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Fixed value_init test + doc, according to change of boost::initialized_value, revision [45685]

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[SVN r45686]
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Niels Dekker 2008-05-23 16:48:10 +00:00
parent 8efae71f4a
commit 67f3ca090a
2 changed files with 20 additions and 14 deletions
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29
value_init.htm
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@ -28,12 +28,12 @@
</ul> </ul>
<dl class="page-index"> <dl class="page-index">
<dt><a href="#types">Types</a></dt> <dt><a href="#types">Types and objects</a></dt>
</dl> </dl>
<ul> <ul>
<li><a href="#val_init"><code>template class value_initialized&lt;T&gt;</code></a></li> <li><a href="#val_init"><code>template class value_initialized&lt;T&gt;</code></a></li>
<li><a href="#initialized_value"><code>class initialized_value</code></a></li> <li><a href="#initialized_value"><code>initialized_value</code></a></li>
</ul> </ul>
<a href="#acknowledgements">Acknowledgements</a><br> <a href="#acknowledgements">Acknowledgements</a><br>
@ -53,7 +53,7 @@ union and class types.
Moreover, <code>value_initialized</code> offers a workaround to various Moreover, <code>value_initialized</code> offers a workaround to various
compiler issues regarding value-initialization. compiler issues regarding value-initialization.
Furthermore a convenience class, <code>initialized_value</code> is provided, Furthermore, a <code>const</code> object, <code>initialized_value</code> is provided,
to avoid repeating the type name when retrieving the value from a to avoid repeating the type name when retrieving the value from a
<code>value_initialized&lt;T&gt;</code> object. <code>value_initialized&lt;T&gt;</code> object.
<br> <br>
@ -123,12 +123,12 @@ constructed by the following declaration:
</pre> </pre>
</p> </p>
<p> <p>
The convenience class <a href="#initialized_value"><code>initialized_value</code></a> The <code>const</code> object <a href="#initialized_value"><code>initialized_value</code></a>
allows value-initializing a variable as follows: allows value-initializing a variable as follows:
<pre> <pre>
T var = initialized_value(); T var = initialized_value ;
</pre> </pre>
This form of initialization is also very similar to <code>T4 var4 = T4()</code>, This form of initialization is semantically equivalent to <code>T4 var4 = T4()</code>,
but robust against the aforementioned compiler issues. but robust against the aforementioned compiler issues.
</p> </p>
@ -249,7 +249,7 @@ offer a workaround to these issues: <code>value_initialized</code> will now clea
its internal data, prior to constructing the object that it contains. its internal data, prior to constructing the object that it contains.
</p> </p>
<h2><a name="types"></a>Types</h2> <h2><a name="types"></a>Types and objects</h2>
<h2><a name="val_init"><code>template class value_initialized&lt;T&gt;</code></a></h2> <h2><a name="val_init"><code>template class value_initialized&lt;T&gt;</code></a></h2>
@ -312,19 +312,22 @@ the wrapped object is always performed with the <code>get()</code> idiom:</p>
<pre>value_initialized&lt;int&gt; x ;<br>get(x) = 1 ; // OK<br><br>value_initialized&lt;int const&gt; cx ;<br>get(x) = 1 ; // ERROR: Cannot modify a const object<br><br>value_initialized&lt;int&gt; const x_c ;<br>get(x_c) = 1 ; // ERROR: Cannot modify a const object<br><br>value_initialized&lt;int const&gt; const cx_c ;<br>get(cx_c) = 1 ; // ERROR: Cannot modify a const object<br></pre> <pre>value_initialized&lt;int&gt; x ;<br>get(x) = 1 ; // OK<br><br>value_initialized&lt;int const&gt; cx ;<br>get(x) = 1 ; // ERROR: Cannot modify a const object<br><br>value_initialized&lt;int&gt; const x_c ;<br>get(x_c) = 1 ; // ERROR: Cannot modify a const object<br><br>value_initialized&lt;int const&gt; const cx_c ;<br>get(cx_c) = 1 ; // ERROR: Cannot modify a const object<br></pre>
<h2><a name="initialized_value"><code>class initialized_value</code></a></h2> <h2><a name="initialized_value"><code>initialized_value</code></a></h2>
<pre> <pre>
namespace boost { namespace boost {
class initialized_value class initialized_value_t
{ {
public : public :
template &lt;class T&gt; operator T() const ; template &lt;class T&gt; operator T() const ;
}; };
initialized_value_t const initialized_value = {} ;
} // namespace boost } // namespace boost
</pre> </pre>
The class <code>initialized_value</code> provides a convenient way to get <code>initialized_value</code> provides a convenient way to get
an initialized value: its conversion operator provides an appropriate an initialized value: its conversion operator provides an appropriate
<em>value-initialized</em> object for any CopyConstructible type. <em>value-initialized</em> object for any CopyConstructible type.
@ -343,7 +346,7 @@ is rather short now (<code>T</code>), but could of course be
more like <code>Namespace::Template&lt;Arg&gt;::Type</code>. more like <code>Namespace::Template&lt;Arg&gt;::Type</code>.
Instead, one could use <code>initialized_value</code> as follows: Instead, one could use <code>initialized_value</code> as follows:
<pre> <pre>
T var = initialized_value(); T var = initialized_value ;
</pre> </pre>
<h3><a name="references">References</a></h3> <h3><a name="references">References</a></h3>
@ -368,13 +371,15 @@ Special thanks to Bj&ouml;rn Karlsson who carefully edited and completed this do
<p>value_initialized was reimplemented by Fernando Cacciola and Niels Dekker <p>value_initialized was reimplemented by Fernando Cacciola and Niels Dekker
for Boost release version 1.35 (2008), offering a workaround to various compiler issues. for Boost release version 1.35 (2008), offering a workaround to various compiler issues.
</p> </p>
<p>initialized_value was written by Niels Dekker, and added to Boost release version 1.36 (2008).
</p>
<p>Developed by <a href="mailto:fernando_cacciola@hotmail.com">Fernando Cacciola</a>, <p>Developed by <a href="mailto:fernando_cacciola@hotmail.com">Fernando Cacciola</a>,
the latest version of this file can be found at <a the latest version of this file can be found at <a
href="http://www.boost.org">www.boost.org</a>. href="http://www.boost.org">www.boost.org</a>.
</p> </p>
<hr> <hr>
<p>Revised 16 January 2008</p> <p>Revised 23 May 2008</p>
<p>&copy; Copyright Fernando Cacciola, 2002, 2008.</p> <p>&copy; Copyright Fernando Cacciola, 2002, 2008.</p>

5
value_init_test.cpp
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@ -7,7 +7,8 @@
// Test program for "boost/utility/value_init.hpp" // Test program for "boost/utility/value_init.hpp"
// //
// 21 Ago 2002 (Created) Fernando Cacciola // 21 Ago 2002 (Created) Fernando Cacciola
// 18 Feb 2008 (Added tests regarding compiler issues and initialized_value) Fernando Cacciola, Niels Dekker // 15 Jan 2008 (Added tests regarding compiler issues) Fernando Cacciola, Niels Dekker
// 23 May 2008 (Added tests regarding initialized_value) Niels Dekker
#include <cstring> // For memcmp. #include <cstring> // For memcmp.
#include <iostream> #include <iostream>
@ -183,7 +184,7 @@ struct CopyFunctionCallTester
template<class T> template<class T>
void check_initialized_value ( T const& y ) void check_initialized_value ( T const& y )
{ {
T initializedValue = boost::initialized_value() ; T initializedValue = boost::initialized_value ;
BOOST_CHECK ( y == initializedValue ) ; BOOST_CHECK ( y == initializedValue ) ;
} }