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 <H2>queue</H2>
 <P><B>Library:</B>&nbsp;&nbsp;<A HREF="2-7.html">Containers</A></P>

 <PRE><HR><B><I>Does not inherit</I></B><HR></PRE>

 <UL>
 <LI><A HREF="#sec1">Local Index</A></LI>
 <LI><A HREF="#sec2">Summary</A></LI>
 <LI><A HREF="#sec3">Synopsis</A></LI>
 <LI><A HREF="#sec4">Description</A></LI>
 <LI><A HREF="#sec5">Interface</A></LI>
 <LI><A HREF="#sec6">Constructors</A></LI>
 <LI><A HREF="#sec7">Member Functions</A></LI>
 <LI><A HREF="#sec8">Nonmember Operators</A></LI>
 <LI><A HREF="#sec9">Example</A></LI>
 <LI><A HREF="#sec10">See Also</A></LI>
 <LI><A HREF="#sec11">Standards Conformance</A></LI>
 </UL>
 <A NAME="sec1"><H3>Local Index</H3></A>
 <H4>Members</H4>
 <UL><TABLE CELLPADDING=3>
 <TR><TD VALIGN=top>
 <A HREF="#idx1112">back()</A><BR>
 <A HREF="#idx1114">empty()</A><BR>
 </TD>
 <TD VALIGN=top><A HREF="#idx1115">front()</A><BR>
 <A HREF="#idx1117">pop()</A><BR>
 </TD>
 <TD VALIGN=top><A HREF="#idx1118">push()</A><BR>
 <A HREF="#idx1111">queue()</A><BR>
 </TD>
 <TD VALIGN=top><A HREF="#idx1119">size()</A><BR>
 </TD></TR>
 </TABLE></UL>
 <H4>Non-Members</H4>
 <UL><TABLE CELLPADDING=3>
 <TR><TD VALIGN=top>
 <A HREF="#idx1121">operator!=()</A><BR>
 </TD>
 <TD VALIGN=top><A HREF="#idx1123">operator&gt;()</A><BR>
 </TD>
 <TD VALIGN=top><A HREF="#idx1122">operator&lt;()</A><BR>
 </TD>
 <TD VALIGN=top><A HREF="#idx1120">operator==()</A><BR>
 </TD></TR>
 </TABLE></UL>

 <A NAME="sec2"><H3>Summary</H3></A>
 <P>A container adaptor that behaves like a queue (first in, first out)</P>
 <A NAME="sec3"><H3>Synopsis</H3></A>

 <PRE>#include &lt;queue&gt;

 namespace std {
   template &lt;class T, class Container = deque&lt;T&gt; &gt;
   class queue;
 }
 </PRE>
 <A NAME="sec4"><H3>Description</H3></A>
 <P>The <B><I>queue</I></B> container adaptor lets a container act as a queue. In a queue, items are pushed into the back of the container and removed from the front. The first items pushed into the queue are the first items to be popped off of the queue (first in, first out, or FIFO). </P>
 <P><B><I>queue</I></B> can adapt any container that supports the <SAMP>front()</SAMP>, <SAMP>back()</SAMP>, <SAMP>push_back()</SAMP>, and <SAMP>pop_front()</SAMP> operations. In particular, <B><I><A HREF="deque.html">deque</A></I></B> and <B><I><A HREF="list.html">list</A></I></B> can be used. </P>
 <A NAME="sec5"><H3>Interface</H3></A>

 <UL><PRE>namespace std {

   template &lt;class T, class Container = deque&lt;T&gt; &gt;
   class queue {

     public:

       // typedefs
       typedef typename Container::value_type value_type;
       typedef typename Container::size_type size_type;
       typedef Container container_type;

       // Construct/Copy/Destroy
       explicit queue (const Container&amp; = Container());

       // Accessors
       bool empty () const;
      size_type size () const;
      value_type&amp; front ();
      const value_type&amp; front () const;
      value_type&amp; back ();
      const value_type&amp; back () const;
      void push (const value_type&amp;);
      void pop ();
   };

   // Nonmember Operators

   template &lt;class T, class Container&gt;
   bool operator==(const queue&lt;T, Container&gt;&amp;,
                   const queue&lt;T, Container&gt;&amp;);

   template &lt;class T, class Container&gt;
   bool operator!=(const queue&lt;T, Container&gt;&amp;,
                   const queue&lt;T, Container&gt;&amp;);

   template &lt;class T, class Container&gt;
   bool operator&lt;(const queue&lt;T, Container&gt;&amp;,
                  const queue&lt;T, Container&gt;&amp;);

   template &lt;class T, class Container&gt;
   bool operator&gt;(const queue&lt;T, Container&gt;&amp;,
                  const queue&lt;T, Container&gt;&amp;);

   template &lt;class T, class Container&gt;
   bool operator&lt;=(const queue&lt;T, Container&gt;&amp;,
                   const queue&lt;T, Container&gt;&amp;);

   template &lt;class T, class Container&gt;
   bool operator&gt;=(const queue&lt;T, Container&gt;&amp;,
                   const queue&lt;T, Container&gt;&amp;);
 }
 </PRE></UL>
 <A NAME="sec6"><H3>Constructors</H3></A>

 <A NAME="idx1111"></A><PRE>explicit <B>queue</B>(const Container&amp; = Container());</PRE>
 <UL>
 <P>Creates a queue of zero elements.</P>
 </UL>

 <A NAME="sec7"><H3>Member Functions</H3></A>

 <A NAME="idx1112"></A><PRE>value_type&amp;
 <B>back</B>();</PRE>
 <UL>
 <P>Returns a reference to the item at the back of the queue (the last item pushed into the queue).</P>
 </UL>


 <A NAME="idx1113"></A><PRE>const value_type&amp;
 <B>back</B>() const;</PRE>
 <UL>
 <P>Returns a constant reference to the item at the back of the queue as a <SAMP>const_value_type</SAMP>.</P>
 </UL>


 <A NAME="idx1114"></A><PRE>bool
 <B>empty</B>() const;</PRE>
 <UL>
 <P>Returns <SAMP>true</SAMP> if the queue is empty, otherwise <SAMP>false</SAMP>.</P>
 </UL>


 <A NAME="idx1115"></A><PRE>value_type&amp;
 <B>front</B>();</PRE>
 <UL>
 <P>Returns a reference to the item at the front of the queue.</P>
 </UL>


 <A NAME="idx1116"></A><PRE>const value_type&amp;
 <B>front</B>() const;</PRE>
 <UL>
 <P>Returns a constant reference to the item at the front of the queue as a <SAMP>const_value_type</SAMP>.</P>
 </UL>


 <A NAME="idx1117"></A><PRE>void
 <B>pop</B>();</PRE>
 <UL>
 <P>Removes the item at the front of the queue.</P>
 </UL>


 <A NAME="idx1118"></A><PRE>void
 <B>push</B>(const value_type&amp; x);</PRE>
 <UL>
 <P>Pushes <SAMP>x</SAMP> onto the back of the queue.</P>
 </UL>


 <A NAME="idx1119"></A><PRE>size_type
 <B>size</B>() const;</PRE>
 <UL>
 <P>Returns the number of elements on the queue.</P>
 </UL>

 <A NAME="sec8"><H3>Nonmember Operators</H3></A>

 <A NAME="idx1120"></A><PRE>template &lt;class T, class Container&gt;
   bool <B>operator==</B>(const queue&lt;T, Container&gt;&amp; x,
                    const queue&lt;T, Container&gt;&amp; y);</PRE>
 <UL>
 <P>   Returns <SAMP>true</SAMP> if <SAMP>x</SAMP> is the same as <SAMP>y</SAMP>.</P>
 </UL>


 <A NAME="idx1121"></A><PRE>template &lt;class T, class Container&gt;
   bool <B>operator!=</B>(const queue&lt;T, Container&gt;&amp; x,
                    const queue&lt;T, Container&gt;&amp; y);</PRE>
 <UL>
 <P>   Returns <SAMP>!(x==y)</SAMP>.</P>
 </UL>


 <A NAME="idx1122"></A><PRE>template &lt;class T, class Container&gt;
   bool <B>operator&lt;</B>(const queue&lt;T, Container&gt;&amp; x,
                   const queue&lt;T, Container&gt;&amp; y);</PRE>
 <UL>
 <P>Returns <SAMP>true</SAMP> if the queue defined by the elements contained in <SAMP>x</SAMP> is lexicographically less than the queue defined by the elements contained in <SAMP>y</SAMP>.</P>
 </UL>


 <A NAME="idx1123"></A><PRE>template &lt;class T, class Container&gt;
   bool <B>operator&gt;</B>(const queue&lt;T, Container&gt;&amp; x,
                   const queue&lt;T, Container&gt;&amp; y);</PRE>
 <UL>
 <P>Returns <SAMP>y &lt; x</SAMP>.</P>
 </UL>


 <A NAME="idx1124"></A><PRE>template &lt;class T, class Container&gt;
   bool <B>operator&lt;</B>(const queue&lt;T, Container&gt;&amp; x,
                   const queue&lt;T, Container&gt;&amp; y);</PRE>
 <UL>
 <P>Returns <SAMP>!(y &lt; x)</SAMP>.</P>
 </UL>


 <A NAME="idx1125"></A><PRE>template &lt;class T, class Container&gt;
   bool <B>operator&lt;</B>(const queue&lt;T, Container&gt;&amp; x,
                   const queue&lt;T, Container&gt;&amp; y);</PRE>
 <UL>
 <P>Returns <SAMP>!(x &lt; y)</SAMP>.</P>
 </UL>

 <A NAME="sec9"><H3>Example</H3></A>

 <UL><PRE>//
 //  queue.cpp
 //

 #include &lt;deque&gt;      // for deque
 #include &lt;iostream&gt;   // for cout, endl
 #include &lt;list&gt;       // for list
 #include &lt;queue&gt;      // for queue
 #include &lt;string&gt;     // for string


 int main ()
 {
     typedef std::queue&lt;int, std::list&lt;int,
                                       std::allocator&lt;int&gt; &gt; &gt;
             IQueue;

     // Make a queue using a deque container.
     IQueue q;

     // Push a couple of values on and retrieve them.
     q.push (1);
     q.push (2);

     std::cout &lt;&lt; q.front () &lt;&lt; std::endl;
     std::cout &lt;&lt; q.back () &lt;&lt; std::endl;

     typedef std::queue&lt;std::string, std::deque&lt;std::string,
                        std::allocator&lt;std::string&gt; &gt; &gt; SQueue;

     // Make a queue of strings using a deque container.
     SQueue qs;

     // Push on a few strings then pop them back off.
     for (int i = 0; i &lt; 10; i++) {
         qs.push (std::string (i + 1, 'a'));
         std::cout &lt;&lt; qs.front () &lt;&lt; std::endl;
     }

     for (int j = 0; j &lt; 10; j++) {
         std::cout &lt;&lt; qs.front () &lt;&lt; std::endl;
         qs.pop ();
     }

     // Return 0 if both containers are empty,
     // a non-zero value otherwise.
     return !(2 == q.size () &amp;&amp; qs.empty ());
 }


 Program Output:
 </PRE></UL>
 <UL><PRE>1
 2
 a
 a
 a
 a
 a
 a
 a
 a
 a
 a
 a
 aa
 aaa
 aaaa
 aaaaa
 aaaaaa
 aaaaaaa
 aaaaaaaa
 aaaaaaaaa
 aaaaaaaaaa
 </PRE></UL>
 <A NAME="sec10"><H3>See Also</H3></A>
 <P><B><I><A HREF="allocator.html">allocator</A></I></B>, <A HREF="containers.html">Containers</A>, <B><I><A HREF="priority-queue.html">priority_queue</A></I></B></P>
 <A NAME="sec11"><H3>Standards Conformance</H3></A>
 <P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 23.2.3.1</I></P>

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	<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
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	<A HREF="queue-h.html"><IMG SRC="images/bprev.gif" WIDTH=20 HEIGHT=21 ALT="Previous file" BORDER=O></A><A HREF="noframes.html"><IMG SRC="images/btop.gif" WIDTH=56 HEIGHT=21 ALT="Top of Document" BORDER=O></A><A HREF="booktoc.html"><IMG SRC="images/btoc.gif" WIDTH=56 HEIGHT=21 ALT="Contents" BORDER=O></A><A HREF="tindex.html"><IMG SRC="images/bindex.gif" WIDTH=56 HEIGHT=21 ALT="Index page" BORDER=O></A><A HREF="randomaccessiterators.html"><IMG SRC="images/bnext.gif" WIDTH=25 HEIGHT=21 ALT="Next file" BORDER=O></A><DIV CLASS="DOCUMENTNAME"><B>Apache C++ Standard Library Reference Guide</B></DIV>
	<H2>queue</H2>
	<P><B>Library:</B>  <A HREF="2-7.html">Containers</A></P>

	<PRE><HR><B><I>Does not inherit</I></B><HR></PRE>

	<UL>
	<LI><A HREF="#sec1">Local Index</A></LI>
	<LI><A HREF="#sec2">Summary</A></LI>
	<LI><A HREF="#sec3">Synopsis</A></LI>
	<LI><A HREF="#sec4">Description</A></LI>
	<LI><A HREF="#sec5">Interface</A></LI>
	<LI><A HREF="#sec6">Constructors</A></LI>
	<LI><A HREF="#sec7">Member Functions</A></LI>
	<LI><A HREF="#sec8">Nonmember Operators</A></LI>
	<LI><A HREF="#sec9">Example</A></LI>
	<LI><A HREF="#sec10">See Also</A></LI>
	<LI><A HREF="#sec11">Standards Conformance</A></LI>
	</UL>
	<A NAME="sec1"><H3>Local Index</H3></A>
	<H4>Members</H4>
	<UL><TABLE CELLPADDING=3>
	<TR><TD VALIGN=top>
	<A HREF="#idx1112">back()</A><BR>
	<A HREF="#idx1114">empty()</A><BR>
	</TD>
	<TD VALIGN=top><A HREF="#idx1115">front()</A><BR>
	<A HREF="#idx1117">pop()</A><BR>
	</TD>
	<TD VALIGN=top><A HREF="#idx1118">push()</A><BR>
	<A HREF="#idx1111">queue()</A><BR>
	</TD>
	<TD VALIGN=top><A HREF="#idx1119">size()</A><BR>
	</TD></TR>
	</TABLE></UL>
	<H4>Non-Members</H4>
	<UL><TABLE CELLPADDING=3>
	<TR><TD VALIGN=top>
	<A HREF="#idx1121">operator!=()</A><BR>
	</TD>
	<TD VALIGN=top><A HREF="#idx1123">operator>()</A><BR>
	</TD>
	<TD VALIGN=top><A HREF="#idx1122">operator<()</A><BR>
	</TD>
	<TD VALIGN=top><A HREF="#idx1120">operator==()</A><BR>
	</TD></TR>
	</TABLE></UL>

	<A NAME="sec2"><H3>Summary</H3></A>
	<P>A container adaptor that behaves like a queue (first in, first out)</P>
	<A NAME="sec3"><H3>Synopsis</H3></A>

	<PRE>#include <queue>

	namespace std {
	template <class T, class Container = deque<T> >
	class queue;
	}
	</PRE>
	<A NAME="sec4"><H3>Description</H3></A>
	<P>The <B><I>queue</I></B> container adaptor lets a container act as a queue. In a queue, items are pushed into the back of the container and removed from the front. The first items pushed into the queue are the first items to be popped off of the queue (first in, first out, or FIFO). </P>
	<P><B><I>queue</I></B> can adapt any container that supports the <SAMP>front()</SAMP>, <SAMP>back()</SAMP>, <SAMP>push_back()</SAMP>, and <SAMP>pop_front()</SAMP> operations. In particular, <B><I><A HREF="deque.html">deque</A></I></B> and <B><I><A HREF="list.html">list</A></I></B> can be used. </P>
	<A NAME="sec5"><H3>Interface</H3></A>

	<UL><PRE>namespace std {

	template <class T, class Container = deque<T> >
	class queue {

	public:

	// typedefs
	typedef typename Container::value_type value_type;
	typedef typename Container::size_type size_type;
	typedef Container container_type;

	// Construct/Copy/Destroy
	explicit queue (const Container& = Container());

	// Accessors
	bool empty () const;
	size_type size () const;
	value_type& front ();
	const value_type& front () const;
	value_type& back ();
	const value_type& back () const;
	void push (const value_type&);
	void pop ();
	};

	// Nonmember Operators

	template <class T, class Container>
	bool operator==(const queue<T, Container>&,
	const queue<T, Container>&);

	template <class T, class Container>
	bool operator!=(const queue<T, Container>&,
	const queue<T, Container>&);

	template <class T, class Container>
	bool operator<(const queue<T, Container>&,
	const queue<T, Container>&);

	template <class T, class Container>
	bool operator>(const queue<T, Container>&,
	const queue<T, Container>&);

	template <class T, class Container>
	bool operator<=(const queue<T, Container>&,
	const queue<T, Container>&);

	template <class T, class Container>
	bool operator>=(const queue<T, Container>&,
	const queue<T, Container>&);
	}
	</PRE></UL>
	<A NAME="sec6"><H3>Constructors</H3></A>

	<A NAME="idx1111"></A><PRE>explicit <B>queue</B>(const Container& = Container());</PRE>
	<UL>
	<P>Creates a queue of zero elements.</P>
	</UL>

	<A NAME="sec7"><H3>Member Functions</H3></A>

	<A NAME="idx1112"></A><PRE>value_type&
	<B>back</B>();</PRE>
	<UL>
	<P>Returns a reference to the item at the back of the queue (the last item pushed into the queue).</P>
	</UL>


	<A NAME="idx1113"></A><PRE>const value_type&
	<B>back</B>() const;</PRE>
	<UL>
	<P>Returns a constant reference to the item at the back of the queue as a <SAMP>const_value_type</SAMP>.</P>
	</UL>


	<A NAME="idx1114"></A><PRE>bool
	<B>empty</B>() const;</PRE>
	<UL>
	<P>Returns <SAMP>true</SAMP> if the queue is empty, otherwise <SAMP>false</SAMP>.</P>
	</UL>


	<A NAME="idx1115"></A><PRE>value_type&
	<B>front</B>();</PRE>
	<UL>
	<P>Returns a reference to the item at the front of the queue.</P>
	</UL>


	<A NAME="idx1116"></A><PRE>const value_type&
	<B>front</B>() const;</PRE>
	<UL>
	<P>Returns a constant reference to the item at the front of the queue as a <SAMP>const_value_type</SAMP>.</P>
	</UL>


	<A NAME="idx1117"></A><PRE>void
	<B>pop</B>();</PRE>
	<UL>
	<P>Removes the item at the front of the queue.</P>
	</UL>


	<A NAME="idx1118"></A><PRE>void
	<B>push</B>(const value_type& x);</PRE>
	<UL>
	<P>Pushes <SAMP>x</SAMP> onto the back of the queue.</P>
	</UL>


	<A NAME="idx1119"></A><PRE>size_type
	<B>size</B>() const;</PRE>
	<UL>
	<P>Returns the number of elements on the queue.</P>
	</UL>

	<A NAME="sec8"><H3>Nonmember Operators</H3></A>

	<A NAME="idx1120"></A><PRE>template <class T, class Container>
	bool <B>operator==</B>(const queue<T, Container>& x,
	const queue<T, Container>& y);</PRE>
	<UL>
	<P> Returns <SAMP>true</SAMP> if <SAMP>x</SAMP> is the same as <SAMP>y</SAMP>.</P>
	</UL>


	<A NAME="idx1121"></A><PRE>template <class T, class Container>
	bool <B>operator!=</B>(const queue<T, Container>& x,
	const queue<T, Container>& y);</PRE>
	<UL>
	<P> Returns <SAMP>!(x==y)</SAMP>.</P>
	</UL>


	<A NAME="idx1122"></A><PRE>template <class T, class Container>
	bool <B>operator<</B>(const queue<T, Container>& x,
	const queue<T, Container>& y);</PRE>
	<UL>
	<P>Returns <SAMP>true</SAMP> if the queue defined by the elements contained in <SAMP>x</SAMP> is lexicographically less than the queue defined by the elements contained in <SAMP>y</SAMP>.</P>
	</UL>


	<A NAME="idx1123"></A><PRE>template <class T, class Container>
	bool <B>operator></B>(const queue<T, Container>& x,
	const queue<T, Container>& y);</PRE>
	<UL>
	<P>Returns <SAMP>y < x</SAMP>.</P>
	</UL>


	<A NAME="idx1124"></A><PRE>template <class T, class Container>
	bool <B>operator<</B>(const queue<T, Container>& x,
	const queue<T, Container>& y);</PRE>
	<UL>
	<P>Returns <SAMP>!(y < x)</SAMP>.</P>
	</UL>


	<A NAME="idx1125"></A><PRE>template <class T, class Container>
	bool <B>operator<</B>(const queue<T, Container>& x,
	const queue<T, Container>& y);</PRE>
	<UL>
	<P>Returns <SAMP>!(x < y)</SAMP>.</P>
	</UL>

	<A NAME="sec9"><H3>Example</H3></A>

	<UL><PRE>//
	// queue.cpp
	//

	#include <deque> // for deque
	#include <iostream> // for cout, endl
	#include <list> // for list
	#include <queue> // for queue
	#include <string> // for string


	int main ()
	{
	typedef std::queue<int, std::list<int,
	std::allocator<int> > >
	IQueue;

	// Make a queue using a deque container.
	IQueue q;

	// Push a couple of values on and retrieve them.
	q.push (1);
	q.push (2);

	std::cout << q.front () << std::endl;
	std::cout << q.back () << std::endl;

	typedef std::queue<std::string, std::deque<std::string,
	std::allocator<std::string> > > SQueue;

	// Make a queue of strings using a deque container.
	SQueue qs;

	// Push on a few strings then pop them back off.
	for (int i = 0; i < 10; i++) {
	qs.push (std::string (i + 1, 'a'));
	std::cout << qs.front () << std::endl;
	}

	for (int j = 0; j < 10; j++) {
	std::cout << qs.front () << std::endl;
	qs.pop ();
	}

	// Return 0 if both containers are empty,
	// a non-zero value otherwise.
	return !(2 == q.size () && qs.empty ());
	}


	Program Output:
	</PRE></UL>
	<UL><PRE>1
	2
	a
	a
	a
	a
	a
	a
	a
	a
	a
	a
	a
	aa
	aaa
	aaaa
	aaaaa
	aaaaaa
	aaaaaaa
	aaaaaaaa
	aaaaaaaaa
	aaaaaaaaaa
	</PRE></UL>
	<A NAME="sec10"><H3>See Also</H3></A>
	<P><B><I><A HREF="allocator.html">allocator</A></I></B>, <A HREF="containers.html">Containers</A>, <B><I><A HREF="priority-queue.html">priority_queue</A></I></B></P>
	<A NAME="sec11"><H3>Standards Conformance</H3></A>
	<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 23.2.3.1</I></P>

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