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| <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="id925802" href="#ftn.id925802" 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="id926022"></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.id925802" href="#id925802" 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> |
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| <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>) |
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