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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Tiers</title>
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<link rel="start" href="../../../../index.html" title="Chapter<65>1.<2E>Fusion 2.0">
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<link rel="up" href="../functions.html" title="Functions">
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<table cellpadding="2" width="100%"><tr>
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<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td>
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<td align="center"><a href="../../../../../../../../index.htm">Home</a></td>
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<a accesskey="p" href="make_map.html"><img src="../../../../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../functions.html"><img src="../../../../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="list_tie.html"><img src="../../../../../../../../doc/html/images/next.png" alt="Next"></a>
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<div class="section" lang="en">
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<div class="titlepage"><div><div><h5 class="title">
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<a name="fusion.container.generation.functions.tiers"></a><a href="tiers.html" title="Tiers">Tiers</a></h5></div></div></div>
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<p>
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Tiers are sequences, where all elements are non-const reference types.
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They are constructed with a call to a couple of <span class="emphasis"><em>tie</em></span>
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function templates. The succeeding sections document the various <span class="emphasis"><em>tier</em></span>
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flavors.
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</p>
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<div class="itemizedlist"><ul type="disc">
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<li><a href="list_tie.html" title="list_tie"><tt class="computeroutput"><span class="identifier">list_tie</span></tt></a></li>
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<li><a href="vector_tie.html" title="vector_tie"><tt class="computeroutput"><span class="identifier">vector_tie</span></tt></a></li>
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<li><a href="vector_tie.html" title="vector_tie"><tt class="computeroutput"><span class="identifier">map_tie</span></tt></a></li>
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</ul></div>
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<p>
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Example:
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</p>
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<pre class="programlisting">
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<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>
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<span class="special">...</span>
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<a href="vector_tie.html" title="vector_tie"><tt class="computeroutput"><span class="identifier">vector_tie</span></tt></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>
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</pre>
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<p>
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The <a href="vector_tie.html" title="vector_tie"><tt class="computeroutput"><span class="identifier">vector_tie</span></tt></a> function creates
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a <a href="../../vector.html" title="vector"><tt class="computeroutput"><span class="identifier">vector</span></tt></a>
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of type <tt class="computeroutput"><a href="../../vector.html" title="vector"><tt class="computeroutput"><span class="identifier">vector</span></tt></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></tt>. The same result could be achieved
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with the call <a href="make_vector.html" title="make_vector"><tt class="computeroutput"><span class="identifier">make_vector</span></tt></a>(<a href="http://www.boost.org/doc/html/ref.html" target="_top"><tt class="computeroutput"><span class="identifier">ref</span></tt></a>(i), <a href="http://www.boost.org/doc/html/ref.html" target="_top"><tt class="computeroutput"><span class="identifier">ref</span></tt></a>(c), <a href="http://www.boost.org/doc/html/ref.html" target="_top"><tt class="computeroutput"><span class="identifier">ref</span></tt></a>(a))
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<sup>[<a name="id541640" href="#ftn.id541640">10</a>]</sup>
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.
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</p>
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<p>
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A <span class="emphasis"><em>tie</em></span> can be used to 'unpack' another tuple into
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variables. E.g.:
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</p>
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<pre class="programlisting">
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<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>
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<a href="vector_tie.html" title="vector_tie"><tt class="computeroutput"><span class="identifier">vector_tie</span></tt></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 href="make_vector.html" title="make_vector"><tt class="computeroutput"><span class="identifier">make_vector</span></tt></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>
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<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>
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</pre>
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<p>
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This code prints 1 a 5.5 to the standard output stream. A sequence unpacking
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operation like this is found for example in ML and Python. It is convenient
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when calling functions which return sequences.
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</p>
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<a name="fusion.container.generation.functions.tiers.ignore"></a><h6>
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<a name="id541946"></a>
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<a href="tiers.html#fusion.container.generation.functions.tiers.ignore">Ignore</a>
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</h6>
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<p>
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There is also an object called <span class="emphasis"><em>ignore</em></span> which allows
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you to ignore an element assigned by a sequence. The idea is that a function
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may return a sequence, only part of which you are interested in. For
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example:
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</p>
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<pre class="programlisting">
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<span class="keyword">char</span> <span class="identifier">c</span><span class="special">;</span>
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<a href="vector_tie.html" title="vector_tie"><tt class="computeroutput"><span class="identifier">vector_tie</span></tt></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 href="make_vector.html" title="make_vector"><tt class="computeroutput"><span class="identifier">make_vector</span></tt></a><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="char">'a'</span><span class="special">);</span>
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</pre>
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<div class="footnotes">
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<br><hr width="100" align="left">
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<div class="footnote"><p><sup>[<a name="ftn.id541640" href="#id541640">10</a>] </sup>
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see <a href="http://www.boost.org/doc/html/ref.html" target="_top">Boost.Ref</a>
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for details about <tt class="computeroutput"><span class="identifier">ref</span></tt>
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</p></div>
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</div>
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><small>Copyright <20> 2001-2007 Joel de Guzman, Dan Marsden, Tobias
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Schwinger</small></td>
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</tr></table>
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<hr>
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<a accesskey="p" href="make_map.html"><img src="../../../../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../functions.html"><img src="../../../../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="list_tie.html"><img src="../../../../../../../../doc/html/images/next.png" alt="Next"></a>
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