[Boost-users] Boost.Regex vs. Boost.Spirit

From: Boris (boriss_at_[hidden])
Date: 2008-04-01 09:20:12

Can anyone tell me why Boost.Spirit (which reuses Boost.Regex for regular  
expressions) works while the code below where Boost.Regex is used directly  
can not be compiled?

std::string in = "test";

boost::wregex expr(L"test");
boost::match_results<std::string::const_iterator> what;
boost::regex_search(in, what, expr); // COMPILER ERROR

std::string out;
boost::spirit::rxstrlit<wchar_t> expr2(L"test");
boost::spirit::parse(in.c_str(), expr2[boost::spirit::assign_a(out)]);

The basic problem is of course that the regular expressions are based on  
wchar_t while the input string is based on char. Thus I'm not so much  
surprised why Boost.Regex does not work. I'm much more surprised though  
that my compiler (VC++ 2008) doesn't report an error with the code above  
which uses Boost.Spirit.

I don't know why the code using Boost.Spirit compiles (is this  
implementation-dependent or guaranteed behavior)? It would make using  
regular expressions in templates much easier though as regular expressions  
don't seem to depend on the Char type of strings (assuming this is a  
feature I can rely on)?

Boris