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- <td valign="top"><img href="index.html" height="164px" src="pre-boost.jpg" alt="Library Documentation Index"></td>
- <td><h2>Safe Numerics</h2></td>
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- <div class="titlepage"><div><div><h3 class="title">
- <a name="safe_numeric.exception_policies"></a>exception_policy<AE, IDB, UB, UV></h3></div></div></div>
- <div class="toc"><dl class="toc">
- <dt><span class="section"><a href="exception_policies.html#idm130202951248">Description</a></span></dt>
- <dt><span class="section"><a href="exception_policies.html#idm130202949952">Template Parameters</a></span></dt>
- <dt><span class="section"><a href="exception_policies.html#idm130202934048">Model of</a></span></dt>
- <dt><span class="section"><a href="exception_policies.html#idm130202932336">Inherited Valid Expressions</a></span></dt>
- <dt><span class="section"><a href="exception_policies.html#idm130202930224">Function Objects</a></span></dt>
- <dt><span class="section"><a href="exception_policies.html#idm130202892272">Policies Provided by the library</a></span></dt>
- <dt><span class="section"><a href="exception_policies.html#idm130202855952">Header</a></span></dt>
- </dl></div>
- <div class="section">
- <div class="titlepage"><div><div><h4 class="title">
- <a name="idm130202951248"></a>Description</h4></div></div></div>
- <p>Create a valid exception policy from 4 function objects. This
- specifies the actions to be taken for different types of invalid
- results.</p>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h4 class="title">
- <a name="idm130202949952"></a>Template Parameters</h4></div></div></div>
- <div class="informaltable"><table class="table">
- <colgroup>
- <col align="left">
- <col align="left">
- <col align="left">
- </colgroup>
- <thead><tr>
- <th align="left">Parameter</th>
- <th align="left">Type Requirements</th>
- <th align="left">Invoked when:</th>
- </tr></thead>
- <tbody>
- <tr>
- <td align="left"><code class="computeroutput">AE</code></td>
- <td align="left">Function object callable with the expression AE(e,
- message)</td>
- <td align="left"><p>The operation cannot produce valid arithmetic result
- such as overflows, divide by zero, etc.</p></td>
- </tr>
- <tr>
- <td align="left"><code class="computeroutput">UB</code></td>
- <td align="left">Function object callable with the expression UB(e,
- message)</td>
- <td align="left"><p>The result is undefined by the C++
- standard</p></td>
- </tr>
- <tr>
- <td align="left"><code class="computeroutput">IDB</code></td>
- <td align="left">Function object callable with the expression IDB(e,</td>
- <td align="left"><p>The result depends upon implementation defined
- behavior according to the C++ standard</p></td>
- </tr>
- <tr>
- <td align="left"><code class="computeroutput">UV</code></td>
- <td align="left">Function object callable with the expression UV(e,
- message)</td>
- <td align="left"><p>A variable is not initialized</p></td>
- </tr>
- </tbody>
- </table></div>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h4 class="title">
- <a name="idm130202934048"></a>Model of</h4></div></div></div>
- <p><a class="link" href="promotion_policy.html" title="PromotionPolicy<PP>">ExceptionPolicy</a></p>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h4 class="title">
- <a name="idm130202932336"></a>Inherited Valid Expressions</h4></div></div></div>
- <p>This class implements all the valid operations from the type
- requirements <a class="link" href="promotion_policy.html" title="PromotionPolicy<PP>">ExceptionPolicy</a>. Aside
- from these, there are no other operations implemented.</p>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h4 class="title">
- <a name="idm130202930224"></a>Function Objects</h4></div></div></div>
- <p>In order to create an exception policy, one needs some function
- objects. The library includes some appropriate examples of these:</p>
- <div class="informaltable"><table class="table">
- <colgroup>
- <col align="left">
- <col align="left">
- </colgroup>
- <thead><tr>
- <th align="left">Name</th>
- <th align="left">Description</th>
- </tr></thead>
- <tbody>
- <tr>
- <td align="left"><code class="computeroutput">ignore_exception</code></td>
- <td align="left">Ignore any runtime exception and just return - thus
- propagating the error. This is what would happen with unsafe data
- types</td>
- </tr>
- <tr>
- <td align="left"><code class="computeroutput">throw_exception</code></td>
- <td align="left">throw an exception of type std::system_error</td>
- </tr>
- <tr>
- <td align="left"><code class="computeroutput">trap_exception</code></td>
- <td align="left">Invoke a function which is undefined. Compilers will
- include this function if and only if there is a possibility of a
- runtime error. Conversely, This will create a compile time error
- if there is any possibility that the operation will fail at
- runtime. Use the action to guarantee that your application will
- never produce an invalid result. Any operation invoke</td>
- </tr>
- </tbody>
- </table></div>
- <p>But of course one is free to provide his own. Here is an example of
- a function object which would could be used exception conditions.</p>
- <pre class="programlisting"><span class="comment">// log an exception condition but continue processing as though nothing has happened</span>
- <span class="comment">// this would emulate the behavior of an unsafe type.</span>
- <span class="keyword">struct</span> <span class="identifier">log_runtime_exception</span> <span class="special">{</span>
- <span class="identifier">log_runtime_exception</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">safe_numerics_error</span> <span class="special">&</span> <span class="identifier">e</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span> <span class="identifier">message</span><span class="special">)</span><span class="special">{</span>
- <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Caught system_error with code "</span> <span class="special"><<</span> <span class="identifier">e</span><span class="special">.</span><span class="identifier">code</span><span class="special">(</span><span class="special">)</span>
- <span class="special"><<</span> <span class="string">" meaning "</span> <span class="special"><<</span> <span class="identifier">e</span><span class="special">.</span><span class="identifier">what</span><span class="special">(</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span>
- <span class="special">}</span>
- <span class="special">}</span><span class="special">;</span>
- </pre>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h4 class="title">
- <a name="idm130202892272"></a>Policies Provided by the library</h4></div></div></div>
- <p>The above function object can be composed into an exception policy
- by this class. The library provides common policies all ready to use. In
- the table below, the word "loose" is used to indicate that implementation
- defined and undefined behavior is not considered an exceptional condition,
- while "strict" means the opposite. The word "exception" means that a
- runtime exception will be thrown. The word "trap" means that the mere
- possibility of an error condition will result in a compile time
- error.</p>
- <div class="informaltable"><table class="table">
- <colgroup>
- <col align="left">
- <col align="left">
- </colgroup>
- <thead><tr>
- <th align="left">Name</th>
- <th align="left">Description</th>
- </tr></thead>
- <tbody>
- <tr>
- <td align="left">
- <a name="safe_numerics.exception_policies.loose_exception_policy"></a><a class="link" href="exception_policies.html#safe_numerics.exception_policies.loose_exception_policy">loose_exception_policy</a>
- </td>
- <td align="left">Throws runtime exception on any arithmetic error.
- Undefined and implementation defined behavior is permitted as
- long as it does not produce an arithmetic error.</td>
- </tr>
- <tr>
- <td align="left">
- <a name="safe_numerics.exception_policies.loose_trap_policy"></a><code class="computeroutput"><a class="link" href="exception_policies.html#safe_numerics.exception_policies.loose_trap_policy">loose_trap_policy</a></code>
- </td>
- <td align="left">Invoke a compile time error in any case where it's
- possible to result in an arithmetic error.</td>
- </tr>
- <tr>
- <td align="left">
- <a name="safe_numerics.exception_policies.strict_exception_policy"></a><code class="computeroutput"><a class="link" href="exception_policies.html#safe_numerics.exception_policies.strict_exception_policy">strict_exception_policy</a></code>
- </td>
- <td align="left">Throws runtime exception on any arithmetic error. Any
- undefined or implementation defined behavior also results in
- throwing an exception.</td>
- </tr>
- <tr>
- <td align="left">
- <a name="safe_numerics.exception_policies.strict_trap_policy"></a><code class="computeroutput"><a class="link" href="exception_policies.html#safe_numerics.exception_policies.strict_trap_policy">strict_trap_policy</a></code>
- </td>
- <td align="left">Invoke a compile time error in any case where it's
- possible to result in an arithmetic error, undefined behavior or
- implementation defined behavior</td>
- </tr>
- <tr>
- <td align="left">
- <a name="safe_numerics.exception_policies.default_exception_policy"></a><code class="computeroutput"><a class="link" href="exception_policies.html#safe_numerics.exception_policies.default_exception_policy">default_exception_policy</a></code>
- </td>
- <td align="left">an alias for <code class="computeroutput"><a class="link" href="exception_policies.html#safe_numerics.exception_policies.strict_exception_policy">strict_exception_policy</a></code>
- </td>
- </tr>
- </tbody>
- </table></div>
- <p>If none of the above suit your needs, you're free to
- create your own. Here is one where use the logging function object defined
- above as a component in a loose exception policy which logs any arithmetic
- errors and ignores any other types of errors.</p>
- <pre class="programlisting"><span class="comment">// logging policy</span>
- <span class="comment">// log arithmetic errors but ignore them and continue to execute</span>
- <span class="comment">// implementation defined and undefined behavior is just executed</span>
- <span class="comment">// without logging.</span>
- <span class="keyword">using</span> <span class="identifier">logging_exception_policy</span> <span class="special">=</span> <span class="identifier">exception_policy</span><span class="special"><</span>
- <span class="identifier">log_runtime_exception</span><span class="special">,</span> <span class="comment">// arithmetic error</span>
- <span class="identifier">ignore_exception</span><span class="special">,</span> <span class="comment">// implementation defined behavior</span>
- <span class="identifier">ignore_exception</span><span class="special">,</span> <span class="comment">// undefined behavior</span>
- <span class="identifier">ignore_exception</span> <span class="comment">// uninitialized value</span>
- <span class="special">></span><span class="special">;</span>
- </pre>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h4 class="title">
- <a name="idm130202855952"></a>Header</h4></div></div></div>
- <p><a href="../../include/concept/exception_policy.hpp" target="_top"><code class="computeroutput">#include
- <boost/numeric/safe_numerics/concept/exception_policy.hpp></code></a></p>
- </div>
- </div>
- <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
- <td align="left"></td>
- <td align="right"><div class="copyright-footer">Copyright © 2012-2018 Robert Ramey<p><a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">Subject to Boost
- Software License</a></p>
- </div></td>
- </tr></table>
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