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     Subject to the Boost Software License, Version 1.0. 
     (See accompanying file LICENSE_1_0.txt or  http://www.boost.org/LICENSE_1_0.txt)
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<section id="date_time.local_time.local_time_period">
  <title>Local Time Period</title>

  <link linkend="local_time_period_intro">Introduction</link> --
  <link linkend="local_time_period_header">Header</link> --
  <link linkend="local_time_period_constr">Construction</link> --
  <link linkend="local_time_period_accessors">Accessors</link> --
  <link linkend="local_time_period_operators">Operators</link>

  <anchor id="local_time_period_intro" />
  <bridgehead renderas="sect3">Introduction</bridgehead>
  <para>
    The class <code>boost::local_time::local_time_period</code> provides direct representation for ranges between two local times. Periods provide the ability to simplify some types of calculations by simplifying the conditional logic of the program. 
  </para>
  <para>
    A period that is created with beginning and end points being equal, or with a duration of zero, is known as a zero length period. Zero length periods are considered invalid (it is perfectly legal to construct an invalid period). For these periods, the <code>last</code> point will always be one unit less that the <code>begin</code> point.
  </para>

  <anchor id="local_time_period_header" />
  <bridgehead renderas="sect3">Header</bridgehead>
  <para>
    <programlisting>#include "boost/date_time/local_time/local_time.hpp" //include all types plus i/o
or
#include "boost/date_time/local_time/local_time_types.hpp" //no i/o just types</programlisting>
  </para>

  <anchor id="local_time_period_constr" />
  <bridgehead renderas="sect3">Construction</bridgehead>
  <para>
    <informaltable frame="all">
      <tgroup cols="2">
	<thead>
	  <row>
	    <entry valign="top" morerows="1">Syntax</entry>
	    <entry>Description</entry>
	  </row>
	  <row>
	    <entry>Example</entry>
	  </row>
	</thead>
	<tbody>
          <row>
            <entry valign="top" morerows="1"><screen>local_time_period(...)
  Parameters:
    local_date_time beginning
    local_date_time end</screen></entry>
	    <entry> Create a period as [begin, end). If end is &lt;= begin then the period will be defined as invalid.</entry>
	  </row>
	  <row>
            <entry><screen>time_zone_ptr 
  zone(new posix_time_zone("MST-07"));
local_date_time 
  beg(ptime(date(2005,Jan,1),hours(0)), zone);
local_date_time 
  end(ptime(date(2005,Feb,1),hours(0)), zone);
// period for the entire month of Jan 2005
local_time_period ltp(beg, end);</screen>
	    </entry>
          </row>

	  <row>
            <entry valign="top" morerows="1"><screen>local_time_period(...)
  Parameters:
    local_date_time beginning
    time_duration length</screen></entry>
	    <entry>Create a period as [begin, begin+len) where end would be begin+len. If len is &lt;= zero then the period will be defined as invalid.</entry>
	  </row>
	  <row>
            <entry><screen>time_zone_ptr 
  zone(new posix_time_zone("MST-07"));
local_date_time 
  beg(ptime(date(2005,Jan,1),hours(0)), zone);
// period for the whole day of 2005-Jan-01
local_time_period ltp(beg, hours(24));</screen>
	    </entry>
          </row>
          
          <row>
	    <entry valign="top" morerows="1"><screen>local_time_period(local_time_period rhs)</screen></entry>
	    <entry>Copy constructor</entry>
	  </row>
	  <row>
	    <entry><screen>local_time_period ltp1(ltp);</screen></entry>
	  </row>
	</tbody>
      </tgroup>
    </informaltable>
  </para>


  <anchor id="local_time_period_accessors" />
  <bridgehead renderas="sect3">Accessors</bridgehead>
  <para>
    <informaltable frame="all">
      <tgroup cols="2">
	<thead>
	  <row>
	    <entry valign="top" morerows="1">Syntax</entry>
	    <entry>Description</entry>
	  </row>
	  <row>
	    <entry>Example</entry>
	  </row>
	</thead>
	<tbody>
          <row>
	    <entry valign="top" morerows="1"><screen>local_date_time begin()</screen></entry>
	    <entry>Return first local_date_time of the period.</entry>
	  </row>
	  <row>
            <entry><screen>time_zone_ptr 
  zone(new posix_time_zone("MST-07"));
local_date_time 
  ldt((ptime(date(2005,Jan,1)),hours(0)), zone);
local_time_period ltp(ldt, hours(2));
ltp.begin(); // => 2005-Jan-01 00:00:00</screen>
	    </entry>
          </row>

	  <row>
	    <entry valign="top" morerows="1"><screen>local_date_time last()</screen></entry>
	    <entry>Return last local_date_time in the period</entry>
	  </row>
	  <row>
            <entry><screen>time_zone_ptr 
  zone(new posix_time_zone("MST-07"));
local_date_time 
  ldt((ptime(date(2005,Jan,1),hours(0))), zone);
local_time_period ltp(ldt, hours(2));
ltp.last(); // => 2005-Jan-01 01:59:59.999999999</screen>
	    </entry>
          </row>
          
	  <row>
	    <entry valign="top" morerows="1"><screen>local_date_time end()</screen></entry>
	    <entry>Return one past the last in period</entry>
	  </row>
	  <row>
            <entry><screen>time_zone_ptr 
  zone(new posix_time_zone("MST-07"));
local_date_time 
  ldt((ptime(date(2005,Jan,1),hours(0))), zone);
local_time_period ltp(ldt, hours(2));
ltp.end(); // => 2005-Jan-01 02:00:00</screen>
	    </entry>
          </row>
          
	  <row>
	    <entry valign="top" morerows="1"><screen>time_duration length()</screen></entry>
	    <entry>Return the length of the local_time period.</entry>
	  </row>
	  <row>
            <entry><screen>time_zone_ptr 
  zone(new posix_time_zone("MST-07"));
local_date_time 
  ldt((ptime(date(2005,Jan,1),hours(0))), zone);
local_time_period ltp(ldt, hours(2));
ltp.length(); // => 02:00:00</screen>
	    </entry>
          </row>
          
	  <row>
	    <entry valign="top" morerows="1"><screen>bool is_null()</screen></entry>
	    <entry>True if period is not well formed. eg: end less than or equal to begin.</entry>
	  </row>
	  <row>
            <entry><screen>time_zone_ptr 
  zone(new posix_time_zone("MST-07"));
local_date_time 
  beg((ptime(date(2005,Feb,1),hours(0))), zone);
local_date_time 
  end((ptime(date(2005,Jan,1),hours(0))), zone);
local_time_period ltp(beg, end);
ltp.is_null(); // => true</screen>
	    </entry>
          </row>
          
	  <row>
	    <entry valign="top" morerows="1"><screen>bool contains(local_date_time)</screen></entry>
	    <entry>True if local_date_time is within the period. Zero length periods cannot contain any points</entry>
	  </row>
	  <row>
            <entry><screen>time_zone_ptr 
  zone(new posix_time_zone("MST-07"));
local_date_time 
  beg((ptime(date(2005,Jan,1),hours(0))), zone);
local_date_time 
  end((ptime(date(2005,Feb,1),hours(0))), zone);
local_time_period jan_mst(beg, end);

local_date_time 
ldt((ptime(date(2005,Jan,15),hours(12))), zone);
jan_mst.contains(ldt); // => true

local_time_period zero(beg, beg);
zero.contains(beg); // false</screen></entry>
          </row>
          
	  <row>
	    <entry valign="top" morerows="1"><screen>bool contains(local_time_period)</screen></entry>
	    <entry>True if period is within the period</entry>
	  </row>
	  <row>
            <entry><screen>// using jan_mst period from previous example

local_date_time 
  beg((ptime(date(2005,Jan,7),hours(0))), zone);
local_time_period ltp(beg, hours(24));

jan_mst.contains(ltp); // => true</screen></entry>
          </row>
          
	  <row>
	    <entry valign="top" morerows="1"><screen>bool intersects(local_time_period)</screen></entry>
	    <entry> True if periods overlap</entry>
	  </row>
	  <row>
            <entry><screen>// using jan_mst period from previous example

local_date_time 
  beg((ptime(date(2005,Jan,7),hours(0))), zone);
local_date_time 
  end((ptime(date(2005,Feb,7),hours(0))), zone);
local_time_period ltp(beg, end);

jan_mst.intersects(ltp); // => true</screen></entry>
          </row>
          
	  <row>
	    <entry valign="top" morerows="1"><screen>local_time_period intersection(local_time_period)</screen></entry>
	    <entry>Calculate the intersection of 2 periods. Null if no intersection.</entry>
	  </row>
	  <row>
            <entry><screen>// using jan_mst period from previous example

local_date_time 
  beg((ptime(date(2005,Jan,7),hours(0))), zone);
local_date_time 
  end((ptime(date(2005,Feb,7),hours(0))), zone);
local_time_period ltp(beg, end);

local_time_period res(jan_mst.intersection(ltp));
// res => 2005-Jan-07 00:00:00 through
// 2005-Jan-31 23:59:59.999999999 (inclusive)</screen></entry>
          </row>
          
	  <row>
	    <entry valign="top" morerows="1"><screen>local_time_period merge(local_time_period)</screen></entry>
	    <entry>Returns union of two periods. Null if no intersection.</entry>
	  </row>
	  <row>
            <entry><screen>// using jan_mst period from previous example

local_date_time 
  beg((ptime(date(2005,Jan,7),hours(0))), zone);
local_date_time 
  end((ptime(date(2005,Feb,7),hours(0))), zone);
local_time_period ltp(beg, end);

local_time_period res(jan_mst.merge(ltp));
// res => 2005-Jan-07 00:00:00 through
// 2005-Feb-06 23:59:59.999999999 (inclusive)</screen></entry>
          </row>
          
	  <row>
	    <entry valign="top" morerows="1"><screen>local_time_period span(local_time_period)</screen></entry>
	    <entry>Combines two periods and any gap between them such that begin = min(p1.begin, p2.begin) and end = max(p1.end , p2.end).</entry>
	  </row>
	  <row>
            <entry><screen>// using jan_mst period from previous example

local_date_time 
  beg((ptime(date(2005,Mar,1),hours(0))), zone);
local_date_time 
  end((ptime(date(2005,Apr,1),hours(0))), zone);
local_time_period mar_mst(beg, end);

local_time_period res(jan_mst.span(mar_mst));
// res => 2005-Jan-01 00:00:00 through
// 2005-Mar-31 23:59:59.999999999 (inclusive)</screen></entry>
          </row>
          
          <row>
	    <entry valign="top" morerows="1"><screen>void shift(time_duration)</screen></entry>
	    <entry>Add duration to both begin and end.</entry>
	  </row>
	  <row>
            <entry><screen>local_date_time 
  beg((ptime(date(2005,Mar,1),hours(0))), zone);
local_date_time 
  end((ptime(date(2005,Apr,1),hours(0))), zone);
local_time_period mar_mst(beg, end);

mar_mst.shift(hours(48));
// mar_mst => 2005-Mar-03 00:00:00 through
// 2005-Apr-02 23:59:59.999999999 (inclusive)</screen></entry>
	  </row>
	</tbody>
      </tgroup>
    </informaltable>
  </para>


  <anchor id="local_time_period_operators" />
  <bridgehead renderas="sect3">Operators</bridgehead>
  <para>
    <informaltable frame="all">
      <tgroup cols="2">
	<thead>
	  <row>
	    <entry valign="top" morerows="1">Syntax</entry>
	    <entry>Description</entry>
	  </row>
	  <row>
	    <entry>Example</entry>
	  </row>
	</thead>
        <tbody>
          <!-- TODO: the streaming operators have not bee changed from time_period to local_time_period
          <row>
	    <entry valign="top" morerows="1"><screen>operator&lt;&lt;</screen></entry>
            <entry>Output streaming operator for time duration. Uses facet to output [date time_of_day/date time_of_day]. The default is format is <code>[YYYY-mmm-DD hh:mm:ss.fffffffff/YYYY-mmm-DD hh:mm:ss.fffffffff]</code> string where <code>mmm</code> is 3 char month name and the fractional seconds are only included if non-zero.</entry>
	  </row>
	  <row>
            <entry><screen>[2002-Jan-01 01:25:10.000000001/ \
    2002-Jan-31 01:25:10.123456789]</screen></entry>
          </row>

	  <row>
	    <entry valign="top" morerows="1"><screen>operator&gt;&gt;</screen></entry>
            <entry>Input streaming operator for time duration. Uses facet to read [date time_of_day/date time_of_day]. The default is format is <code>[YYYY-mmm-DD hh:mm:ss.fffffffff/YYYY-mmm-DD hh:mm:ss.fffffffff]</code> string where <code>mmm</code> is 3 char month name and the fractional seconds are only included if non-zero.</entry>
	  </row>
	  <row>
            <entry><screen>[2002-Jan-01 01:25:10.000000001/ \
    2002-Jan-31 01:25:10.123456789]</screen></entry>
          </row>
          -->
	  <row>
	    <entry valign="top" morerows="1"><screen>operator==, operator!=</screen></entry>
	    <entry>Equality operators. Periods are equal if ltp1.begin == ltp2.begin &amp;&amp; ltp1.last == ltp2.last</entry>
	  </row>
	  <row>
	    <entry><screen>if (ltp1 == ltp2) {...</screen></entry>
          </row>
          
	  <row>
	    <entry valign="top" morerows="1"><screen>operator&lt;</screen></entry>
	    <entry>Ordering with no overlap. True if ltp1.end() less than ltp2.begin()</entry>
	  </row>
	  <row>
	    <entry><screen>if (ltp1 &lt; ltp2) {...</screen></entry>
          </row>
          
	  <row>
	    <entry valign="top" morerows="1"><screen>operator&gt;</screen></entry>
	    <entry>Ordering with no overlap. True if ltp1.begin() greater than ltp2.end()</entry>
	  </row>
	  <row>
	    <entry><screen>if (ltp1 > ltp2) {... etc</screen></entry>
          </row>
          
          <row>
	    <entry valign="top" morerows="1"><screen>operator&lt;=, operator&gt;=</screen></entry>
	    <entry>Defined in terms of the other operators.</entry>
	  </row>
	  <row>
	    <entry></entry>
	  </row>
	</tbody>
      </tgroup>
    </informaltable>
  </para>

</section>
