php-doc-en/reference/ds/ds.deque.xml
Rudi Theunissen 845661fc07 Add docs for ds extension (not link)
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2016-07-30 10:05:36 +00:00

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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<phpdoc:classref xml:id="class.ds-deque" xmlns:phpdoc="http://php.net/ns/phpdoc" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude">
<title>Deque</title>
<titleabbrev></titleabbrev>
<partintro>
<!-- {{{ Ds\Deque intro -->
<section xml:id="ds-deque.intro">
&reftitle.intro;
<para>
A Deque (pronounced “deck”) is a sequence of values
in a contiguous buffer that grows and shrinks automatically.
The name is a common abbreviation of “double-ended queue” and is used
internally by <classname>Ds\Queue</classname>.
</para>
<para>
Two pointers are used to keep track of a head and a tail. The pointers can
“wrap around” the end of the buffer, which avoids the need to move other
values around to make room. This makes shift and unshift very fast
something a <classname>Ds\Vector</classname> cant compete with.
</para>
<para>
Accessing a value by index requires a translation between the index and its
corresponding position in the buffer: <code>((head + position) % capacity)</code>.
</para>
</section>
<!-- }}} -->
<section xml:id="ds-deque.strengths">
<title xmlns="http://docbook.org/ns/docbook">Strengths</title>
<para>
<simplelist>
<member>Supports array syntax (square brackets).</member>
<member>Uses less overall memory than an &array; for the same number of values.</member>
<member>Automatically frees allocated memory when its size drops low enough.</member>
<member>
<function>get</function>,
<function>set</function>,
<function>push</function>,
<function>pop</function>,
<function>shift</function>, and
<function>unshift</function> are all O(1).
</member>
</simplelist>
</para>
</section>
<section xml:id="ds-deque.weaknesses">
<title xmlns="http://docbook.org/ns/docbook">Weaknesses</title>
<para>
<simplelist>
<member>Capacity must be a power of 2.</member>
<member>
<function>insert</function> and
<function>remove</function> are O(n).
</member>
</simplelist>
</para>
</section>
<section xml:id="ds-deque.synopsis">
&reftitle.classsynopsis;
<!-- {{{ Synopsis -->
<classsynopsis>
<ooclass><classname>Ds\Deque</classname></ooclass>
<!-- {{{ Class synopsis -->
<classsynopsisinfo>
<ooclass>
<classname>Ds\Deque</classname>
</ooclass>
<oointerface>
<interfacename>Ds\Sequence</interfacename>
</oointerface>
</classsynopsisinfo>
<!-- }}} -->
<classsynopsisinfo role="comment">Constants</classsynopsisinfo>
<fieldsynopsis>
<modifier>const</modifier>
<type>int</type>
<varname linkend="ds-deque.constants.min-capacity">Ds\Deque::MIN_CAPACITY</varname>
<initializer>8</initializer>
</fieldsynopsis>
<classsynopsisinfo role="comment">&Methods;</classsynopsisinfo>
<xi:include xpointer="xmlns(db=http://docbook.org/ns/docbook) xpointer(id('class.ds-deque')/db:refentry/db:refsect1[@role='description']/descendant::db:methodsynopsis[not(@role='procedural')])" />
</classsynopsis>
<!-- }}} -->
</section>
<!-- {{{ Ds\Deque constants -->
<section xml:id="ds-deque.constants">
&reftitle.constants;
<variablelist>
<varlistentry xml:id="ds-deque.constants.min-capacity">
<term><constant>Ds\Deque::MIN_CAPACITY</constant></term>
<listitem>
<para></para>
</listitem>
</varlistentry>
</variablelist>
</section>
<!-- }}} -->
</partintro>
&reference.ds.ds.entities.deque;
</phpdoc:classref>
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