with it and put in the necessary work.&nbsp; Or,
      there is another category of person, who sees themself as slow but
      determined; that will also lead to learning the stuff, if the self
      image gets them to put in the necessary work.&nbsp; (However, the ones
      who are self-assured and yet who don't do the learning work...
      they are doomed to be dim and to have few job options other than
      some kind of politician.)
      <br>
      <br>
      Neil V.
      <br>
      <br>
      ____________________
      <br>
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      <br>
    </blockquote>
    <br>
    <br>
    Im rereading the chapter and I think I found a piece of the puzzle.
    <br>
    <br>
    In the chapter there is a mention of this : <br>
    <br>
    <table class="RktBlk" cellspacing="0">
      <tbody>
        <tr>
          <td><span class="RktCmt">;</span><span class="RktCmt"> </span><span
              class="RktCmt">A </span><a name="(tech._mix._sig)"></a><span
              style="font-style: italic;">SIGS</span><span
              class="RktCmt"> (short for </span><span class="RktCmt">&#8220;</span><span
              class="RktCmt">space invader game state</span><span
              class="RktCmt">&#8221;</span><span class="RktCmt">) is one of: </span></td>
        </tr>
        <tr>
          <td><span class="RktCmt">;</span><span class="RktCmt"> </span><span
              class="RktCmt">&#8211;</span><span class="RktCmt"> </span><span
              class="RktPn">(</span><span class="RktSym">make-aim</span><span
              class="stt"> </span><a class="techoutside"
              href="#%28tech._mix._ufo%29" pltdoc="x"><span
                class="techinside">UFO</span></a><span class="stt"> </span><a
              class="techoutside" href="#%28tech._mix._tank%29"
              pltdoc="x"><span class="techinside">Tank</span></a><span
              class="RktPn">)</span></td>
        </tr>
        <tr>
          <td><span class="RktCmt">;</span><span class="RktCmt"> </span><span
              class="RktCmt">&#8211;</span><span class="RktCmt"> </span><span
              class="RktPn">(</span><span class="RktSym">make-fired</span><span
              class="stt"> </span><a class="techoutside"
              href="#%28tech._mix._ufo%29" pltdoc="x"><span
                class="techinside">UFO</span></a><span class="stt"> </span><a
              class="techoutside" href="#%28tech._mix._tank%29"
              pltdoc="x"><span class="techinside">Tank</span></a><span
              class="stt"> </span><a class="techoutside"
              href="#%28tech._mix._missile%29" pltdoc="x"><span
                class="techinside">Missile</span></a><span class="RktPn">)</span></td>
        </tr>
      </tbody>
    </table>
    <br>
    <br>
    I can do the same for my problem.<br>
    <br>
    ; A Vanimal is one of :<br>
    ; - (make-Vcat ( x happiness) <br>
    ;&nbsp;&nbsp; (make-Vcham ( x happiness) <br>
    <br>
    So Vanimal is not a struct but strictly a name.<br>
    <br>
    Am I on the right track. <br>
    <br>
    Roelof<br>
    <br>
    <br>
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