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<div class="section" title="Numeric Converter Policy Classes">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="boost_numericconversion.numeric_converter_policy_classes"></a><a class="link" href="numeric_converter_policy_classes.html" title="Numeric Converter Policy Classes">Numeric
Converter Policy Classes</a>
</h2></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.enum_range_check_result">enum
range_check_result</a></span></dt>
<dt><span class="section"><a href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_overflowhandler">Policy
OverflowHandler</a></span></dt>
<dt><span class="section"><a href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder">Policy
Float2IntRounder</a></span></dt>
<dt><span class="section"><a href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_rawconverter">Policy
RawConverter</a></span></dt>
<dt><span class="section"><a href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_userrangechecker">Policy
UserRangeChecker</a></span></dt>
</dl></div>
<div class="section" title="enum range_check_result">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_numericconversion.numeric_converter_policy_classes.enum_range_check_result"></a><a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.enum_range_check_result" title="enum range_check_result">enum
range_check_result</a>
</h3></div></div></div>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">numeric</span> <span class="special">{</span>
<span class="keyword">enum</span> <span class="identifier">range_check_result</span>
<span class="special">{</span>
<span class="identifier">cInRange</span> <span class="special">,</span>
<span class="identifier">cNegOverflow</span> <span class="special">,</span>
<span class="identifier">cPosOverflow</span>
<span class="special">}</span> <span class="special">;</span>
<span class="special">}</span> <span class="special">}</span>
</pre>
<p>
Defines the values returned by <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">numeric</span><span class="special">::</span><span class="identifier">converter</span><span class="special">&lt;&gt;::</span><span class="identifier">out_of_range</span><span class="special">()</span></code>
</p>
</div>
<div class="section" title="Policy OverflowHandler">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_numericconversion.numeric_converter_policy_classes.policy_overflowhandler"></a><a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_overflowhandler" title="Policy OverflowHandler">Policy
OverflowHandler</a>
</h3></div></div></div>
<p>
This <span class="emphasis"><em>stateless</em></span> non-template policy class must be a
<span class="emphasis"><em>function object</em></span> and is called to administrate the result
of the range checking. It can throw an exception if overflow has been detected
by the range checking as indicated by its argument. If it throws, is is recommended
that it be <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">bad_cast</span></code> or derived.
</p>
<p>
It must have the following interface (it does not has to be a template class):
</p>
<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">YourOverflowHandlerPolicy</span>
<span class="special">{</span>
<span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()</span> <span class="special">(</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_check_result</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// throw bad_cast or derived
</span><span class="special">}</span> <span class="special">;</span>
</pre>
<p>
It is called with the result of the converter's <code class="computeroutput"><span class="identifier">out_of_range</span><span class="special">()</span></code> inside <code class="computeroutput"><span class="identifier">validate_range</span><span class="special">()</span></code>.
</p>
<p>
These are the two overflow handler classes provided by the library:
</p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">numeric</span> <span class="special">{</span>
<span class="keyword">struct</span> <span class="identifier">def_overflow_handler</span>
<span class="special">{</span>
<span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()</span> <span class="special">(</span> <span class="identifier">range_check_result</span> <span class="identifier">r</span> <span class="special">)</span> <span class="comment">// throw bad_numeric_conversion derived
</span> <span class="special">{</span>
<span class="keyword">if</span> <span class="special">(</span> <span class="identifier">r</span> <span class="special">==</span> <span class="identifier">cNegOverflow</span> <span class="special">)</span>
<span class="keyword">throw</span> <span class="identifier">negative_overflow</span><span class="special">()</span> <span class="special">;</span>
<span class="keyword">else</span> <span class="keyword">if</span> <span class="special">(</span> <span class="identifier">r</span> <span class="special">==</span> <span class="identifier">cPosOverflow</span> <span class="special">)</span>
<span class="keyword">throw</span> <span class="identifier">positive_overflow</span><span class="special">()</span> <span class="special">;</span>
<span class="special">}</span>
<span class="special">}</span> <span class="special">;</span>
<span class="keyword">struct</span> <span class="identifier">silent_overflow_handler</span>
<span class="special">{</span>
<span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()</span> <span class="special">(</span> <span class="identifier">range_check_result</span> <span class="special">)</span> <span class="comment">// no-throw
</span> <span class="special">{}</span>
<span class="special">}</span> <span class="special">;</span>
<span class="special">}</span> <span class="special">}</span>
</pre>
<p>
And these are the Exception Classes thrown by the default overflow handler
<a class="link" href="numeric_converter_policy_classes.html#numeric_conversion_policy_overflow_handler_important_note">(see
IMPORTANT note)</a>
</p>
<a name="numeric_conversion_bad_numeric_cast"></a><a name="numeric_conversion_negative_overflow"></a><a name="numeric_conversion_possitive_overflow"></a><pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">numeric</span> <span class="special">{</span>
<span class="keyword">class</span> <span class="identifier">bad_numeric_cast</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">bad_cast</span>
<span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="keyword">virtual</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">what</span><span class="special">()</span> <span class="keyword">const</span> <span class="comment">// throw()
</span> <span class="special">{</span>
<span class="keyword">return</span> <span class="string">"bad numeric conversion: overflow"</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">};</span>
<span class="keyword">class</span> <span class="identifier">negative_overflow</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">bad_numeric_cast</span>
<span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="keyword">virtual</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">what</span><span class="special">()</span> <span class="keyword">const</span> <span class="comment">// throw()
</span> <span class="special">{</span>
<span class="keyword">return</span> <span class="string">"bad numeric conversion: negative overflow"</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">};</span>
<span class="keyword">class</span> <span class="identifier">positive_overflow</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">bad_numeric_cast</span>
<span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="keyword">virtual</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">what</span><span class="special">()</span> <span class="keyword">const</span> <span class="comment">// throw()
</span> <span class="special">{</span>
<span class="keyword">return</span> <span class="string">"bad numeric conversion: positive overflow"</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">};</span>
<span class="special">}</span> <span class="special">}</span>
</pre>
<a name="numeric_conversion_policy_overflow_handler_important_note"></a><p>
</p>
<div class="important" title="Important"><table border="0" summary="Important">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/html/images/important.png"></td>
<th align="left">Important</th>
</tr>
<tr><td align="left" valign="top"><p>
<span class="bold"><strong>RELEASE NOTE for 1.33</strong></span> Previous to boost
version 1.33, the exception class <code class="computeroutput"><span class="identifier">bad_numeric_cast</span></code>
was named <code class="computeroutput"><span class="identifier">bad_numeric_conversion</span></code>.
However, in 1.33, the old function <code class="computeroutput"><span class="identifier">numeric_cast</span><span class="special">&lt;&gt;</span></code> from <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">cast</span><span class="special">.</span><span class="identifier">hpp</span></code>
was completly replaced by the new <code class="computeroutput"><span class="identifier">numeric_cast</span><span class="special">&lt;&gt;</span></code> in <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">numeric</span><span class="special">/</span><span class="identifier">conversion</span><span class="special">/</span><span class="identifier">cast</span><span class="special">.</span><span class="identifier">hpp</span></code>
(and <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">cast</span><span class="special">.</span><span class="identifier">hpp</span></code> is including <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">numeric</span><span class="special">/</span><span class="identifier">conversion</span><span class="special">/</span><span class="identifier">cast</span><span class="special">.</span><span class="identifier">hpp</span></code>
now). That old function which existed in boost for quite some time used
the <code class="computeroutput"><span class="identifier">bad_numeric_cast</span></code> as
its exception type so I decided to avoid backward compatibility problems
by adopting it (guessing that the user base for the old code is wider than
for the new code).
</p></td></tr>
</table></div>
</div>
<div class="section" title="Policy Float2IntRounder">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder"></a><a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder" title="Policy Float2IntRounder">Policy
Float2IntRounder</a>
</h3></div></div></div>
<p>
This <span class="emphasis"><em>stateless</em></span> template policy class specifies the rounding
mode used for <span class="underline">float to integral</span> conversions.
It supplies the <code class="computeroutput"><span class="identifier">nearbyint</span><span class="special">()</span></code> static member function exposed by the converter,
which means that it <span class="underline">publicly inherits from this
policy</span>.
</p>
<p>
The policy must have the following interface:
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">S</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">YourFloat2IntRounderPolicy</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="identifier">S</span> <span class="identifier">source_type</span> <span class="special">;</span>
<span class="keyword">typedef</span> <span class="special">{</span><span class="identifier">S</span> <span class="keyword">or</span> <span class="identifier">S</span> <span class="keyword">const</span><span class="special">&amp;}</span> <span class="identifier">argument_type</span> <span class="special">;</span>
<span class="keyword">static</span> <span class="identifier">source_type</span> <span class="identifier">nearbyint</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span> <span class="special">{</span> <span class="special">...</span> <span class="special">}</span>
<span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">integral_c</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">float_round_style</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">round_</span><span class="special">...&gt;</span> <span class="identifier">round_style</span> <span class="special">;</span>
<span class="special">}</span> <span class="special">;</span>
</pre>
<p>
These are the rounder classes provided by the library (only the specific
parts are shown, see the general policy form above)
</p>
<div class="note" title="Note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/html/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
These classes are not intended to be general purpose rounding functions
but specific policies for <code class="computeroutput"><span class="identifier">converter</span><span class="special">&lt;&gt;</span></code>. This is why they are not function
objects.
</p></td></tr>
</table></div>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">numeric</span> <span class="special">{</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">S</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">Trunc</span>
<span class="special">{</span>
<span class="keyword">static</span> <span class="identifier">source_type</span> <span class="identifier">nearbyint</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
<span class="special">{</span>
<span class="keyword">using</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">floor</span> <span class="special">;</span>
<span class="keyword">using</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">ceil</span> <span class="special">;</span>
<span class="keyword">return</span> <span class="identifier">s</span> <span class="special">&gt;=</span> <span class="keyword">static_cast</span><span class="special">&lt;</span><span class="identifier">S</span><span class="special">&gt;(</span><span class="number">0</span><span class="special">)</span> <span class="special">?</span> <span class="identifier">floor</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">:</span> <span class="identifier">ceil</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">;</span>
<span class="special">}</span>
<span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">integral_c</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">float_round_style</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">round_toward_zero</span><span class="special">&gt;</span> <span class="identifier">round_style</span> <span class="special">;</span>
<span class="special">}</span> <span class="special">;</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">S</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">RoundEven</span>
<span class="special">{</span>
<span class="keyword">static</span> <span class="identifier">source_type</span> <span class="identifier">nearbyint</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">impl</span><span class="special">-</span><span class="identifier">defined</span><span class="special">-</span><span class="identifier">value</span> <span class="special">;</span>
<span class="special">}</span>
<span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">integral_c</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">float_round_style</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">round_to_nearest</span><span class="special">&gt;</span> <span class="identifier">round_style</span> <span class="special">;</span>
<span class="special">}</span> <span class="special">;</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">S</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">Ceil</span>
<span class="special">{</span>
<span class="keyword">static</span> <span class="identifier">source_type</span> <span class="identifier">nearbyint</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
<span class="special">{</span>
<span class="keyword">using</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">ceil</span> <span class="special">;</span>
<span class="keyword">return</span> <span class="identifier">ceil</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">;</span>
<span class="special">}</span>
<span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">integral_c</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">float_round_style</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">round_toward_infinity</span><span class="special">&gt;</span> <span class="identifier">round_style</span> <span class="special">;</span>
<span class="special">}</span> <span class="special">;</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">S</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">Floor</span>
<span class="special">{</span>
<span class="keyword">static</span> <span class="identifier">source_type</span> <span class="identifier">nearbyint</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
<span class="special">{</span>
<span class="keyword">using</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">floor</span> <span class="special">;</span>
<span class="keyword">return</span> <span class="identifier">floor</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">;</span>
<span class="special">}</span>
<span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">integral_c</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">float_round_style</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">round_toward_neg_infinity</span><span class="special">&gt;</span> <span class="identifier">round_style</span> <span class="special">;</span>
<span class="special">}</span> <span class="special">;</span>
<span class="special">}</span> <span class="special">}</span> <span class="comment">// namespace numeric, namespace boost
</span></pre>
<a name="boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder.math_functions_used_by_the_rounder_policies"></a><h5>
<a name="id572764"></a>
<a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder.math_functions_used_by_the_rounder_policies">Math
Functions used by the rounder policies</a>
</h5>
<p>
The rounder policies supplied by this header use math functions <code class="computeroutput"><span class="identifier">floor</span><span class="special">()</span></code>
and <code class="computeroutput"><span class="identifier">ceil</span><span class="special">()</span></code>.
The standard versions of these functions are introduced in context by a using
directive, so in normal conditions, the standard functions will be used.
</p>
<p>
However, if there are other visible corresponding overloads an ambiguity
could arise. In this case, the user can supply her own rounder policy which
could, for instance, use a fully qualified call.
</p>
<p>
This technique allows the default rounder policies to be used directly with
user defined types. The user only requires that suitable overloads of <code class="computeroutput"><span class="identifier">floor</span><span class="special">()</span></code>
and <code class="computeroutput"><span class="identifier">ceil</span><span class="special">()</span></code>
be visible. See also <a class="link" href="type_requirements_and_user_defined_types_support.html" title="Type Requirements and User-defined-types support">User
Defined Numeric Types</a> support.
</p>
</div>
<div class="section" title="Policy RawConverter">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_numericconversion.numeric_converter_policy_classes.policy_rawconverter"></a><a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_rawconverter" title="Policy RawConverter">Policy
RawConverter</a>
</h3></div></div></div>
<p>
This <span class="emphasis"><em>stateless</em></span> template policy class is used to perform
the actual conversion from Source to Target. It supplies the <code class="computeroutput"><span class="identifier">low_level_convert</span><span class="special">()</span></code>
static member function exposed by the converter, which means that it publicly
inherits from this policy.
</p>
<p>
The policy must have the following interface:
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Traits</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">YourRawConverterPolicy</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">result_type</span> <span class="identifier">result_type</span> <span class="special">;</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">argument_type</span> <span class="identifier">argument_type</span> <span class="special">;</span>
<span class="keyword">static</span> <span class="identifier">result_type</span> <span class="identifier">low_level_convert</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="special">&lt;</span><span class="identifier">impl</span> <span class="identifier">defined</span><span class="special">&gt;</span> <span class="special">;</span> <span class="special">}</span>
<span class="special">}</span> <span class="special">;</span>
</pre>
<p>
This policy is mostly provided as a hook for user defined types which don't
support <code class="computeroutput"><span class="keyword">static_cast</span><span class="special">&lt;&gt;</span></code>
conversions to some types
</p>
<p>
This is the only raw converter policy class provided by the library:
</p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">numeric</span> <span class="special">{</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Traits</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">raw_numeric_converter</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">result_type</span> <span class="identifier">result_type</span> <span class="special">;</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">argument_type</span> <span class="identifier">argument_type</span> <span class="special">;</span>
<span class="keyword">static</span> <span class="identifier">result_type</span> <span class="identifier">low_level_convert</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="keyword">static_cast</span><span class="special">&lt;</span><span class="identifier">result_type</span><span class="special">&gt;(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">;</span>
<span class="special">}</span>
<span class="special">}</span> <span class="special">;</span>
<span class="special">}</span> <span class="special">}</span>
</pre>
</div>
<div class="section" title="Policy UserRangeChecker">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_numericconversion.numeric_converter_policy_classes.policy_userrangechecker"></a><a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_userrangechecker" title="Policy UserRangeChecker">Policy
UserRangeChecker</a>
</h3></div></div></div>
<p>
This <span class="emphasis"><em>stateless</em></span> template policy class is used <span class="underline">only if supplied</span> to <span class="bold"><strong>override</strong></span>
the internal range checking logic.
</p>
<p>
It supplies the <code class="computeroutput"><span class="identifier">validate_range</span><span class="special">()</span></code> static member function exposed by the converter,
which means that it publicly inherits from this policy.
</p>
<p>
The policy must have the following interface:
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Traits</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">YourRangeCheckerPolicy</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">argument_type</span> <span class="identifier">argument_type</span> <span class="special">;</span>
<span class="comment">// Determines if the value 's' fits in the range of the Target type.
</span> <span class="keyword">static</span> <span class="identifier">range_check_result</span> <span class="identifier">out_of_range</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span> <span class="special">;</span>
<span class="comment">// Checks whether the value 's' is out_of_range()
</span> <span class="comment">// and passes the result of the check to the OverflowHandler policy.
</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="identifier">validate_range</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
<span class="special">{</span>
<span class="identifier">OverflowHandler</span><span class="special">()(</span> <span class="identifier">out_of_range</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
<span class="special">}</span>
<span class="special">}</span> <span class="special">;</span>
</pre>
<p>
This policy is <span class="bold"><strong>only</strong></span> provided as a hook for
user defined types which require range checking (which is disabled by default
when a UDT is involved). The library provides a class: <code class="computeroutput"><span class="identifier">UseInternalRangeChecker</span><span class="special">{}</span></code>; which is a <span class="emphasis"><em>fake</em></span>
<code class="computeroutput"><span class="identifier">RangeChecker</span></code> policy used
to signal the converter to use its internal range checking implementation.
</p>
</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 -2007 Fernando Luis Cacciola Carballal<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>
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