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| <!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN" |
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| <!-- Copyright (c) 2001-2005 CrystalClear Software, Inc. |
| 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) |
| --> |
| |
| <section xmlns:xi="http://www.w3.org/2001/XInclude" id="date_time.gregorian.date_duration"> |
| <title>Date Duration (aka Days)</title> |
| |
| <link linkend="duration_intro">Introduction</link> -- |
| <link linkend="duration_header">Header</link> -- |
| <link linkend="duration_construction">Construction</link> -- |
| <link linkend="duration_accessors">Accessors</link> -- |
| <link linkend="duration_operators">Operators</link> -- |
| <link linkend="additional_duration_types">Additional Duration Types</link> |
| |
| <anchor id="duration_intro" /> |
| <bridgehead renderas="sect3">Introduction</bridgehead> |
| <para> |
| The class boost::gregorian::date_duration is a simple day count used for arithmetic with <link linkend="date_time.gregorian.date_class">gregorian::date</link>. A duration can be either positive or negative. |
| </para> |
| <para> |
| As of version 1_32 the date_duration class has been typedef'd as days in the boost::gregorian namespace. Throughout the examples you will find days used instead of date_duration. |
| </para> |
| |
| <anchor id="duration_header" /> |
| <bridgehead renderas="sect3">Header</bridgehead> |
| <para> |
| <programlisting>#include "boost/date_time/gregorian/gregorian.hpp" //include all types plus i/o |
| or |
| #include "boost/date_time/gregorian/gregorian_types.hpp" //no i/o just types</programlisting> |
| </para> |
| |
| <anchor id="duration_construction" /> |
| <bridgehead renderas="sect3">Construction</bridgehead> |
| <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>date_duration(long)</screen></entry> |
| <entry>Create a duration count.</entry> |
| </row> |
| <row> |
| <entry><screen>date_duration dd(3); //3 days</screen></entry> |
| </row> |
| |
| <row> |
| <entry valign="top" morerows="1"><screen>days(special_values sv)</screen></entry> |
| <entry>Constructor for infinities, not-a-date-time, max_date_time, and min_date_time</entry> |
| </row> |
| <row> |
| <entry><screen>days dd1(neg_infin); |
| days dd2(pos_infin); |
| days dd3(not_a_date_time); |
| days dd4(max_date_time); |
| days dd5(min_date_time);</screen></entry> |
| </row> |
| |
| </tbody> |
| </tgroup> |
| </informaltable> |
| |
| <anchor id="duration_accessors" /> |
| <bridgehead renderas="sect3">Accessors</bridgehead> |
| <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>long days() const</screen></entry> |
| <entry>Get the day count.</entry> |
| </row> |
| <row> |
| <entry><screen>date_duration dd(3); dd.days() --> 3</screen></entry> |
| </row> |
| |
| <row> |
| <entry valign="top" morerows="1"><screen>bool is_negative() const</screen></entry> |
| <entry>True if number of days is less than zero.</entry> |
| </row> |
| <row> |
| <entry><screen>date_duration dd(-1); dd.is_negative() --> true</screen></entry> |
| </row> |
| |
| <row> |
| <entry valign="top" morerows="1"><screen>static date_duration unit()</screen></entry> |
| <entry>Return smallest possible unit of duration type.</entry> |
| </row> |
| <row> |
| <entry><screen>date_duration::unit() --> date_duration(1)</screen></entry> |
| </row> |
| |
| <row> |
| <entry valign="top" morerows="1"><screen>bool is_special() const</screen></entry> |
| <entry>Returns true if days is any <code>special_value</code></entry> |
| </row> |
| <row> |
| <entry><screen>days dd(pos_infin); |
| days dd2(not_a_date_time); |
| days dd3(25); |
| dd.is_special(); // --> true |
| dd2.is_special(); // --> true |
| dd3.is_special(); // --> false</screen></entry> |
| </row> |
| |
| </tbody> |
| </tgroup> |
| </informaltable> |
| |
| <anchor id="duration_operators" /> |
| <bridgehead renderas="sect3">Operators</bridgehead> |
| <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>operator<<, operator>></screen></entry> |
| <entry>Streaming operators. <emphasis role="strong">Note:</emphasis> As of version 1.33, streaming operations have been greatly improved. See <link linkend="date_time.date_time_io">Date Time IO System</link> for more details (including exceptions and error conditions).</entry> |
| </row> |
| <row> |
| <entry><screen>date d(not_a_date_time); |
| stringstream ss("2002-Jan-01"); |
| ss >> d; |
| std::cout << d; // "2002-Jan-01" |
| </screen> |
| </entry> |
| </row> |
| |
| <row> |
| <entry valign="top" morerows="1"><screen>operator==, operator!=, |
| operator>, operator<, |
| operator>=, operator<=</screen> |
| </entry> |
| <entry>A full complement of comparison operators</entry> |
| </row> |
| <row> |
| <entry><screen>dd1 == dd2, etc</screen></entry> |
| </row> |
| |
| <row> |
| <entry valign="top" morerows="1"><screen>date_duration operator+(date_duration) const</screen></entry> |
| <entry>Add date durations.</entry> |
| </row> |
| <row> |
| <entry><screen>date_duration dd1(3); |
| date_duration dd2(5); |
| date_duration dd3 = dd1 + dd2;</screen> |
| </entry> |
| </row> |
| |
| <row> |
| <entry valign="top" morerows="1"><screen>date_duration operator-(date_duration) const</screen></entry> |
| <entry>Subtract durations.</entry> |
| </row> |
| <row> |
| <entry><screen>date_duration dd1(3); |
| date_duration dd2(5); |
| date_duration dd3 = dd1 - dd2;</screen> |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| |
| <anchor id="additional_duration_types" /> |
| <bridgehead renderas="sect3">Additional Duration Types</bridgehead> |
| <para>These additional types are logical representations of spans of days.</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>months(int num_of_months)</screen></entry> |
| <entry>A logical month representation. Depending on the usage, this <code>months</code> object may cover a span of 28 to 31 days. The objects also use a snap to end-of-month behavior when used in conjunction with a date that is the last day of a given month. <emphasis role="strong">WARNING: this behavior may lead to unexpected results.</emphasis> See: <link linkend="snap_to_details">Reversibility of Operations Pitfall</link> for complete details and alternatives.</entry> |
| </row> |
| <row> |
| <entry><screen>months single(1); |
| date leap_year(2004,Jan,31); |
| date norm_year(2005,Jan,31); |
| leap_year + single; // => 2004-Feb-29 |
| norm_year + single; // => 2005-Feb-28 |
| date(2005,Jan,1) + single; // => 2005-Feb-01 |
| date(2005,Feb,1) + single; // => 2005-Mar-01 |
| date(2005,Feb,28) + single; // => 2005-Mar-31</screen></entry> |
| </row> |
| |
| <row> |
| <entry valign="top" morerows="1"><screen>years(int num_of_years)</screen></entry> |
| <entry>A logical representation of a year. The <code>years</code> object has the same behavior as the <code>months</code> objects with regards to the end-of-the-month.</entry> |
| </row> |
| <row> |
| <entry><screen>years single(1); |
| date(2003,Feb,28) + single; |
| // results in => 2004-Feb-29 |
| date(2004,Feb,29) + single; |
| // results in => 2005-Feb-28</screen></entry> |
| </row> |
| |
| <row> |
| <entry valign="top" morerows="1"><screen>weeks(int num_of_weeks)</screen></entry> |
| <entry>A duration type representing a number of <code>n * 7</code> days.</entry> |
| </row> |
| <row> |
| <entry><screen>weeks single(1); |
| date(2005,Jan,1) + single; // => 2005-Jan-08</screen></entry> |
| </row> |
| |
| </tbody> |
| </tgroup> |
| </informaltable> |
| |
| <xi:include href="snap_to_details.xml"/> |
| |
| </section> |
