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## Struct template basic_regex

boost::xpressive::basic_regex — Class template basic_regex<> is a class for holding a compiled regular expression.

## Synopsis

    // In header: <boost/xpressive/xpressive_fwd.hpp>

    template<typename BidiIter>
    struct basic_regex {
      // construct/copy/destruct
      basic_regex();
      basic_regex(basic_regex< BidiIter > const &);
      template<typename Expr> basic_regex(Expr const &);
      basic_regex< BidiIter > & operator=(basic_regex< BidiIter > const &);
      template<typename Expr> basic_regex< BidiIter > & operator=(Expr const &);

      // public member functions
      std::size_t mark_count() const;
      regex_id_type regex_id() const;
      void swap(basic_regex< BidiIter > &);

      // public static functions
      template<typename InputIter>
        static basic_regex< BidiIter >
        compile(InputIter, InputIter, flag_type = regex_constants::ECMAScript);
      template<typename InputRange>
        static basic_regex< BidiIter >
        compile(InputRange const &, flag_type = regex_constants::ECMAScript);
      static basic_regex< BidiIter >
      compile(char_type const *, flag_type = regex_constants::ECMAScript);
      static basic_regex< BidiIter >
      compile(char_type const *, std::size_t, flag_type);
    };

## Description

### `basic_regex` public construct/copy/destruct

1.     basic_regex();

   Postconditions: | regex_id() == 0
   Postconditions: | mark_count() == 0

2.     basic_regex(basic_regex< BidiIter > const & that);

   Parameters: |
   `that` | The `basic_regex` object to copy.
   Postconditions: | regex_id() == that.regex_id()
   Postconditions: | mark_count() == that.mark_count()

3.     template<typename Expr> basic_regex(Expr const & expr);

   Construct from a static regular expression.

   Parameters: |
   `expr` | The static regular expression
   Requires: | Expr is the type of a static regular expression.
   Postconditions: | regex_id() != 0
   Postconditions: | mark_count() >= 0

4.     basic_regex< BidiIter > & operator=(basic_regex< BidiIter > const & that);

   Parameters: |
   `that` | The `basic_regex` object to copy.
   Postconditions: | regex_id() == that.regex_id()
   Postconditions: | mark_count() == that.mark_count()
   Returns: | *this

5.     template<typename Expr> basic_regex< BidiIter > & operator=(Expr const & expr);

   Construct from a static regular expression.

   Parameters: |
   `expr` | The static regular expression.
   Requires: | Expr is the type of a static regular expression.
   Postconditions: | regex_id() != 0
   Postconditions: | mark_count() >= 0
   Returns: | *this
   Throws: | std::bad_alloc on out of memory

### `basic_regex` public member functions

1.     std::size_t mark_count() const;

   Returns the count of capturing sub-expressions in this regular expression

2.     regex_id_type regex_id() const;

   Returns a token which uniquely identifies this regular expression.

3.     void swap(basic_regex< BidiIter > & that);

   Swaps the contents of this `basic_regex` object with another.

   | Note
   This is a shallow swap that does not do reference tracking. If you embed a `basic_regex` object by reference in another regular expression and then swap its contents with another `basic_regex` object, the change will not be visible to the enclosing regular expression. It is done this way to ensure that swap() cannot throw.

   Parameters: |
   `that` | The other `basic_regex` object.
   Throws: | Will not throw.

### `basic_regex` public static functions

1.     template<typename InputIter>
         static basic_regex< BidiIter >
         compile(InputIter begin, InputIter end,
                 flag_type flags = regex_constants::ECMAScript);

   Factory method for building a regex object from a range of characters. Equivalent to `regex_compiler`< BidiIter >().compile(begin, end, flags);

   Parameters: |
   `begin` | The beginning of a range of characters representing the regular expression to compile.
   `end` | The end of a range of characters representing the regular expression to compile.
   `flags` | Optional bitmask that determines how the pat string is interpreted. (See syntax_option_type.)
   Requires: | [begin,end) is a valid range.
   Requires: | The range of characters specified by [begin,end) contains a valid string-based representation of a regular expression.
   Returns: | A basic_regex object corresponding to the regular expression represented by the character range.
   Throws: | regex_error when the range of characters has invalid regular expression syntax.

2.     template<typename InputRange>
         static basic_regex< BidiIter >
         compile(InputRange const & pat,
                 flag_type flags = regex_constants::ECMAScript);

   This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

3.     static basic_regex< BidiIter >
       compile(char_type const * begin,
               flag_type flags = regex_constants::ECMAScript);

   This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

4.     static basic_regex< BidiIter >
       compile(char_type const * begin, std::size_t len, flag_type flags);

   This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.