first集和last集以firstVT和lastVT的求法

Posted 2023-04-27

要求写出详细的定义 再详细解答两个例子 一定要写点文字描述的东西啊 就是、看不懂书上的答案
1.A->aT T->ABl|ε B->dB' B'->bB'|ε 求first集和last集
2.S->T|SVT T->U|T^U U->i|-U 求firstVT 和 lastVT集（V和^是交和并的意思）

参考技术A 这个真不懂本回答被提问者采纳

在块上添加“first”和“last”类

Sometimes, the first or last block in a region needs to be styled different than the rest. This solution do this in simple way for Drupal 6.
(originaly code from [email protected]: http://drupal.org/node/293188#comment-1282186)

<?php
function themename_preprocess_block(&$vars, $hook)
{
    static $counts;
    if(!isset($counts)) $counts = array();
    $region = $vars['block']->region;
    if(!isset($counts[$region])) $counts[$region] = count(block_list($region));
    $count = $counts[$region];
    $extremity = '';
    if($vars['id'] == 1) $extremity = 'first';
    if($vars['id'] == $count) $extremity = 'last';
    $vars['classes'] .= $extremity != '' ? ' ' . $extremity : '';
}
?>
 
You need to change themename to your themplate name.