php-doc-en/reference/ds/ds.deque.xml

<?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>The Deque class</title>
 <titleabbrev>Deque</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> can’t 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>
     <oointerface>
      <interfacename>ArrayAccess</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)">
     <xi:fallback/>
    </xi:include>
   </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>
<!-- }}} -->

  <section role="changelog">
   &reftitle.changelog;
   <para>
    <informaltable>
     <tgroup cols="2">
      <thead>
       <row>
        <entry>&Version;</entry>
        <entry>&Description;</entry>
       </row>
      </thead>
      <tbody>
       <row>
        <entry>PECL ds 1.3.0</entry>
        <entry>
         The class now implements <classname>ArrayAccess</classname>.
        </entry>
       </row>
      </tbody>
     </tgroup>
    </informaltable>
   </para>
  </section>

 </partintro>

 &reference.ds.ds.entities.deque;

</phpdoc:classref>

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