code: function processExpr(exprObj, idx) {
      var randExpr = clubexpr.replaceValuesWith(exprObj.expr, clubexpr.randomNumbers(9));
      var link = '<a href="#e' + (idx+1) + '">' + (idx+1) + '.</a>';
      document.write('<h2 id="e' + (idx+1) + '">' + link + ' ' + exprObj.nom + '</h2>');
      document.write(clubexpr.renderExprAsLisp(randExpr));
      document.write("$$" + clubexpr.renderExprAsLaTeX(randExpr) + "$$");
      if (exprObj.conv.length) {
          document.write("conventions : ");
          document.write(exprObj.conv.join(', '));
      }
      var props = clubexpr.properties(randExpr);
      document.write("<h3>Inspection</h3>");
      document.write("nature: " + props.nature + "<br>");
      document.write(props.nbOps + " operation" + (props.nbOps>1?"(s)":"") + ": " +
                     props.ops.join(', ') + "<br>");
      document.write("unique ops: " + props.uniqueOps.join(', ') + "<br>");
      if (props.conventions.length) {
          document.write("computed conventions : ");
          document.write(props.conventions.join(', '));
          document.write("<br>");
      }
      document.write("depth: " + props.depth + "<br>");
      document.write("leaves: " + props.leaves + "<br>");
      document.write("letters: " + props.letters + "<br>");
      document.write("numbers: " + props.numbers + "<br>");
  }
docs: Callback for rendering each expression