[boost] Why my subexpression doesn't work in Regex

Subject: [boost] Why my subexpression doesn't work in Regex
From: Qihong Wang (qihongwang_at_[hidden])
Date: 2009-03-17 22:33:12

Hello,

I'm a new boost and regex user.  I tried a c++ regex sample as follows

  regex pattern("banan\\(an\\)*a");
  string   str =  "bananana";

  if(regex_match(str, pattern))
     cout<<"---- pattern matched ----"<<endl;
  else
     cout<<"---- pattern unmatched ----"<<endl;

To my surprise, the it printed out pattern unmatched. If I change str to
"banan(an)a",
the result is pattern matched. Feels like boost.Regex doesn't treat ( ) as
subexpression.
Any idea?

Thanks,

Qihong Wang