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## Class template period_parser

boost::date_time::period_parser — Not a facet, but a class used to specify and control period parsing.

## Synopsis

    // In header: <boost/date_time/period_parser.hpp>

    template<typename date_type, typename CharT>
    class period_parser {
    public:
      // types
      typedef std::basic_string< CharT >                string_type;
      typedef CharT                                     char_type;
      typedef std::istreambuf_iterator< CharT >         stream_itr_type;
      typedef string_parse_tree< CharT >                parse_tree_type;
      typedef parse_tree_type::parse_match_result_type  match_results;
      typedef std::vector< std::basic_string< CharT > > collection_type;

      enum period_range_option { AS_OPEN_RANGE, AS_CLOSED_RANGE };

      // construct/copy/destruct
      period_parser(period_range_option = AS_CLOSED_RANGE,
                    const char_type *const = default_period_separator,
                    const char_type *const = default_period_start_delimeter,
                    const char_type *const = default_period_open_range_end_delimeter,
                    const char_type *const = default_period_closed_range_end_delimeter);
      period_parser(const period_parser< date_type, CharT > &);

      // public member functions
      period_range_option range_option() const;
      void range_option(period_range_option);
      collection_type delimiter_strings() const;
      void delimiter_strings(const string_type &, const string_type &,
                             const string_type &, const string_type &);
      template<typename period_type, typename duration_type, typename facet_type>
        period_type get_period(stream_itr_type &, stream_itr_type &,
                               std::ios_base &, const period_type &,
                               const duration_type &, const facet_type &) const;

      // private member functions
      void consume_delim(stream_itr_type &, stream_itr_type &,
                         const string_type &) const;

      // public data members
      static const char_type default_period_separator;
      static const char_type default_period_start_delimeter;
      static const char_type default_period_open_range_end_delimeter;
      static const char_type default_period_closed_range_end_delimeter;
    };

## Description

Provides settings for the following:

- period_separator – default '/'

- period_open_start_delimeter – default '['

- period_open_range_end_delimeter – default ')'

- period_closed_range_end_delimeter – default ']'

- display_as_open_range, display_as_closed_range – default closed_range

For a typical date_period, the contents of the input stream would be

    [2004-Jan-04/2004-Feb-01]

where the date format is controlled by the date facet

### `period_parser` public construct/copy/destruct

1.     period_parser(period_range_option range_opt = AS_CLOSED_RANGE,
                     const char_type *const period_separator = default_period_separator,
                     const char_type *const period_start_delimeter = default_period_start_delimeter,
                     const char_type *const period_open_range_end_delimeter = default_period_open_range_end_delimeter,
                     const char_type *const period_closed_range_end_delimeter = default_period_closed_range_end_delimeter);

   Constructor that sets up period parser options.

2.     period_parser(const period_parser< date_type, CharT > & p_parser);

### `period_parser` public member functions

1.     period_range_option range_option() const;

2.     void range_option(period_range_option option);

3.     collection_type delimiter_strings() const;

4.     void delimiter_strings(const string_type & separator,
                              const string_type & start_delim,
                              const string_type & open_end_delim,
                              const string_type & closed_end_delim);

5.     template<typename period_type, typename duration_type, typename facet_type>
         period_type get_period(stream_itr_type & sitr, stream_itr_type & stream_end,
                                std::ios_base & a_ios, const period_type &,
                                const duration_type & dur_unit,
                                const facet_type & facet) const;

   Generic code to parse a period – no matter the period type.

   This generic code will parse any period using a facet to to get the 'elements'. For example, in the case of a date_period the elements will be instances of a date which will be parsed according the to setup in the passed facet parameter.

   The steps for parsing a period are always the same:

   - consume the start delimiter

   - get start element

   - consume the separator

   - get either last or end element depending on range settings

   - consume the end delimeter depending on range settings

   Thus for a typical date period the contents of the input stream might look like this:

       [March 01, 2004/June 07, 2004]   <-- closed range
       [March 01, 2004/June 08, 2004)   <-- open range

### `period_parser` private member functions

1.     void consume_delim(stream_itr_type & sitr, stream_itr_type & stream_end,
                          const string_type & delim) const;

   throws ios_base::failure if delimiter and parsed data do not match