153 lines
5.0 KiB
XML
153 lines
5.0 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
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"../../../tools/boostbook/dtd/boostbook.dtd">
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<!-- Copyright (c) 2001-2005 CrystalClear Software, Inc.
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Subject to the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
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-->
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<section id="date_time.posix_time.time_iterators">
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<title>Time Iterators</title>
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<link linkend="time_iter_intro">Introduction</link> --
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<link linkend="time_iter_header">Header</link> --
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<link linkend="time_iter_overview">Overview</link> --
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<link linkend="time_iter_operators">Operators</link>
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<anchor id="time_iter_intro" />
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<bridgehead renderas="sect3">Introduction</bridgehead>
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<para>
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Time iterators provide a mechanism for iteration through times. Time iterators are similar to <ulink url="http://www.sgi.com/tech/stl/BidirectionalIterator.html">Bidirectional Iterators</ulink>. However, time_iterators are different than standard iterators in that there is no underlying sequence, just a calculation function. In addition, time_iterators are directly comparable against instances of <link linkend="date_time.posix_time.ptime_class">class ptime</link>. Thus a second iterator for the end point of the iteration is not required, but rather a point in time can be used directly. For example, the following code iterates using a 15 minute iteration interval. The <link linkend="date_time.examples.print_hours">print hours</link> example also illustrates the use of the time_iterator.
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</para>
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<para>
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<programlisting>
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<![CDATA[
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#include "boost/date_time/posix_time/posix_time.hpp"
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#include <iostream>
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int
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main()
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{
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using namespace boost::gregorian;
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using namespace boost::posix_time;
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date d(2000,Jan,20);
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ptime start(d);
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ptime end = start + hours(1);
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time_iterator titr(start,minutes(15)); //increment by 15 minutes
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//produces 00:00:00, 00:15:00, 00:30:00, 00:45:00
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while (titr < end) {
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std::cout << to_simple_string(*titr) << std::endl;
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++titr;
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}
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std::cout << "Now backward" << std::endl;
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//produces 01:00:00, 00:45:00, 00:30:00, 00:15:00
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while (titr > start) {
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std::cout << to_simple_string(*titr) << std::endl;
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--titr;
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}
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}
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]]>
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</programlisting>
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</para>
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<anchor id="time_iter_header" />
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<bridgehead renderas="sect3">Header</bridgehead>
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<para>
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<programlisting>#include "boost/date_time/posix_time/posix_time.hpp" //include all types plus i/o
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or
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#include "boost/date_time/posix_time/posix_time_types.hpp" //no i/o just types</programlisting>
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</para>
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<anchor id="time_iter_overview" />
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<bridgehead renderas="sect3">Overview</bridgehead>
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<para>
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<informaltable frame="all">
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<tgroup cols="2">
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<thead>
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<row>
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<entry valign="top" morerows="1">Class</entry>
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<entry>Description</entry>
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</row>
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<row>
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<entry>Construction Parameters</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry valign="top" morerows="1"><screen>time_iterator</screen></entry>
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<entry>Iterate incrementing by the specified duration.</entry>
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</row>
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<row>
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<entry><screen>ptime start_time, time_duration increment</screen></entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</para>
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<anchor id="time_iter_operators" />
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<bridgehead renderas="sect3">Operators</bridgehead>
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<para>
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<informaltable frame="all">
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<tgroup cols="2">
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<thead>
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<row>
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<entry valign="top" morerows="1">Syntax</entry>
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<entry>Description</entry>
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</row>
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<row>
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<entry>Example</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry valign="top" morerows="1"><screen>operator==(const ptime& rhs),
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operator!=(const ptime& rhs),
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operator>, operator<,
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operator>=, operator<=</screen>
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</entry>
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<entry>A full complement of comparison operators</entry>
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</row>
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<row>
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<entry><screen>date d(2002,Jan,1);
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ptime start_time(d, hours(1));
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//increment by 10 minutes
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time_iterator titr(start_time, minutes(10));
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ptime end_time = start_time + hours(2);
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if (titr == end_time) // false
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if (titr != end_time) // true
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if (titr >= end_time) // false
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if (titr <= end_time) // true</screen>
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</entry>
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</row>
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<row>
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<entry valign="top" morerows="1"><screen>prefix increment</screen></entry>
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<entry>Increment the iterator by the specified duration.</entry>
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</row>
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<row>
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<entry><screen>//increment by 10 milli seconds
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time_iterator titr(start_time, milliseconds(10));
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++titr; // == start_time + 10 milliseconds</screen>
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</entry>
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</row>
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<row>
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<entry valign="top" morerows="1"><screen>prefix decrement</screen></entry>
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<entry>Decrement the iterator by the specified time duration.</entry>
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</row>
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<row>
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<entry><screen>time_duration td(1,2,3);
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time_iterator titr(start_time, td);
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--titr; // == start_time - 01:02:03</screen></entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</para>
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</section>
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