[Boost-users] [boost.xpressive] RE for replacing problem

From: Olaf Peter (ope-devel_at_[hidden])
Date: 2008-08-13 09:04:33

Hi,

my member function write() get called with string arguments like:

Hello
\n
World
\n
Traceback ...\n
NameError
:
  name ... not defined
\n

etc.

I want to add a prefix (a prompt '>>>' concete) so that the result will 
become:

 >>> Hello
 >>> World
 >>> Traceback ....
 >>> NameError: name ... not defined

Yes, this comes from redirected python output.

The simplest solution seems to use regex/xpressive:

     class redirector
     {
         const std::string m_prompt;
         const xpr::sregex m_re;
         const std::string m_re_fmt;

     public:
         redirector(const std::string& prompt = ">>> ")
             : m_prompt(prompt),
               m_re(xpr::sregex::compile("(\\n)!")),
               m_re_fmt(m_prompt + "\n")
         { }

         void write(const std::string& text) {

             std::cout << m_prompt
                       << xpr::regex_replace(text, m_re, m_re_fmt);
         }
     ...
     };

where my regex won't work. What is the correct one since I can get a 
single '\n', a terminated '\n' or multiline strings separated by '\n'. 
Is this approach good for this problem?

Anyway, I get a lot of warnings from constructor and write function, any 
ideas why?

Thanks,
Olaf