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- <TITLE>Peekable</TITLE>
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- <H1 CLASS="title">Peekable</H1>
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- <H2>Description</H2>
- <P>
- A Peekable <A HREF="device.html">Device</A> allows a character read from the input sequence to be putback.
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- <P>
- The name of the concept is based on the observation that a PeekableDevice allow the user to peek at the first character in the sequence it controls by calling <A HREF="../functions/get.html"><CODE>get</CODE></A> or <A HREF="../functions/read.html"><CODE>read</CODE></A> followed by <A HREF="../functions/putback.html"><CODE>putback</CODE></A>. The names Putbackable and InputRevertable were considered but rejected.
- </P>
- <H2>Refinement of</H2>
- <A HREF="source.html">Source</A>.
- <A NAME="types"></A>
- <H2>Associated Types</H2>
- Same as <A HREF="source.html">Source</A>.
- <H2>Notation</H2>
- <TABLE CELLPADDING="2">
- <TR><TD><CODE>P</CODE></TD><TD>-</TD><TD>A type which is a model of Peekable</TD></TR>
- <TR><TD><CODE>p</CODE></TD><TD>-</TD><TD>Object of type <CODE>P</CODE></TD></TR>
- <TR><TD><CODE>c</CODE></TD><TD>-</TD><TD>Object of type equal to the character type of <CODE>P</CODE></TD></TR>
- <TR><TD><CODE>io</CODE></TD><TD>-</TD><TD>Alias for namespace <CODE>boost::iostreams</CODE></TD></TR>
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- <H2>Valid Expressions / Semantics</H2>
- <TABLE CELLPADDING="5" BORDER="1">
- <TR><TH>Expression</TH><TH>Expression Type</TH><TH>Precondition</TH><TH>Semantics</TH><TH>Postcondition</TH></TR>
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- <TD>
- <PRE CLASS="plain_code"><CODE><A HREF="../functions/putback.html">io::putback</A>(p, c)</CODE></PRE>
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- <TD><CODE>bool</CODE></TD>
- <TD>
- One or more characters has been read from <CODE>p</CODE> using <A HREF="../functions/get.html"><CODE>io::get</CODE></A> or <A HREF="../functions/read.html"><CODE>io::read</CODE></A>, with no intervening i/o operations having been performed
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- <TD>
- Attempts to put back <CODE>c</CODE> to <CODE>p</CODE>, returning <CODE>true</CODE> for success
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- <TD>
- If putback returns <CODE>true</CODE>, the next character read from <CODE>p</CODE> using <A HREF="../functions/get.html"><CODE>io::get</CODE></A> or <A HREF="../functions/read.html"><CODE>io::read</CODE></A> will be equal to <CODE>c</CODE></A>
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- <H2>Exceptions</H2>
- <P>
- Errors which occur during the execution of <A CLASS="code" HREF="../functions/putback.html"><CODE>putback</CODE></A> are be indicated by throwing exceptions.
- </P>
- <H2>Models</H2>
- <UL>
- <LI>Standard input streams and stream buffers.
- </UL>
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- <P CLASS="copyright">© Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a><br/>© Copyright 2004-2007 <a href="https://www.boost.org/users/people/jonathan_turkanis.html" target="_top">Jonathan Turkanis</a></P>
- <P CLASS="copyright">
- Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at <A HREF="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>)
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