!! +exec+ +loop+ +jump+
$lst_tit for$lst_titend$type_exec
  $(lst_syntax)for $emph var $emphend = $emph start $emphend to $emph end
  $emphend [step $emph st $emphend ]</tt> <br/>或<tt>
 $ !for $emph var $emphend from $emph start $emphend to $emph end $emphend
  [step $emph st $emphend ]</tt> <br/>或<tt>
 $ !for $emph var $emphend in $emph list$emphend<br/></tt>
  ... (多行内容)<br/>
  <tt>!next</tt>
  $lst_mean For循环. 在前两个格式里, $emph var $emphend 从
  $emph start$emphend 取到 $emph end$emphend, 具有可选的步长 $emph
  st$emphend. <br/>
  在第三种格式里, $emph var$emphend 逐次取遍表 $emph list$emphend 里的项.
  $emph list$emphend 是用逗号分隔的项的表. <br/>
  位于for循环内部的命令
  <pre>!break</pre>
  会打断循环. 本版本还没有 $emph continue $emphend 命令. <br/>
  建议把变量名 $emph var$emphend 加到
  <tt>!next </tt> 的行里. 这样做目前并无什么作用, 但在wims的将来版本里可能会有用.

