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| <H1 CLASS="title">Peekable</H1> |
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| <H2>Description</H2> |
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| A Peekable <A HREF="device.html">Device</A> allows a character read from the input sequence to be putback. |
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| 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. |
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| <H2>Refinement of</H2> |
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| <A HREF="source.html">Source</A>. |
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| <H2>Associated Types</H2> |
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| Same as <A HREF="source.html">Source</A>. |
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| <H2>Notation</H2> |
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| <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> |
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| <TR><TH>Expression</TH><TH>Expression Type</TH><TH>Precondition</TH><TH>Semantics</TH><TH>Postcondition</TH></TR> |
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| <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> |
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| 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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| Attempts to put back <CODE>c</CODE> to <CODE>p</CODE>, returning <CODE>true</CODE> for success |
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| 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> |
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| Errors which occur during the execution of <A CLASS="code" HREF="../functions/putback.html"><CODE>putback</CODE></A> are be indicated by throwing exceptions. |
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| <H2>Models</H2> |
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| <LI>Standard input streams and stream buffers. |
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| <P CLASS="copyright">Revised 02 Feb 2008</P> |
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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="http://www.coderage.com/turkanis/" target="_top">Jonathan Turkanis</a></P> |
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| 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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