function validate_fields(form, field_names, message) {
  var pattern = /^-*$/;
  for (var i in field_names) {
    var val = form[field_names[i]].value;
    if (val == null || val == "" || pattern.test(val)) {
      alert(message);
      return false;
    }
  }
  return true;
}

function validate_required_fields(form) {
  var pattern = /^required[_-].*/;
  for (var prop in form) {
    if (pattern.test(prop)) {
      if (form[prop].value != null && form[prop].value == "") {
        alert("Please complete all required fields.");
        return false;
      }
    }
  }
  return true;
}

function validate_checked(name, message) {
  var buttons = document.getElementsByName(name);
  for (var i=0; i<buttons.length; ++i) {
    if (buttons[i].checked)
      return true;
  }
  alert(message);
  return false;
}