| <!-- |
| Licensed to the Apache Software Foundation (ASF) under one or more |
| contributor license agreements. See the NOTICE file distributed |
| with this work for additional information regarding copyright |
| ownership. The ASF licenses this file to you under the Apache |
| License, Version 2.0 (the License); you may not use this file |
| except in compliance with the License. You may obtain a copy of |
| the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, software |
| distributed under the License is distributed on an "AS IS" BASIS, |
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or |
| implied. See the License for the specific language governing |
| permissions and limitations under the License. |
| |
| Copyright 1999-2007 Rogue Wave Software, Inc. |
| --> |
| |
| <HTML> |
| <HEAD> |
| <TITLE>istream_iterator</TITLE> |
| <LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD> |
| <BODY BGCOLOR=#FFFFFF> |
| <A HREF="istream-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="istreambuf-iterator.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>istream_iterator</H2> |
| <P><B>Library:</B> <A HREF="2-8.html">Iterators</A></P> |
| |
| <PRE><HR><B><I>istream_iterator</I></B> <IMG SRC="images/inherits.gif"> <B><I><A HREF="iterator.html">iterator</A></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">Member Types</A></LI> |
| <LI><A HREF="#sec7">Constructors</A></LI> |
| <LI><A HREF="#sec8">Operators</A></LI> |
| <LI><A HREF="#sec9">Nonmember Operators</A></LI> |
| <LI><A HREF="#sec10">Example</A></LI> |
| <LI><A HREF="#sec11">See Also</A></LI> |
| <LI><A HREF="#sec12">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="#idx717">char_type</A><BR> |
| <A HREF="#idx720">istream_iterator()</A><BR> |
| </TD> |
| <TD VALIGN=top><A HREF="#idx719">istream_type</A><BR> |
| <A HREF="#idx723">operator*()</A><BR> |
| </TD> |
| <TD VALIGN=top><A HREF="#idx725">operator++()</A><BR> |
| <A HREF="#idx724">operator->()</A><BR> |
| </TD> |
| <TD VALIGN=top><A HREF="#idx718">traits_type</A><BR> |
| </TD></TR> |
| </TABLE></UL> |
| <H4>Non-Members</H4> |
| <UL><TABLE CELLPADDING=3> |
| <TR><TD VALIGN=top> |
| <A HREF="#idx727">operator!=()</A><BR> |
| </TD> |
| <TD VALIGN=top><A HREF="#idx726">operator==()</A><BR> |
| </TD> |
| <TD VALIGN=top></TD></TR> |
| </TABLE></UL> |
| |
| <A NAME="sec2"><H3>Summary</H3></A> |
| <P>A stream iterator that has iterator capabilities for istreams. This iterator allows generic algorithms to be used directly on streams.</P> |
| <A NAME="sec3"><H3>Synopsis</H3></A> |
| |
| <PRE>#include <iterator> |
| |
| namespace std { |
| template <class T, class charT, |
| class traits = char_traits<charT>, |
| class Distance = ptrdiff_t> |
| class istream_iterator : |
| public iterator<input_iterator_tag, T, |
| Distance, const T*, const T&>; |
| } |
| </PRE> |
| <A NAME="sec4"><H3>Description</H3></A> |
| <P>Stream iterators are the standard iterator interface for input and output streams.</P> |
| <P>The class template <B><I>istream_iterator</I></B> reads elements from an input stream using <SAMP>operator >>()</SAMP>. A value of type <SAMP>T</SAMP> is retrieved and stored when the iterator is constructed and each time <SAMP>operator++()</SAMP> is called. The iterator is equal to the end-of-stream iterator value if the end-of-file is reached. You can use the constructor with no arguments to create an end-of-stream iterator. The only valid use of this iterator is to compare to other iterators when checking for end of file. Do not attempt to dereference the end-of-stream iterator; it plays the same role as the past-the-end iterator of the <SAMP>end()</SAMP> function of containers. Since an <B><I>istream_iterator</I></B> is an input iterator, you cannot assign to the value returned by dereferencing the iterator. This also means that <B><I>istream_iterators</I></B> can only be used for single pass algorithms.</P> |
| <P>Since a new value is read every time the<SAMP> operator++()</SAMP> is used on an <B><I>istream_iterator</I></B>, that operation is not equality-preserving. This means that <SAMP>i == j </SAMP>does <I>not </I>mean that <SAMP>++i == ++j</SAMP> (although two end-of-stream iterators are always equal).</P> |
| <A NAME="sec5"><H3>Interface</H3></A> |
| |
| <UL><PRE>namespace std { |
| template <class T, class charT, |
| class traits = char_traits<charT>, |
| class Distance = ptrdiff_t> |
| class istream_iterator : |
| public iterator<input_iterator_tag, T, Distance, |
| const T*, const T&> |
| { |
| |
| public: |
| typedef T value_type; |
| typedef charT char_type; |
| typedef traits traits_type; |
| typedef basic_istream<charT,traits> istream_type; |
| |
| istream_iterator(); |
| istream_iterator(istream_type&); |
| istream_iterator(const stream_iterator&); |
| |
| const T& operator*() const; |
| const T* operator->() const; |
| istream_iterator& operator++(); |
| istream_iterator operator++(int); |
| }; |
| |
| // Nonmember Operators |
| |
| template <class T, class charT, class traits,class Distance> |
| bool operator==(const istream_iterator<T,charT,traits,Distance>&, |
| const istream_iterator<T,charT,traits,Distance>&); |
| |
| template <class T, class charT, class traits,class Distance> |
| bool operator!=(const istream_iterator<T,charT,traits,Distance>&, |
| const istream_iterator<T,charT,traits,Distance>&); |
| } |
| </PRE></UL> |
| <A NAME="sec6"><H3>Member Types</H3></A> |
| |
| <A NAME="idx717"></A><PRE><B>char_type</B>; </PRE> |
| <UL> |
| <P>Type of character the stream is built on.</P> |
| </UL> |
| |
| |
| <A NAME="idx718"></A><PRE><B>traits_type</B>; </PRE> |
| <UL> |
| <P>Traits used to build the stream.</P> |
| </UL> |
| |
| |
| <A NAME="idx719"></A><PRE><B>istream_type</B>; </PRE> |
| <UL> |
| <P>Type of stream this iterator is constructed on.</P> |
| </UL> |
| |
| <A NAME="sec7"><H3>Constructors</H3></A> |
| |
| <A NAME="idx720"></A><PRE><B>istream_iterator</B>();</PRE> |
| <UL> |
| <P>Constructs an end-of-stream iterator. This iterator can be used to compare against an end-of-stream condition. Use it to provide end iterators to algorithms.</P> |
| </UL> |
| |
| |
| <A NAME="idx721"></A><PRE><B>istream_iterator</B>(istream_type& s);</PRE> |
| <UL> |
| <P>Constructs an <B><I>istream_iterator</I></B> on the given stream.</P> |
| </UL> |
| |
| |
| <A NAME="idx722"></A><PRE><B>istream_iterator</B>(const istream_iterator& x);</PRE> |
| <UL> |
| <P>Copy constructor.</P> |
| </UL> |
| |
| <A NAME="sec8"><H3>Operators</H3></A> |
| |
| <A NAME="idx723"></A><PRE>const T& |
| <B>operator*</B>() const;</PRE> |
| <UL> |
| <P>Returns the current value stored by the iterator.</P> |
| </UL> |
| |
| |
| <A NAME="idx724"></A><PRE>const T* |
| <B>operator-></B>() const;</PRE> |
| <UL> |
| <P>Returns a pointer to the current value stored by the iterator.</P> |
| </UL> |
| |
| |
| <A NAME="idx725"></A><PRE>istream_iterator& <B>operator++</B>() |
| istream_iterator <B>operator++</B>(int)</PRE> |
| <UL> |
| <P>Retrieves the next element from the input stream. </P> |
| </UL> |
| |
| <A NAME="sec9"><H3>Nonmember Operators</H3></A> |
| |
| <A NAME="idx726"></A><PRE>template <class T, class charT, class traits, class Distance> |
| bool |
| <B>operator==</B>(const istream_iterator<T,charT,traits, |
| Distance>& x, |
| const |
| istream_iterator<T,charT,traits,Distance>& y)</PRE> |
| <UL> |
| <P>Returns <SAMP>true</SAMP> if <SAMP>x</SAMP> and <SAMP>y</SAMP> both refer to the same stream or are both past-the-end.</P> |
| </UL> |
| |
| |
| <A NAME="idx727"></A><PRE>template <class T, class charT, class traits, class Distance> |
| bool |
| <B>operator!=</B>(const istream_iterator<T,charT,traits,Distance>& x, |
| const istream_iterator<T,charT,traits,Distance>& y)</PRE> |
| <UL> |
| <P>Returns <SAMP>!(x == y)</SAMP>.</P> |
| </UL> |
| |
| <A NAME="sec10"><H3>Example</H3></A> |
| |
| <UL><PRE>// |
| // io_iter.cpp |
| // |
| |
| #include <algorithm> // for copy |
| #include <iostream> // for cin, cout, endl |
| #include <iterator> // for stream_iterators, inserter |
| #include <vector> // for vector |
| #include <numeric> // for accumulate |
| |
| |
| int main () |
| { |
| // Typedefs for convenience. |
| typedef std::vector<int, std::allocator<int> > Vector; |
| |
| typedef std::istream_iterator<Vector::value_type, |
| char, std::char_traits<char>, |
| ptrdiff_t> is_iter; |
| |
| typedef std::ostream_iterator<Vector::value_type, char, |
| std::char_traits<char> > os_iter; |
| |
| Vector v; |
| |
| Vector::value_type sum = 0; |
| |
| // Collect values from cin until end of file |
| // Note use of default constructor to get ending iterator |
| std::cout << "Enter a sequence of integers (eof to quit): "; |
| std::copy (is_iter (std::cin), is_iter (), |
| std::inserter (v, v.begin ())); |
| |
| // Stream the whole vector and the sum to cout. |
| std::copy (v.begin (), v.end () -1, |
| os_iter (std::cout, " + ")); |
| |
| if (v.size ()) |
| std::cout << v.back () << " = " |
| << std::accumulate (v.begin (), v.end (), sum) |
| << std::endl; |
| |
| return 0; |
| } |
| |
| |
| Program Output: |
| </PRE></UL> |
| <UL><PRE>Enter a sequence of integers (eof to quit): 1 + 1 + 2 + 3 + 5 + |
| 8 + 13 + 21 + 45 + 66 + 111 + 177 = 453 |
| </PRE></UL> |
| <A NAME="sec11"><H3>See Also</H3></A> |
| <P><A HREF="iterators.html">Iterators</A>, <B><I><A HREF="ostream-iterator.html">ostream_iterator</A></I></B></P> |
| <A NAME="sec12"><H3>Standards Conformance</H3></A> |
| <P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 24.5.1</I></P> |
| |
| <BR> |
| <HR> |
| <A HREF="istream-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="istreambuf-iterator.html"><IMG SRC="images/bnext.gif" WIDTH=20 HEIGHT=21 ALT="Next file" BORDER=O></A> |
| |
| <!-- Google Analytics tracking code --> |
| <script src="http://www.google-analytics.com/urchin.js" type="text/javascript"> |
| </script> |
| <script type="text/javascript"> |
| _uacct = "UA-1775151-1"; |
| urchinTracker(); |
| </script> |
| <!-- end of Google Analytics tracking code --> |
| |
| </BODY> |
| </HTML> |
