[/ 
  Copyright 2006-2007 John Maddock.
  Distributed under the Boost Software License, Version 1.0.
  (See accompanying file LICENSE_1_0.txt or copy at
  http://www.boost.org/LICENSE_1_0.txt).
]


[section:bad_expression bad_expression]

[h4 Synopsis]

   #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
   {
   public:
      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

[h4 Description]

   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and `bad_expression` for errors, these have been replaced by the single 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 
[tr1].

[endsect]