Boost C++ Libraries of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

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#include <boost/pattern_except.hpp>

The class regex_error defines the type of objects thrown as exceptions to report errors during the conversion from a string representing a regular expression to a finite state machine.

namespace boost{

class regex_error : public std::runtime_error
   explicit regex_error(const std::string& s, regex_constants::error_type err, std::ptrdiff_t pos);
   explicit regex_error(boost::regex_constants::error_type err);
   boost::regex_constants::error_type code()const;
   std::ptrdiff_t position()const;

typedef regex_error bad_pattern; // for backwards compatibility
typedef regex_error bad_expression; // for backwards compatibility

} // namespace boost
regex_error(const std::string& s, regex_constants::error_type err, std::ptrdiff_t pos);
regex_error(boost::regex_constants::error_type err);

Effects: Constructs an object of class regex_error.

boost::regex_constants::error_type code()const;

Effects: returns the error code that represents parsing error that occurred.

std::ptrdiff_t position()const; 

Effects: returns the location in the expression where parsing stopped.

Footnotes: the choice of std::runtime_error as the base class for regex_error is moot; depending upon how the library is used exceptions may be either logic errors (programmer supplied expressions) or run time errors (user supplied expressions). The library previously used bad_pattern and bad_expression for errors, these have been replaced by the single class regex_error to keep the library in synchronization with the Technical Report on C++ Library Extensions.