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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>

2
doc/html/boost_optional/synopsis.html
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@ -81,7 +81,7 @@
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get_ptr</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
<span class="identifier">T</span><span class="special">*</span> <span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
<span class="keyword">operator</span> <span class="identifier">unspecified</span><span class="special">-</span><span class="keyword">bool</span><span class="special">-</span><span class="identifier">type</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_bool"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
<span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_bool"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
<span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_not"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>

2
doc/html/index.html
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@ -163,7 +163,7 @@
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"><p><small>Last revised: April 11, 2014 at 13:25:26 GMT</small></p></td>
<td align="left"><p><small>Last revised: April 26, 2014 at 08:58:33 GMT</small></p></td>
<td align="right"><div class="copyright-footer"></div></td>
</tr></table>
<hr>

8
doc/reference.qbk
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@ -66,7 +66,7 @@
T const* get_ptr() const ; ``[link reference_optional_get_ptr __GO_TO__]``
T* get_ptr() ; ``[link reference_optional_get_ptr __GO_TO__]``
operator unspecified-bool-type() const ; ``[link reference_optional_operator_bool __GO_TO__]``
explicit operator bool() const ; ``[link reference_optional_operator_bool __GO_TO__]``
bool operator!() const ; ``[link reference_optional_operator_not __GO_TO__]``
@ -657,11 +657,11 @@ __SPACE__
[#reference_optional_operator_bool]
[: `optional<T>::operator `['unspecified-bool-type]`() const ;`]
[: `explicit optional<T>::operator bool() const ;`]
* [*Returns:] An unspecified value which if used on a boolean context
is equivalent to (`get_ptr() != 0`)
* [*Returns:] `get_ptr() != 0`.
* [*Throws:] Nothing.
* [*Notes:] On compilers that do not support explicit conversion operators this falls back to safe-bool idiom.
* [*Example:]
``
optional<T> def ;