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<title>Segmentational Fineness</title>
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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_icl.function_reference.segmentational_fineness"></a><a class="link" href="segmentational_fineness.html" title="Segmentational Fineness">Segmentational
Fineness</a>
</h3></div></div></div>
<p>
For overloading tables on infix operators, we need to break down <code class="computeroutput"><a class="link" href="../../boost/icl/interval_set.html" title="Class template interval_set">interval_sets</a></code> and <code class="computeroutput"><a class="link" href="../../boost/icl/interval_map.html" title="Class template interval_map">interval_maps</a></code>
to the specific class templates
</p>
<a name="ph_def_S1"></a><a name="ph_def_S2"></a><a name="ph_def_S3"></a><a name="ph_def_M1"></a><a name="ph_def_M3"></a><div class="informaltable"><table class="table">
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</p>
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<p>
<span class="bold"><strong>S1</strong></span>
</p>
</td>
<td>
<p>
<code class="computeroutput"><a class="link" href="../../boost/icl/interval_set.html" title="Class template interval_set">interval_set</a></code>
</p>
</td>
<td>
<p>
<span class="bold"><strong>S2</strong></span>
</p>
</td>
<td>
<p>
<code class="computeroutput"><a class="link" href="../../boost/icl/separate_interval_set.html" title="Class template separate_interval_set">separate_interval_set</a></code>
</p>
</td>
<td>
<p>
<span class="bold"><strong>S3</strong></span>
</p>
</td>
<td>
<p>
<code class="computeroutput"><a class="link" href="../../boost/icl/split_interval_set.html" title="Class template split_interval_set">split_interval_set</a></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="bold"><strong>M1</strong></span>
</p>
</td>
<td>
<p>
<code class="computeroutput"><a class="link" href="../../boost/icl/interval_map.html" title="Class template interval_map">interval_map</a></code>
</p>
</td>
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<p>
</p>
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<p>
</p>
</td>
<td>
<p>
<span class="bold"><strong>M3</strong></span>
</p>
</td>
<td>
<p>
<code class="computeroutput"><a class="link" href="../../boost/icl/split_interval_map.html" title="Class template split_interval_map">split_interval_map</a></code>
</p>
</td>
</tr>
</tbody>
</table></div>
<p>
choosing <span class="bold"><strong>Si</strong></span> and <span class="bold"><strong>Mi</strong></span>
as placeholders.
</p>
<p>
The indices <span class="bold"><strong>i</strong></span> of <span class="bold"><strong>Si</strong></span>
and <span class="bold"><strong>Mi</strong></span> represent a property called <span class="emphasis"><em><span class="bold"><strong>segmentational fineness</strong></span></em></span> or short <span class="emphasis"><em><span class="bold"><strong>fineness</strong></span></em></span>, which is a <span class="emphasis"><em><span class="bold"><strong>type trait</strong></span></em></span> on interval containers.
</p>
<div class="informaltable"><table class="table">
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<code class="computeroutput"><span class="identifier">segmentational_fineness</span><span class="special"><</span></code><span class="bold"><strong>Si</strong></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">value</span></code>
== <span class="bold"><strong>i</strong></span>
</p>
</td></tr>
<tr><td>
<p>
<code class="computeroutput"><span class="identifier">segmentational_fineness</span><span class="special"><</span></code><span class="bold"><strong>Mi</strong></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">value</span></code>
== <span class="bold"><strong>i</strong></span>
</p>
</td></tr>
</tbody>
</table></div>
<p>
Segmentational fineness represents the fact, that for interval containers
holding the same elements, a splitting interval container may contain more
segments as a separating container which in turn may contain more segments
than a joining one. So for an
</p>
<pre class="programlisting"><span class="keyword">operator</span> <span class="special">></span>
</pre>
<p>
where
</p>
<pre class="programlisting"><span class="identifier">x</span> <span class="special">></span> <span class="identifier">y</span> <span class="comment">// means that
</span><span class="identifier">x</span> <span class="identifier">is_finer_than</span> <span class="identifier">y</span>
<span class="comment">// we have
</span>
<span class="identifier">finer</span> <span class="identifier">coarser</span>
<span class="identifier">split_interval_set</span> <span class="identifier">interval_set</span>
<span class="special">></span> <span class="identifier">separate_interval_set</span> <span class="special">></span>
<span class="identifier">split_interval_map</span> <span class="identifier">interval_map</span>
</pre>
<p>
</p>
<p>
This relation is needed to resolve the instantiation of infix operators e.g.
<code class="computeroutput"><span class="identifier">T</span> <span class="keyword">operator</span>
<span class="special">+</span> <span class="special">(</span><span class="identifier">P</span><span class="special">,</span> <span class="identifier">Q</span><span class="special">)</span></code> for two interval container types <code class="computeroutput"><span class="identifier">P</span></code> and <code class="computeroutput"><span class="identifier">Q</span></code>.
If both <code class="computeroutput"><span class="identifier">P</span></code> and <code class="computeroutput"><span class="identifier">Q</span></code> are candidates for the result type <code class="computeroutput"><span class="identifier">T</span></code>, one of them must be chosen by the compiler.
We choose the type that is segmentational finer as result type <code class="computeroutput"><span class="identifier">T</span></code>. This way we do not loose the <span class="emphasis"><em><span class="bold"><strong>segment information</strong></span></em></span> that is stored in the
<span class="emphasis"><em><span class="bold"><strong>finer</strong></span></em></span> one of the container
types <code class="computeroutput"><span class="identifier">P</span></code> and <code class="computeroutput"><span class="identifier">Q</span></code>.
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// overload tables for
</span><span class="identifier">T</span> <span class="keyword">operator</span> <span class="special">+</span> <span class="special">(</span><span class="identifier">T</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">P</span><span class="special">&)</span>
<span class="identifier">T</span> <span class="keyword">operator</span> <span class="special">+</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">P</span><span class="special">&,</span> <span class="identifier">T</span><span class="special">)</span>
<span class="identifier">element</span> <span class="identifier">containers</span><span class="special">:</span> <span class="identifier">interval</span> <span class="identifier">containers</span><span class="special">:</span>
<span class="special">+</span> <span class="special">|</span> <span class="identifier">e</span> <span class="identifier">b</span> <span class="identifier">s</span> <span class="identifier">m</span> <span class="special">+</span> <span class="special">|</span> <span class="identifier">e</span> <span class="identifier">i</span> <span class="identifier">b</span> <span class="identifier">p</span> <span class="identifier">S1</span> <span class="identifier">S2</span> <span class="identifier">S3</span> <span class="identifier">M1</span> <span class="identifier">M3</span>
<span class="special">---+--------</span> <span class="special">---+---------------------------</span>
<span class="identifier">e</span> <span class="special">|</span> <span class="identifier">s</span> <span class="identifier">e</span> <span class="special">|</span> <span class="identifier">S1</span> <span class="identifier">S2</span> <span class="identifier">S3</span>
<span class="identifier">b</span> <span class="special">|</span> <span class="identifier">m</span> <span class="identifier">i</span> <span class="special">|</span> <span class="identifier">S1</span> <span class="identifier">S2</span> <span class="identifier">S3</span>
<span class="identifier">s</span> <span class="special">|</span> <span class="identifier">s</span> <span class="identifier">s</span> <span class="identifier">b</span> <span class="special">|</span> <span class="identifier">M1</span> <span class="identifier">M3</span>
<span class="identifier">m</span> <span class="special">|</span> <span class="identifier">m</span> <span class="identifier">m</span> <span class="identifier">p</span> <span class="special">|</span> <span class="identifier">M1</span> <span class="identifier">M3</span>
<span class="identifier">S1</span> <span class="special">|</span> <span class="identifier">S1</span> <span class="identifier">S1</span> <span class="identifier">S1</span> <span class="identifier">S2</span> <span class="identifier">S3</span>
<span class="identifier">S2</span> <span class="special">|</span> <span class="identifier">S2</span> <span class="identifier">S2</span> <span class="identifier">S2</span> <span class="identifier">S2</span> <span class="identifier">S3</span>
<span class="identifier">S3</span> <span class="special">|</span> <span class="identifier">S3</span> <span class="identifier">S3</span> <span class="identifier">S3</span> <span class="identifier">S3</span> <span class="identifier">S3</span>
<span class="identifier">M1</span> <span class="special">|</span> <span class="identifier">M1</span> <span class="identifier">M1</span> <span class="identifier">M1</span> <span class="identifier">M3</span>
<span class="identifier">M3</span> <span class="special">|</span> <span class="identifier">M3</span> <span class="identifier">M3</span> <span class="identifier">M3</span> <span class="identifier">M3</span>
</pre>
<p>
</p>
<p>
So looking up a type combination for e.g. <code class="computeroutput"><span class="identifier">T</span>
<span class="keyword">operator</span> <span class="special">+</span>
<span class="special">(</span><span class="identifier">interval_map</span><span class="special">,</span> <span class="identifier">split_interval_map</span><span class="special">)</span></code> which is equivalent to <code class="computeroutput"><span class="identifier">T</span>
<span class="keyword">operator</span> <span class="special">+</span>
<span class="special">(</span><span class="identifier">M1</span><span class="special">,</span> <span class="identifier">M3</span><span class="special">)</span></code>
we find for row type <code class="computeroutput"><span class="identifier">M1</span></code> and
column type <code class="computeroutput"><span class="identifier">M3</span></code> that <code class="computeroutput"><span class="identifier">M3</span></code> will be assigned as result type, because
<code class="computeroutput"><span class="identifier">M3</span></code> is finer than <code class="computeroutput"><span class="identifier">M1</span></code>. So this type combination will result
in choosing this
</p>
<pre class="programlisting"><span class="identifier">split_interval_map</span> <span class="keyword">operator</span> <span class="special">+</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">interval_map</span><span class="special">&,</span> <span class="identifier">split_interval_map</span><span class="special">)</span>
</pre>
<p>
implementation by the compiler.
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2007 -2010 Joachim Faulhaber<br>Copyright © 1999 -2006 Cortex Software GmbH<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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