anchor.diff:            <dd><input class="regin" type="text" name="email" title="new email"
                        value="${(if email email "")}" /></dd>]
             (maybe-show-form-error error "pw" "Wrong password")
  -          #H[<dt><label for="password">Confirm password:</label></dt>
  +          #H[<dt><label for="password">Enter password:</label></dt>
             <dd><input class="regin" type="password" name="password" /></dd>
             <dt /><dd><input type="submit" value="change email" /></dd>
           </dl>
  
positive.code:           ((not (email-address? email))             (err "email"))
            ((check-password password *account*)
             (update-account *account*
                             account-email email)     #/site/preferences-ok)
            (t                                        (err "pw")))))
  
  (defpage /site/preferences "Account preferences" (email error)
    (if *account*
        (progn
          #H[<h3>Change account preferences</h3>
          <form id="changemail" class="prefs" method="post"
                action="$(#/site/change-email)">
          <dl>]
            (maybe-show-form-error error "email" "Bad email address")
  
negative.code:   </form>
  </div>])))
  
  (defun password? (pw)
    (and pw (not (< (length pw) 8))))
  
  (defun email-address? (str)
    (and str (not (string= str ""))))
  
  