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<html>
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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="typeof.refe"></a>Reference</h2></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="refe.html#typeof.auto">AUTO, AUTO_TPL</a></span></dt>
<dt><span class="section"><a href="refe.html#typeof.compl">COMPLIANT</a></span></dt>
<dt><span class="section"><a href="refe.html#typeof.incr">INCREMENT_REGISTRATION_GROUP</a></span></dt>
<dt><span class="section"><a href="refe.html#typeof.inte">INTEGRAL</a></span></dt>
<dt><span class="section"><a href="refe.html#typeof.limit_func">LIMIT_FUNCTION_ARITY</a></span></dt>
<dt><span class="section"><a href="refe.html#typeof.messages">MESSAGES</a></span></dt>
<dt><span class="section"><a href="refe.html#typeof.limit_size">LIMIT_SIZE</a></span></dt>
<dt><span class="section"><a href="refe.html#typeof.regtype">REGISTER_TYPE</a></span></dt>
<dt><span class="section"><a href="refe.html#typeof.regtemp">REGISTER_TEMPLATE</a></span></dt>
<dt><span class="section"><a href="refe.html#typeof.temp">TEMPLATE</a></span></dt>
<dt><span class="section"><a href="refe.html#typeof.typo">TYPEOF, TYPEOF_TPL</a></span></dt>
<dt><span class="section"><a href="refe.html#typeof.typn">TYPEOF_NESTED_TYPEDEF, TYPEOF_NESTED_TYPEDEF_TPL</a></span></dt>
</dl></div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.auto"></a>AUTO, AUTO_TPL</h3></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">BOOST_AUTO</span></code> macro emulates
the proposed <code class="computeroutput"><span class="keyword">auto</span></code> keyword in
C++.
</p>
<h5>
<a name="auto.usage"></a>
Usage
</h5>
<pre class="programlisting"><span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">var</span><span class="special">,</span><span class="identifier">expr</span><span class="special">)</span>
<span class="identifier">BOOST_AUTO_TPL</span><span class="special">(</span><span class="identifier">var</span><span class="special">,</span><span class="identifier">expr</span><span class="special">)</span>
</pre>
<div class="variablelist">
<p class="title"><b>Arguments</b></p>
<dl>
<dt><span class="term">var</span></dt>
<dd><p>
a variable to be initialized with the expression
</p></dd>
<dt><span class="term">expr</span></dt>
<dd><p>
a valid c++ expression
</p></dd>
</dl>
</div>
<h5>
<a name="auto.remarks"></a>
Remarks
</h5>
<p>
If you want to use <code class="computeroutput"><span class="keyword">auto</span></code> in a
template-context, use <code class="computeroutput"><span class="identifier">BOOST_AUTO_TPL</span><span class="special">(</span><span class="identifier">expr</span><span class="special">)</span></code>,
which takes care of the <code class="computeroutput"><span class="keyword">typename</span></code>
keyword inside the <code class="computeroutput"><span class="keyword">auto</span></code> expression.
</p>
<h5>
<a name="auto.sample_code"></a>
Sample Code
</h5>
<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
<span class="special">{</span>
<span class="identifier">length</span><span class="special">::</span><span class="identifier">meter</span> <span class="identifier">a</span><span class="special">(</span><span class="number">5</span><span class="special">);</span>
<span class="identifier">force</span><span class="special">::</span><span class="identifier">newton</span> <span class="identifier">b</span><span class="special">(</span><span class="number">6</span><span class="special">);</span>
<span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">c</span><span class="special">,</span> <span class="identifier">a</span> <span class="special">*</span> <span class="identifier">b</span><span class="special">);</span>
<span class="special">}</span>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.compl"></a>COMPLIANT</h3></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_COMPLIANT</span></code>
macro can be used to force the emulation mode. Define it if your compiler
by default uses another mode, such as native <code class="computeroutput"><span class="identifier">typeof</span></code>
or Microsoft-specific trick, but you want to use the emulation mode, for
example for portability reasons.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.incr"></a>INCREMENT_REGISTRATION_GROUP</h3></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP</span></code>
macro ensures that type registrations in different header files receive unique
identifiers.
</p>
<h5>
<a name="incr.usage"></a>
Usage
</h5>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="identifier">BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP</span><span class="special">()</span>
</pre>
<h5>
<a name="incr.remarks"></a>
Remarks
</h5>
<p>
specified once in every cpp/hpp file where any registration is performed,
before any registration.
</p>
<h5>
<a name="incr.sample_code"></a>
Sample Code
</h5>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="identifier">BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP</span><span class="special">()</span>
<span class="keyword">class</span> <span class="identifier">X</span><span class="special">;</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TYPE</span><span class="special">(</span><span class="identifier">X</span><span class="special">)</span>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.inte"></a>INTEGRAL</h3></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_INTEGRAL</span></code>
macro is used when registering an integral template parameter using <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span></code>.
</p>
<p>
Useful for <code class="computeroutput"><span class="keyword">enum</span></code>s and dependent
integral template parameters.
</p>
<h5>
<a name="inte.usage"></a>
Usage
</h5>
<pre class="programlisting"><span class="identifier">BOOST_TYPEOF_INTEGRAL</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span>
</pre>
<div class="variablelist">
<p class="title"><b>Arguments</b></p>
<dl>
<dt><span class="term">x</span></dt>
<dd><p>
a fully qualified integral type or enum
</p></dd>
</dl>
</div>
<h5>
<a name="inte.remarks"></a>
Remarks
</h5>
<p>
A short syntax has been implemented for the built in types (int, bool, long,
unsigned long, etc.) Other non-type template parameters (e.g. pointer to
member) are not supported.
</p>
<h5>
<a name="inte.sample_code"></a>
Sample Code
</h5>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="identifier">BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP</span><span class="special">()</span>
<span class="keyword">namespace</span> <span class="identifier">foo</span>
<span class="special">{</span>
<span class="keyword">enum</span> <span class="identifier">color</span> <span class="special">{</span><span class="identifier">red</span><span class="special">,</span> <span class="identifier">green</span><span class="special">,</span> <span class="identifier">blue</span><span class="special">};</span>
<span class="keyword">template</span><span class="special"><</span><span class="identifier">color</span> <span class="identifier">C0</span><span class="special">,</span><span class="keyword">typename</span> <span class="identifier">T1</span><span class="special">></span>
<span class="keyword">class</span> <span class="identifier">class_with_enum</span> <span class="special">{};</span>
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T0</span><span class="special">,</span><span class="identifier">T0</span> <span class="identifier">I1</span><span class="special">></span>
<span class="keyword">class</span> <span class="identifier">class_with_dependent_non_type</span> <span class="special">{};</span>
<span class="special">}</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span><span class="special">(</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">class_with_enum</span><span class="special">,</span>
<span class="special">(</span><span class="identifier">BOOST_TYPEOF_INTEGRAL</span><span class="special">(</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">color</span><span class="special">))</span>
<span class="special">(</span><span class="keyword">typename</span><span class="special">)</span>
<span class="special">)</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span><span class="special">(</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">class_with_dependent_non_type</span><span class="special">,</span>
<span class="special">(</span><span class="keyword">typename</span><span class="special">)</span>
<span class="special">(</span><span class="identifier">BOOST_TYPEOF_INTEGRAL</span><span class="special">(</span><span class="identifier">P0</span><span class="special">))</span>
<span class="special">)</span>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.limit_func"></a>LIMIT_FUNCTION_ARITY</h3></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_LIMIT_FUNCTION_ARITY</span></code>
macro defines how many parameters are supported for functios, and applies
to functions, function pointers, function references, and member function
pointers. The default value is 10. Redefine if you want the Typeof Library
to handle functions with more parameters.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.messages"></a>MESSAGES</h3></div></div></div>
<p>
Define <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_MESSAGE</span></code>
before including boost/typeof/typeof.hpp to include messages "using
typeof emulation" and "using native typeof". By default, these
messages will not be displayed.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.limit_size"></a>LIMIT_SIZE</h3></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_LIMIT_SIZE</span></code>
macro defines the size of the compile-time sequence used to encode a type.
The default value is 50. Increase it if you want the Typeof Library to handle
very complex types, although this possibility is limited by the maximum number
of template parameters supported by your compiler. On the other hand, if
you work only with very simple types, decreasing this number may help to
boost compile-time performance.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.regtype"></a>REGISTER_TYPE</h3></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_REGISTER_TYPE</span></code>
macro informs the Typeof Library about the existence of a type
</p>
<h5>
<a name="regtype.usage"></a>
Usage
</h5>
<pre class="programlisting"><span class="identifier">BOOST_TYPEOF_REGISTER_TYPE</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span>
</pre>
<div class="variablelist">
<p class="title"><b>Arguments</b></p>
<dl>
<dt><span class="term">x</span></dt>
<dd><p>
a fully qualified type
</p></dd>
</dl>
</div>
<h5>
<a name="regtype.remarks"></a>
Remarks
</h5>
<p>
Must be used in the global namespace
</p>
<h5>
<a name="regtype.sample_code"></a>
Sample Code
</h5>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="identifier">BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP</span><span class="special">()</span>
<span class="keyword">namespace</span> <span class="identifier">foo</span>
<span class="special">{</span>
<span class="keyword">class</span> <span class="identifier">bar</span> <span class="special">{};</span>
<span class="keyword">enum</span> <span class="identifier">color</span> <span class="special">{</span><span class="identifier">red</span><span class="special">,</span> <span class="identifier">green</span><span class="special">,</span> <span class="identifier">blue</span><span class="special">};</span>
<span class="special">}</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TYPE</span><span class="special">(</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">bar</span><span class="special">)</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TYPE</span><span class="special">(</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">color</span><span class="special">)</span>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.regtemp"></a>REGISTER_TEMPLATE</h3></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span></code>
macro informs the Typeof Library about the existence of a template and describes
its parameters
</p>
<h5>
<a name="regtemp.usage"></a>
Usage
</h5>
<pre class="programlisting"><span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span><span class="special">(</span><span class="identifier">x</span><span class="special">,</span> <span class="identifier">n</span><span class="special">)</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span><span class="special">(</span><span class="identifier">x</span><span class="special">,</span> <span class="identifier">seq</span><span class="special">)</span>
</pre>
<div class="variablelist">
<p class="title"><b>Arguments</b></p>
<dl>
<dt><span class="term">x</span></dt>
<dd><p>
a fully qualified template
</p></dd>
<dt><span class="term">n</span></dt>
<dd><p>
the number of template arguments. Only valid if all template arguments
are typenames
</p></dd>
<dt><span class="term">seq</span></dt>
<dd><p>
a sequence of template arguments. Must be used when integral or template
template parameters are present
</p></dd>
</dl>
</div>
<h5>
<a name="regtemp.remarks"></a>
Remarks
</h5>
<p>
Must be used in the global namespace.
</p>
<p>
The library allows registration of templates with type, integral, and template
template parameters:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
A type template parameter is described by the <code class="computeroutput"><span class="special">(</span><span class="keyword">class</span><span class="special">)</span></code>
or <code class="computeroutput"><span class="special">(</span><span class="keyword">typename</span><span class="special">)</span></code> sequence element
</li>
<li class="listitem">
A template parameter of a well-known integral type can be described by
simply supplying its type, like <code class="computeroutput"><span class="special">(</span><span class="keyword">unsigned</span> <span class="keyword">int</span><span class="special">)</span></code>. The following well-known integral types
are supported:
<div class="itemizedlist"><ul class="itemizedlist" type="circle">
<li class="listitem">
<code class="computeroutput"><span class="special">[</span><span class="keyword">signed</span><span class="special">/</span><span class="keyword">unsigned</span><span class="special">]</span> <span class="keyword">char</span></code>
</li>
<li class="listitem">
<code class="computeroutput"><span class="special">[</span><span class="keyword">unsigned</span><span class="special">]</span> <span class="keyword">short</span></code>
</li>
<li class="listitem">
<code class="computeroutput"><span class="special">[</span><span class="keyword">unsigned</span><span class="special">]</span> <span class="keyword">int</span></code>
</li>
<li class="listitem">
<code class="computeroutput"><span class="special">[</span><span class="keyword">unsigned</span><span class="special">]</span> <span class="keyword">long</span></code>
</li>
<li class="listitem">
<code class="computeroutput"><span class="keyword">unsigned</span></code>
</li>
<li class="listitem">
<code class="computeroutput"><span class="keyword">bool</span></code>
</li>
<li class="listitem">
<code class="computeroutput"><span class="identifier">size_t</span></code>
</li>
</ul></div>
</li>
<li class="listitem">
Enums and typedefs of integral types, need to be described explicitly
with the <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_INTEGRAL</span></code>
macro, like <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_TYPEOF_INTEGRAL</span><span class="special">(</span><span class="identifier">MyEnum</span><span class="special">))</span></code>
</li>
<li class="listitem">
Template template parameters are described with the <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_TEMPLATE</span></code>
macro, like: <code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_TYPEOF_TEMPLATE</span><span class="special">((</span><span class="keyword">class</span><span class="special">)(</span><span class="keyword">unsigned</span> <span class="keyword">int</span><span class="special">)))</span></code>.
In case of all type parameters this can be shortened to something like
<code class="computeroutput"><span class="special">(</span><span class="identifier">BOOST_TYPEOF_TEMPLATE</span><span class="special">(</span><span class="number">2</span><span class="special">))</span></code>.
The nested template template parameters are not supported.
</li>
</ul></div>
<h5>
<a name="regtemp.sample_code"></a>
Sample Code
</h5>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="identifier">BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP</span><span class="special">()</span>
<span class="keyword">namespace</span> <span class="identifier">foo</span>
<span class="special">{</span>
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T0</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T1</span><span class="special">></span>
<span class="keyword">class</span> <span class="identifier">simple_template</span> <span class="special">{};</span>
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T0</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">I1</span><span class="special">></span>
<span class="keyword">class</span> <span class="identifier">class_with_integral_constant</span> <span class="special">{};</span>
<span class="special">}</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span><span class="special">(</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">simple_template</span><span class="special">,</span> <span class="number">2</span><span class="special">)</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span><span class="special">(</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">class_with_integral_constant</span><span class="special">,</span> <span class="special">(</span><span class="keyword">typename</span><span class="special">)(</span><span class="keyword">int</span><span class="special">))</span>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.temp"></a>TEMPLATE</h3></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_TEMPLATE</span></code>
macro is used when registering template template parameters using <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span></code>.
</p>
<h5>
<a name="temp.usage"></a>
Usage
</h5>
<pre class="programlisting"><span class="identifier">BOOST_TYPEOF_TEMPLATE</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span>
<span class="identifier">BOOST_TYPEOF_TEMPLATE</span><span class="special">(</span><span class="identifier">seq</span><span class="special">)</span>
</pre>
<div class="variablelist">
<p class="title"><b>Arguments</b></p>
<dl>
<dt><span class="term">n</span></dt>
<dd><p>
the number of template arguments. Only valid if all template arguments
are typenames
</p></dd>
<dt><span class="term">seq</span></dt>
<dd><p>
a sequence of template arguments. Must be used when there are integral
constants in the nested template
</p></dd>
</dl>
</div>
<h5>
<a name="temp.remarks"></a>
Remarks
</h5>
<p>
Can not be used to register nested template template parameters.
</p>
<h5>
<a name="temp.sample_code"></a>
Sample Code
</h5>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="identifier">BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP</span><span class="special">()</span>
<span class="keyword">namespace</span> <span class="identifier">foo</span>
<span class="special">{</span>
<span class="keyword">enum</span> <span class="identifier">color</span> <span class="special">{</span><span class="identifier">red</span><span class="special">,</span> <span class="identifier">green</span><span class="special">,</span> <span class="identifier">blue</span><span class="special">};</span>
<span class="keyword">template</span><span class="special"><</span><span class="identifier">color</span> <span class="identifier">C0</span><span class="special">,</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span><span class="special">></span> <span class="keyword">class</span> <span class="identifier">T1</span><span class="special">></span>
<span class="keyword">class</span> <span class="identifier">nested_template_class</span> <span class="special">{};</span>
<span class="keyword">template</span><span class="special"><</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span><span class="special">,</span> <span class="keyword">unsigned</span> <span class="keyword">char</span><span class="special">></span> <span class="keyword">class</span> <span class="identifier">T1</span><span class="special">></span>
<span class="keyword">class</span> <span class="identifier">nested_with_integral</span> <span class="special">{};</span>
<span class="special">}</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span><span class="special">(</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">nested_template_class</span><span class="special">,</span>
<span class="special">(</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">color</span><span class="special">)</span>
<span class="special">(</span><span class="identifier">BOOST_TYPEOF_TEMPLATE</span><span class="special">(</span><span class="number">1</span><span class="special">))</span>
<span class="special">)</span>
<span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span><span class="special">(</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">nested_with_integral</span><span class="special">,</span>
<span class="special">(</span><span class="identifier">BOOST_TYPEOF_TEMPLATE</span><span class="special">((</span><span class="keyword">typename</span><span class="special">)(</span><span class="keyword">unsigned</span> <span class="keyword">char</span><span class="special">)))</span>
<span class="special">)</span>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.typo"></a>TYPEOF, TYPEOF_TPL</h3></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">BOOST_TYPEOF</span></code> macro calculates
the type of an expression, but removes the top-level qualifiers, <code class="computeroutput"><span class="keyword">const</span><span class="special">&</span></code>
</p>
<h5>
<a name="typo.usage"></a>
Usage
</h5>
<pre class="programlisting"><span class="identifier">BOOST_TYPEOF</span><span class="special">(</span><span class="identifier">expr</span><span class="special">)</span>
<span class="identifier">BOOST_TYPEOF_TPL</span><span class="special">(</span><span class="identifier">expr</span><span class="special">)</span>
</pre>
<div class="variablelist">
<p class="title"><b>Arguments</b></p>
<dl>
<dt><span class="term">expr</span></dt>
<dd><p>
a valid c++ expression that can be bound to const T&
</p></dd>
</dl>
</div>
<h5>
<a name="typo.remarks"></a>
Remarks
</h5>
<p>
If you want to use <code class="computeroutput"><span class="identifier">typeof</span></code>
in a template-context, use <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_TPL</span><span class="special">(</span><span class="identifier">expr</span><span class="special">)</span></code>,
which takes care of <code class="computeroutput"><span class="keyword">typename</span></code>
inside the <code class="computeroutput"><span class="identifier">typeof</span></code> expression.
</p>
<h5>
<a name="typo.sample_code"></a>
Sample Code
</h5>
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">A</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">B</span><span class="special">></span>
<span class="keyword">struct</span> <span class="identifier">result_of_conditional</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="identifier">BOOST_TYPEOF_TPL</span><span class="special">(</span><span class="keyword">true</span><span class="special">?</span><span class="identifier">A</span><span class="special">():</span><span class="identifier">B</span><span class="special">())</span> <span class="identifier">type</span><span class="special">;</span>
<span class="special">};</span>
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">A</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">B</span><span class="special">></span>
<span class="identifier">result_of_conditional</span><span class="special"><</span><span class="identifier">A</span><span class="special">,</span> <span class="identifier">B</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">min</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">A</span><span class="special">&</span> <span class="identifier">a</span><span class="special">,</span><span class="keyword">const</span> <span class="identifier">B</span><span class="special">&</span> <span class="identifier">b</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">a</span> <span class="special"><</span> <span class="identifier">b</span> <span class="special">?</span> <span class="identifier">a</span> <span class="special">:</span> <span class="identifier">b</span><span class="special">;</span>
<span class="special">}</span>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="typeof.typn"></a>TYPEOF_NESTED_TYPEDEF, TYPEOF_NESTED_TYPEDEF_TPL</h3></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">TYPEOF_NESTED_TYPEDEF</span></code>
macro works in much the same way as the 'TYPEOF' macro does, but workarounds
several compiler deficiencies.
</p>
<h5>
<a name="typn.usage"></a>
Usage
</h5>
<pre class="programlisting"><span class="identifier">BOOST_TYPEOF_NESTED_TYPEDEF</span><span class="special">(</span><span class="identifier">name</span><span class="special">,</span><span class="identifier">expr</span><span class="special">)</span>
<span class="identifier">BOOST_TYPEOF_NESTED_TYPEDEF_TPL</span><span class="special">(</span><span class="identifier">name</span><span class="special">,</span><span class="identifier">expr</span><span class="special">)</span>
</pre>
<div class="variablelist">
<p class="title"><b>Arguments</b></p>
<dl>
<dt><span class="term">name</span></dt>
<dd>
<p>
a valid identifier to nest the typeof operation inside
</p>
<p>
expr
</p>
<p>
a valid c++ expression that can be bound to const T&
</p>
</dd>
</dl>
</div>
<h5>
<a name="typn.remarks"></a>
Remarks
</h5>
<p>
'typeof_nested_typedef' nests the 'typeof' operation inside a struct. By
doing this, the 'typeof' operation can be split into two steps, deconfusing
several compilers (notably VC7.1 and VC8.0) on the way. This also removes
the limitation imposed by <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_LIMIT_SIZE</span></code>
and allows you to use 'typeof' on much larger expressions.
</p>
<p>
If you want to use <code class="computeroutput"><span class="identifier">typeof_nested_typedef</span></code>
in a template-context, use <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_NESTED_TYPEDEF_TPL</span><span class="special">(</span><span class="identifier">name</span><span class="special">,</span><span class="identifier">expr</span><span class="special">)</span></code>,
which takes care of <code class="computeroutput"><span class="keyword">typename</span></code>
inside the <code class="computeroutput"><span class="identifier">typeof</span></code> expression.
</p>
<p>
'typeof_nested_typedef' can not be used at function/block scope.
</p>
<h5>
<a name="typn.sample_code"></a>
Sample Code
</h5>
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">A</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">B</span><span class="special">></span>
<span class="keyword">struct</span> <span class="identifier">result_of_conditional</span>
<span class="special">{</span>
<span class="identifier">BOOST_TYPEOF_NESTED_TYPEDEF_TPL</span><span class="special">(</span><span class="identifier">nested</span><span class="special">,</span><span class="keyword">true</span><span class="special">?</span><span class="identifier">A</span><span class="special">():</span><span class="identifier">B</span><span class="special">())</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">nested</span><span class="special">::</span><span class="identifier">type</span> <span class="identifier">type</span><span class="special">;</span>
<span class="special">};</span>
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">A</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">B</span><span class="special">></span>
<span class="identifier">result_of_conditional</span><span class="special"><</span><span class="identifier">A</span><span class="special">,</span> <span class="identifier">B</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">min</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">A</span><span class="special">&</span> <span class="identifier">a</span><span class="special">,</span><span class="keyword">const</span> <span class="identifier">B</span><span class="special">&</span> <span class="identifier">b</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">a</span> <span class="special"><</span> <span class="identifier">b</span> <span class="special">?</span> <span class="identifier">a</span> <span class="special">:</span> <span class="identifier">b</span><span class="special">;</span>
<span class="special">}</span>
</pre>
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="right"><div class="copyright-footer">Copyright © 2004, 2005 Arkadiy Vertleyb, Peder Holt<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>)
</p>
</div></td>
</tr></table>
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