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| <H2>43.3 Error Indication by Stream Iterators</H2> |
| <A NAME="idx978"><!></A> |
| <P>The <B><I><A HREF="../stdlibref/basic-istream.html">istream</A></I></B> and <B><I><A HREF="../stdlibref/basic-ostream.html">ostream</A></I></B> iterators by themselves have no means of indicating the success or failure of an operation. The stream being operated on should be probed for<SAMP> good()</SAMP>, <SAMP>eof()</SAMP>, <SAMP>fail()</SAMP>, or <SAMP>bad()</SAMP> conditions. This is convenient, as stream state can be checked for exception conditions that were set in <B><I><A HREF="../stdlibref/basic-ios.html">basic_ios</A></I></B> (using the member function <SAMP>exceptions(iostate)</SAMP>) after each input or output operation.</P> |
| |
| <UL><PRE> |
| void print() |
| { |
| std::ostream_iterator<int, char, char_traits<char> > os(cout); |
| |
| try { |
| std::cout.exceptions (std::ios::failbit | std::ios::badbit); |
| *os = 3; //output `3' |
| os++; // receive next output |
| } |
| catch(std::ios_base::failure& emsg) { |
| std::cerr<<emsg.what(); |
| } |
| } |
| </PRE></UL> |
| <P>Since stream buffers do not retain information about the success or failure of operations, <B><I><A HREF="../stdlibref/basic-streambuf.html">streambuf</A></I></B> iterators provide a member function, <SAMP>failed()</SAMP>, to indicate success or failure in a preceding operation on the stream buffer. </P> |
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