default:
          return '';
      }
    }
  },
  
  reverse: function(tbody) {
    // reverse the rows in a tbody
    newrows = [];
    for (var i=0; i<tbody.rows.length; i++) {
      newrows[newrows.length] = tbody.rows[i];
    }
    for (var i=newrows.length-1; i>=0; i--) {
       tbody.appendChild(newrows[i]);
    }
    delete newrows;
  },
  
  /* sort functions
     each sort function takes two parameters, a and b
     you are comparing a[0] and b[0] */
  sort_numeric: function(a,b) {
    aa = parseF