<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Tiers</title> <link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.75.2"> <link rel="home" href="../../../../index.html" title="Chapter 1. Fusion 2.0"> <link rel="up" href="../functions.html" title="Functions"> <link rel="prev" href="make_map.html" title="make_map"> <link rel="next" href="list_tie.html" title="list_tie"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td> <td align="center"><a href="../../../../../../../../index.html">Home</a></td> <td align="center"><a href="../../../../../../../../libs/libraries.htm">Libraries</a></td> <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> <td align="center"><a href="../../../../../../../../more/index.htm">More</a></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="make_map.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../functions.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="list_tie.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> </div> <div class="section"> <div class="titlepage"><div><div><h5 class="title"> <a name="fusion.container.generation.functions.tiers"></a><a class="link" href="tiers.html" title="Tiers">Tiers</a> </h5></div></div></div> <p> Tiers are sequences, where all elements are non-const reference types. They are constructed with a call to a couple of <span class="emphasis"><em>tie</em></span> function templates. The succeeding sections document the various <span class="emphasis"><em>tier</em></span> flavors. </p> <div class="itemizedlist"><ul class="itemizedlist" type="disc"> <li class="listitem"> <a class="link" href="list_tie.html" title="list_tie"><code class="computeroutput"><span class="identifier">list_tie</span></code></a> </li> <li class="listitem"> <a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">vector_tie</span></code></a> </li> <li class="listitem"> <a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">map_tie</span></code></a> </li> </ul></div> <p> Example: </p> <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">i</span><span class="special">;</span> <span class="keyword">char</span> <span class="identifier">c</span><span class="special">;</span> <span class="keyword">double</span> <span class="identifier">d</span><span class="special">;</span> <span class="special">...</span> <a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">vector_tie</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">,</span> <span class="identifier">c</span><span class="special">,</span> <span class="identifier">a</span><span class="special">);</span> </pre> <p> The <a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">vector_tie</span></code></a> function creates a <a class="link" href="../../vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a> of type <code class="computeroutput"><a class="link" href="../../vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a><span class="special"><</span><span class="keyword">int</span><span class="special">&,</span> <span class="keyword">char</span><span class="special">&,</span> <span class="keyword">double</span><span class="special">&></span></code>. The same result could be achieved with the call <a class="link" href="make_vector.html" title="make_vector"><code class="computeroutput"><span class="identifier">make_vector</span></code></a>(<a href="http://www.boost.org/doc/html/ref.html" target="_top"><code class="computeroutput"><span class="identifier">ref</span></code></a>(i), <a href="http://www.boost.org/doc/html/ref.html" target="_top"><code class="computeroutput"><span class="identifier">ref</span></code></a>(c), <a href="http://www.boost.org/doc/html/ref.html" target="_top"><code class="computeroutput"><span class="identifier">ref</span></code></a>(a)) <sup>[<a name="id964484" href="#ftn.id964484" class="footnote">9</a>]</sup>. </p> <p> A <span class="emphasis"><em>tie</em></span> can be used to 'unpack' another tuple into variables. E.g.: </p> <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">i</span><span class="special">;</span> <span class="keyword">char</span> <span class="identifier">c</span><span class="special">;</span> <span class="keyword">double</span> <span class="identifier">d</span><span class="special">;</span> <a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">vector_tie</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">,</span> <span class="identifier">c</span><span class="special">,</span> <span class="identifier">d</span><span class="special">)</span> <span class="special">=</span> <a class="link" href="make_vector.html" title="make_vector"><code class="computeroutput"><span class="identifier">make_vector</span></code></a><span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="char">'a'</span><span class="special">,</span> <span class="number">5.5</span><span class="special">);</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">i</span> <span class="special"><<</span> <span class="string">" "</span> <span class="special"><<</span> <span class="identifier">c</span> <span class="special"><<</span> <span class="string">" "</span> <span class="special"><<</span> <span class="identifier">d</span><span class="special">;</span> </pre> <p> This code prints 1 a 5.5 to the standard output stream. A sequence unpacking operation like this is found for example in ML and Python. It is convenient when calling functions which return sequences. </p> <a name="fusion.container.generation.functions.tiers.ignore"></a><h6> <a name="id964704"></a> <a class="link" href="tiers.html#fusion.container.generation.functions.tiers.ignore">Ignore</a> </h6> <p> There is also an object called <span class="emphasis"><em>ignore</em></span> which allows you to ignore an element assigned by a sequence. The idea is that a function may return a sequence, only part of which you are interested in. For example: </p> <pre class="programlisting"><span class="keyword">char</span> <span class="identifier">c</span><span class="special">;</span> <a class="link" href="vector_tie.html" title="vector_tie"><code class="computeroutput"><span class="identifier">vector_tie</span></code></a><span class="special">(</span><span class="identifier">ignore</span><span class="special">,</span> <span class="identifier">c</span><span class="special">)</span> <span class="special">=</span> <a class="link" href="make_vector.html" title="make_vector"><code class="computeroutput"><span class="identifier">make_vector</span></code></a><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="char">'a'</span><span class="special">);</span> </pre> <div class="footnotes"> <br><hr width="100" align="left"> <div class="footnote"><p><sup>[<a name="ftn.id964484" href="#id964484" class="para">9</a>] </sup> see <a href="http://www.boost.org/doc/html/ref.html" target="_top">Boost.Ref</a> for details about <code class="computeroutput"><span class="identifier">ref</span></code> </p></div> </div> </div> <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> <td align="left"></td> <td align="right"><div class="copyright-footer">Copyright © 2001-2007 Joel de Guzman, Dan Marsden, Tobias Schwinger<p> 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" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) </p> </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="make_map.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../functions.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="list_tie.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>