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Use BOOST_EXPLICIT_OPERATOR_BOOL for optional

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I often have the problem that when I change a std::wstring to boost::optional<std::wstring> and the variable is used as a parameter with Boost.Format, the result silently changes from the string contents to "1".

This change prevents implicit conversion to bool if the compiler supports explicit conversion operators.
This commit is contained in:
Marcel Raad
2014-04-24 10:00:43 +02:00
committed by Andrzej Krzemienski
parent b4738ac07e
commit c7cf80e5df
8 changed files with 46 additions and 23 deletions
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9
doc/html/boost_optional/detailed_semantics.html
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@ -981,16 +981,19 @@
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
</p>
<a name="reference_optional_operator_bool"></a><div class="blockquote"><blockquote class="blockquote"><p>
<code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="keyword">operator</span> </code><span class="emphasis"><em>unspecified-bool-type</em></span><code class="computeroutput"><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
<code class="computeroutput"><span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
</p></blockquote></div>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<span class="bold"><strong>Returns:</strong></span> An unspecified value which if
used on a boolean context is equivalent to (<code class="computeroutput"><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</span></code>)
<span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</span></code>.
</li>
<li class="listitem">
<span class="bold"><strong>Throws:</strong></span> Nothing.
</li>
<li class="listitem">
<span class="bold"><strong>Notes:</strong></span> On compilers that do not support
explicit conversion operators this falls back to safe-bool idiom.
</li>
<li class="listitem">
<span class="bold"><strong>Example:</strong></span>
<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">def</span> <span class="special">;</span>