[問題] boost regex的match

[apenptt (筆)]

想請問對boost regex有研究的前輩

我在boost regex的手冊裡看到一個範例
if(boost::regex_match(text, what, e, boost::match_extra))
{
unsigned i, j;
std::cout << "** Match found **\n Sub-Expressions:\n";
for(i = 0; i < what.size(); ++i)
cout << " $" << i << " = \"" << what[i] << "\"\n";
}

當text="aBBcccDDDDDeeeeeeee"

RE=(([[:lower:]]+)|([[:upper:]]+))+"

得到what中的內容:

$0 = "aBBcccDDDDDeeeeeeee"
$1 = "eeeeeeee"
$2 = "eeeeeeee"
$3 = "DDDDD"

不懂的是為什麼what[1]是印出eeeeeeee

what[1]存放的是符合第一個括號的東西吧?!

麻煩前輩指點一二，感激不盡!!

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