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1129 lines
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
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<title>Error Handling</title>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="math_toolkit.error_handling"></a><a class="link" href="error_handling.html" title="Error Handling">Error Handling</a>
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</h2></div></div></div>
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<h4>
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<a name="math_toolkit.error_handling.h0"></a>
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<span class="phrase"><a name="math_toolkit.error_handling.quick_reference"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.quick_reference">Quick
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Reference</a>
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</h4>
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<p>
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Handling of errors by this library is split into two orthogonal parts:
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</p>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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What kind of error has been raised?
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</li>
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<li class="listitem">
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What should be done when the error is raised?
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</li>
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</ul></div>
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<div class="warning"><table border="0" summary="Warning">
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<tr>
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<td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../../doc/src/images/warning.png"></td>
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<th align="left">Warning</th>
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</tr>
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<tr><td align="left" valign="top"><p>
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The default error actions are to throw an exception with an informative error
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message. If you do not try to catch the exception, you will not see the message!
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</p></td></tr>
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</table></div>
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<p>
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The kinds of errors that can be raised are:
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</p>
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<div class="variablelist">
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<p class="title"><b></b></p>
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<dl class="variablelist">
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<dt><span class="term">Domain Error</span></dt>
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<dd><p>
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Occurs when one or more arguments to a function are out of range.
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</p></dd>
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<dt><span class="term">Pole Error</span></dt>
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<dd><p>
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Occurs when the particular arguments cause the function to be evaluated
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at a pole with no well defined residual value. For example if <a class="link" href="sf_gamma/tgamma.html" title="Gamma">tgamma</a>
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is evaluated at exactly -2, the function approaches different limiting
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values depending upon whether you approach from just above or just below
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-2. Hence the function has no well defined value at this point and a
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Pole Error will be raised.
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</p></dd>
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<dt><span class="term">Overflow Error</span></dt>
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<dd><p>
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Occurs when the result is either infinite, or too large to represent
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in the numeric type being returned by the function.
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</p></dd>
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<dt><span class="term">Underflow Error</span></dt>
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<dd><p>
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Occurs when the result is not zero, but is too small to be represented
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by any other value in the type being returned by the function.
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</p></dd>
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<dt><span class="term">Denormalisation Error</span></dt>
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<dd><p>
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Occurs when the returned result would be a denormalised value.
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</p></dd>
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<dt><span class="term">Rounding Error</span></dt>
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<dd><p>
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Occurs when the argument to one of the rounding functions <a class="link" href="rounding/trunc.html" title="Truncation Functions">trunc</a>,
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<a class="link" href="rounding/round.html" title="Rounding Functions">round</a> and <a class="link" href="rounding/modf.html" title="Integer and Fractional Part Splitting (modf)">modf</a>
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can not be represented as an integer type, is outside the range of the
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result type.
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</p></dd>
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<dt><span class="term">Evaluation Error</span></dt>
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<dd><p>
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Occurs if no method of evaluation is known, or when an internal error
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occurred that prevented the result from being evaluated: this should
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never occur, but if it does, then it's likely to be due to an iterative
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method not converging fast enough.
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</p></dd>
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<dt><span class="term">Indeterminate Result Error</span></dt>
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<dd><p>
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Occurs when the result of a function is not defined for the values that
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were passed to it.
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</p></dd>
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</dl>
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</div>
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<p>
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The action undertaken by each error condition is determined by the current
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<a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a> in effect. This can be changed program-wide
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by setting some configuration macros, or at namespace scope, or at the call
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site (by specifying a specific policy in the function call).
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</p>
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<p>
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The available actions are:
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</p>
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<div class="variablelist">
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<p class="title"><b></b></p>
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<dl class="variablelist">
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<dt><span class="term">throw_on_error</span></dt>
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<dd><p>
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Throws the exception most appropriate to the error condition.
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</p></dd>
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<dt><span class="term">errno_on_error</span></dt>
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<dd><p>
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Sets ::errno to an appropriate value, and then returns the most appropriate
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result
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</p></dd>
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<dt><span class="term">ignore_error</span></dt>
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<dd><p>
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Ignores the error and simply the returns the most appropriate result.
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</p></dd>
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<dt><span class="term">user_error</span></dt>
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<dd><p>
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Calls a <a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user-supplied
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error handler</a>.
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</p></dd>
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</dl>
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</div>
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<p>
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The following tables show all the permutations of errors and actions, with
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the <span class="bold"><strong>default action for each error shown in bold</strong></span>:
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</p>
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<div class="table">
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<a name="math_toolkit.error_handling.possible_actions_for_domain_erro"></a><p class="title"><b>Table 1.1. Possible Actions for Domain Errors</b></p>
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<div class="table-contents"><table class="table" summary="Possible Actions for Domain Errors">
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<colgroup>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>
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<p>
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Action
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</p>
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</th>
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<th>
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<p>
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Behaviour
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</p>
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</th>
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</tr></thead>
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<tbody>
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<tr>
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<td>
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<p>
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throw_on_error
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</p>
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</td>
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<td>
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<p>
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<span class="bold"><strong>Throws <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">domain_error</span></code></strong></span>
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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errno_on_error
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</p>
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</td>
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<td>
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<p>
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Sets <code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code>
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to <code class="computeroutput"><span class="identifier">EDOM</span></code> and returns
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<code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">quiet_NaN</span><span class="special">()</span></code>
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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ignore_error
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</p>
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</td>
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<td>
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<p>
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Returns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">quiet_NaN</span><span class="special">()</span></code>
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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user_error
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</p>
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</td>
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<td>
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<p>
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Returns the result of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">user_domain_error</span></code>:
|
|
<a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">this function
|
|
must be defined by the user</a>.
|
|
</p>
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</td>
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</tr>
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</tbody>
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</table></div>
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</div>
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<br class="table-break"><div class="table">
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<a name="math_toolkit.error_handling.possible_actions_for_pole_errors"></a><p class="title"><b>Table 1.2. Possible Actions for Pole Errors</b></p>
|
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<div class="table-contents"><table class="table" summary="Possible Actions for Pole Errors">
|
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<colgroup>
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|
<col>
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<col>
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|
</colgroup>
|
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<thead><tr>
|
|
<th>
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<p>
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|
Action
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|
</p>
|
|
</th>
|
|
<th>
|
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<p>
|
|
Behaviour
|
|
</p>
|
|
</th>
|
|
</tr></thead>
|
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<tbody>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
throw_on_error
|
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</p>
|
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</td>
|
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<td>
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|
<p>
|
|
<span class="bold"><strong>Throws <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">domain_error</span></code></strong></span>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
errno_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Sets <code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code>
|
|
to <code class="computeroutput"><span class="identifier">EDOM</span></code> and returns
|
|
<code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">quiet_NaN</span><span class="special">()</span></code>
|
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</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
ignore_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Returns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">quiet_NaN</span><span class="special">()</span></code>
|
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</p>
|
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</td>
|
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</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
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user_error
|
|
</p>
|
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</td>
|
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<td>
|
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<p>
|
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Returns the result of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">user_pole_error</span></code>:
|
|
<a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">this function
|
|
must be defined by the user</a>.
|
|
</p>
|
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</td>
|
|
</tr>
|
|
</tbody>
|
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</table></div>
|
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</div>
|
|
<br class="table-break"><div class="table">
|
|
<a name="math_toolkit.error_handling.possible_actions_for_overflow_er"></a><p class="title"><b>Table 1.3. Possible Actions for Overflow Errors</b></p>
|
|
<div class="table-contents"><table class="table" summary="Possible Actions for Overflow Errors">
|
|
<colgroup>
|
|
<col>
|
|
<col>
|
|
</colgroup>
|
|
<thead><tr>
|
|
<th>
|
|
<p>
|
|
Action
|
|
</p>
|
|
</th>
|
|
<th>
|
|
<p>
|
|
Behaviour
|
|
</p>
|
|
</th>
|
|
</tr></thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
throw_on_error
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</p>
|
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</td>
|
|
<td>
|
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<p>
|
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<span class="bold"><strong>Throws <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">overflow_error</span></code></strong></span>
|
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</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
errno_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Sets <code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code>
|
|
to <code class="computeroutput"><span class="identifier">ERANGE</span></code> and returns
|
|
<code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">infinity</span><span class="special">()</span></code>
|
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</p>
|
|
</td>
|
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</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
ignore_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Returns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">infinity</span><span class="special">()</span></code>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
user_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Returns the result of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">user_overflow_error</span></code>:
|
|
<a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">this function
|
|
must be defined by the user</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table></div>
|
|
</div>
|
|
<br class="table-break"><div class="table">
|
|
<a name="math_toolkit.error_handling.possible_actions_for_underflow_e"></a><p class="title"><b>Table 1.4. Possible Actions for Underflow Errors</b></p>
|
|
<div class="table-contents"><table class="table" summary="Possible Actions for Underflow Errors">
|
|
<colgroup>
|
|
<col>
|
|
<col>
|
|
</colgroup>
|
|
<thead><tr>
|
|
<th>
|
|
<p>
|
|
Action
|
|
</p>
|
|
</th>
|
|
<th>
|
|
<p>
|
|
Behaviour
|
|
</p>
|
|
</th>
|
|
</tr></thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
throw_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Throws <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">underflow_error</span></code>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
errno_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Sets <code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code>
|
|
to <code class="computeroutput"><span class="identifier">ERANGE</span></code> and returns
|
|
0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
ignore_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
<span class="bold"><strong>Returns 0</strong></span>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
user_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Returns the result of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">user_underflow_error</span></code>:
|
|
<a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">this function
|
|
must be defined by the user</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table></div>
|
|
</div>
|
|
<br class="table-break"><div class="table">
|
|
<a name="math_toolkit.error_handling.possible_actions_for_denorm_erro"></a><p class="title"><b>Table 1.5. Possible Actions for Denorm Errors</b></p>
|
|
<div class="table-contents"><table class="table" summary="Possible Actions for Denorm Errors">
|
|
<colgroup>
|
|
<col>
|
|
<col>
|
|
</colgroup>
|
|
<thead><tr>
|
|
<th>
|
|
<p>
|
|
Action
|
|
</p>
|
|
</th>
|
|
<th>
|
|
<p>
|
|
Behaviour
|
|
</p>
|
|
</th>
|
|
</tr></thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
throw_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Throws <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">underflow_error</span></code>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
errno_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Sets <code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code>
|
|
to <code class="computeroutput"><span class="identifier">ERANGE</span></code> and returns
|
|
the denormalised value.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
ignore_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
<span class="bold"><strong>Returns the denormalised value.</strong></span>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
user_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Returns the result of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">user_denorm_error</span></code>:
|
|
<a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">this function
|
|
must be defined by the user</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table></div>
|
|
</div>
|
|
<br class="table-break"><div class="table">
|
|
<a name="math_toolkit.error_handling.possible_actions_for_rounding_er"></a><p class="title"><b>Table 1.6. Possible Actions for Rounding Errors</b></p>
|
|
<div class="table-contents"><table class="table" summary="Possible Actions for Rounding Errors">
|
|
<colgroup>
|
|
<col>
|
|
<col>
|
|
</colgroup>
|
|
<thead><tr>
|
|
<th>
|
|
<p>
|
|
Action
|
|
</p>
|
|
</th>
|
|
<th>
|
|
<p>
|
|
Behaviour
|
|
</p>
|
|
</th>
|
|
</tr></thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
throw_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Throws <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">rounding_error</span></code>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
errno_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Sets <code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code>
|
|
to <code class="computeroutput"><span class="identifier">ERANGE</span></code> and returns
|
|
the largest representable value of the target integer type (or the
|
|
most negative value if the argument to the function was less than
|
|
zero).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
ignore_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
<span class="bold"><strong>Returns the largest representable value of
|
|
the target integer type (or the most negative value if the argument
|
|
to the function was less than zero).</strong></span>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
user_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Returns the result of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">user_rounding_error</span></code>:
|
|
<a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">this function
|
|
must be defined by the user</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table></div>
|
|
</div>
|
|
<br class="table-break"><div class="table">
|
|
<a name="math_toolkit.error_handling.possible_actions_for_internal_ev"></a><p class="title"><b>Table 1.7. Possible Actions for Internal Evaluation Errors</b></p>
|
|
<div class="table-contents"><table class="table" summary="Possible Actions for Internal Evaluation Errors">
|
|
<colgroup>
|
|
<col>
|
|
<col>
|
|
</colgroup>
|
|
<thead><tr>
|
|
<th>
|
|
<p>
|
|
Action
|
|
</p>
|
|
</th>
|
|
<th>
|
|
<p>
|
|
Behaviour
|
|
</p>
|
|
</th>
|
|
</tr></thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
throw_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
<span class="bold"><strong>Throws <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">evaluation_error</span></code></strong></span>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
errno_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Sets <code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code>
|
|
to <code class="computeroutput"><span class="identifier">EDOM</span></code> and returns
|
|
the closest approximation found.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
ignore_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Returns the closest approximation found.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
user_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Returns the result of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">user_evaluation_error</span></code>:
|
|
<a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">this function
|
|
must be defined by the user</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table></div>
|
|
</div>
|
|
<br class="table-break"><div class="table">
|
|
<a name="math_toolkit.error_handling.possible_actions_for_indetermina"></a><p class="title"><b>Table 1.8. Possible Actions for Indeterminate Result Errors</b></p>
|
|
<div class="table-contents"><table class="table" summary="Possible Actions for Indeterminate Result Errors">
|
|
<colgroup>
|
|
<col>
|
|
<col>
|
|
</colgroup>
|
|
<thead><tr>
|
|
<th>
|
|
<p>
|
|
Action
|
|
</p>
|
|
</th>
|
|
<th>
|
|
<p>
|
|
Behaviour
|
|
</p>
|
|
</th>
|
|
</tr></thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
throw_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Throws <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">domain_error</span></code>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
errno_on_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Sets <code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code>
|
|
to <code class="computeroutput"><span class="identifier">EDOM</span></code> and returns
|
|
the same value as <code class="computeroutput"><span class="identifier">ignore_error</span></code>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
ignore_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
<span class="bold"><strong>Returns a default result that depends on the
|
|
function where the error occurred.</strong></span>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
user_error
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
Returns the result of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">user_indeterminate_result_error</span></code>:
|
|
<a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">this function
|
|
must be defined by the user</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table></div>
|
|
</div>
|
|
<br class="table-break"><p>
|
|
All these error conditions are in namespace boost::math::policies, made available,
|
|
for example, a by namespace declaration using <code class="computeroutput"><span class="keyword">namespace</span>
|
|
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">;</span></code> or individual using declarations <code class="computeroutput"><span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">overflow_error</span><span class="special">;</span></code>.
|
|
</p>
|
|
<h4>
|
|
<a name="math_toolkit.error_handling.h1"></a>
|
|
<span class="phrase"><a name="math_toolkit.error_handling.rationale"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.rationale">Rationale</a>
|
|
</h4>
|
|
<p>
|
|
The flexibility of the current implementation should be reasonably obvious:
|
|
the default behaviours were chosen based on feedback during the formal review
|
|
of this library. It was felt that:
|
|
</p>
|
|
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
|
<li class="listitem">
|
|
Genuine errors should be flagged with exceptions rather than following
|
|
C-compatible behaviour and setting <code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code>.
|
|
</li>
|
|
<li class="listitem">
|
|
Numeric underflow and denormalised results were not considered to be fatal
|
|
errors in most cases, so it was felt that these should be ignored.
|
|
</li>
|
|
<li class="listitem">
|
|
If there is more than one error, only the first detected will be reported
|
|
in the throw message.
|
|
</li>
|
|
</ul></div>
|
|
<h4>
|
|
<a name="math_toolkit.error_handling.h2"></a>
|
|
<span class="phrase"><a name="math_toolkit.error_handling.finding_more_information"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.finding_more_information">Finding
|
|
More Information</a>
|
|
</h4>
|
|
<p>
|
|
There are some pre-processor macro defines that can be used to <a class="link" href="pol_ref/policy_defaults.html" title="Using Macros to Change the Policy Defaults">change
|
|
the policy defaults</a>. See also the <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">policy section</a>.
|
|
</p>
|
|
<p>
|
|
An example is at the Policy tutorial in <a class="link" href="pol_tutorial/changing_policy_defaults.html" title="Changing the Policy Defaults">Changing
|
|
the Policy Defaults</a>.
|
|
</p>
|
|
<p>
|
|
Full source code of this typical example of passing a 'bad' argument (negative
|
|
degrees of freedom) to Student's t distribution is <a class="link" href="stat_tut/weg/error_eg.html" title="Error Handling Example">in
|
|
the error handling example</a>.
|
|
</p>
|
|
<p>
|
|
The various kind of errors are described in more detail below.
|
|
</p>
|
|
<h4>
|
|
<a name="math_toolkit.error_handling.h3"></a>
|
|
<span class="phrase"><a name="math_toolkit.error_handling.domain_error"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.domain_error">Domain
|
|
Errors</a>
|
|
</h4>
|
|
<p>
|
|
When a special function is passed an argument that is outside the range of
|
|
values for which that function is defined, then the function returns the result
|
|
of:
|
|
</p>
|
|
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">raise_domain_error</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">FunctionName</span><span class="special">,</span> <span class="identifier">Message</span><span class="special">,</span> <span class="identifier">Val</span><span class="special">,</span> <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">);</span>
|
|
</pre>
|
|
<p>
|
|
Where <code class="computeroutput"><span class="identifier">T</span></code> is the floating-point
|
|
type passed to the function, <code class="computeroutput"><span class="identifier">FunctionName</span></code>
|
|
is the name of the function, <code class="computeroutput"><span class="identifier">Message</span></code>
|
|
is an error message describing the problem, Val is the value that was out of
|
|
range, and <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a> is the current policy in use
|
|
for the function that was called.
|
|
</p>
|
|
<p>
|
|
The default policy behaviour of this function is to throw a std::domain_error
|
|
C++ exception. But if the <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a> is to ignore
|
|
the error, or set global <code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code>,
|
|
then a NaN will be returned.
|
|
</p>
|
|
<p>
|
|
This behaviour is chosen to assist compatibility with the behaviour of <span class="emphasis"><em>ISO/IEC
|
|
9899:1999 Programming languages - C</em></span> and with the <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf" target="_top">Draft
|
|
Technical Report on C++ Library Extensions, 2005-06-24, section 5.2.1, paragraph
|
|
6</a>:
|
|
</p>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<span class="emphasis"><em>"Each of the functions declared above shall return a NaN (Not
|
|
a Number) if any argument value is a NaN, but it shall not report a domain
|
|
error. Otherwise, each of the functions declared above shall report a domain
|
|
error for just those argument values for which:</em></span>
|
|
</p></blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote">
|
|
<p>
|
|
<span class="emphasis"><em>"the function description's Returns clause explicitly specifies
|
|
a domain, and those arguments fall outside the specified domain; or</em></span>
|
|
</p>
|
|
<p>
|
|
<span class="emphasis"><em>"the corresponding mathematical function value has a non-zero
|
|
imaginary component; or</em></span>
|
|
</p>
|
|
<p>
|
|
<span class="emphasis"><em>"the corresponding mathematical function is not mathematically
|
|
defined.</em></span>
|
|
</p>
|
|
</blockquote></div>
|
|
<div class="blockquote"><blockquote class="blockquote"><p>
|
|
<span class="emphasis"><em>"Note 2: A mathematical function is mathematically defined
|
|
for a given set of argument values if it is explicitly defined for that set
|
|
of argument values or if its limiting value exists and does not depend on
|
|
the direction of approach."</em></span>
|
|
</p></blockquote></div>
|
|
<p>
|
|
Note that in order to support information-rich error messages when throwing
|
|
exceptions, <code class="computeroutput"><span class="identifier">Message</span></code> must contain
|
|
a <a href="../../../../format/index.html" target="_top">Boost.Format</a> recognised format
|
|
specifier: the argument <code class="computeroutput"><span class="identifier">Val</span></code>
|
|
is inserted into the error message according to the specifier used.
|
|
</p>
|
|
<p>
|
|
For example if <code class="computeroutput"><span class="identifier">Message</span></code> contains
|
|
a "%1%" then it is replaced by the value of <code class="computeroutput"><span class="identifier">Val</span></code>
|
|
to the full precision of T, where as "%.3g" would contain the value
|
|
of <code class="computeroutput"><span class="identifier">Val</span></code> to 3 digits. See the
|
|
<a href="../../../../format/index.html" target="_top">Boost.Format</a> documentation
|
|
for more details.
|
|
</p>
|
|
<h4>
|
|
<a name="math_toolkit.error_handling.h4"></a>
|
|
<span class="phrase"><a name="math_toolkit.error_handling.pole_error"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.pole_error">Evaluation
|
|
at a pole</a>
|
|
</h4>
|
|
<p>
|
|
When a special function is passed an argument that is at a pole without a well
|
|
defined residual value, then the function returns the result of:
|
|
</p>
|
|
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">raise_pole_error</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">FunctionName</span><span class="special">,</span> <span class="identifier">Message</span><span class="special">,</span> <span class="identifier">Val</span><span class="special">,</span> <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">);</span>
|
|
</pre>
|
|
<p>
|
|
Where <code class="computeroutput"><span class="identifier">T</span></code> is the floating point
|
|
type passed to the function, <code class="computeroutput"><span class="identifier">FunctionName</span></code>
|
|
is the name of the function, <code class="computeroutput"><span class="identifier">Message</span></code>
|
|
is an error message describing the problem, <code class="computeroutput"><span class="identifier">Val</span></code>
|
|
is the value of the argument that is at a pole, and <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a>
|
|
is the current policy in use for the function that was called.
|
|
</p>
|
|
<p>
|
|
The default behaviour of this function is to throw a std::domain_error exception.
|
|
But <a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">error handling
|
|
policies</a> can be used to change this, for example to <code class="computeroutput"><span class="identifier">ignore_error</span></code>
|
|
and return NaN.
|
|
</p>
|
|
<p>
|
|
Note that in order to support information-rich error messages when throwing
|
|
exceptions, <code class="computeroutput"><span class="identifier">Message</span></code> must contain
|
|
a <a href="../../../../format/index.html" target="_top">Boost.Format</a> recognised format
|
|
specifier: the argument <code class="computeroutput"><span class="identifier">val</span></code>
|
|
is inserted into the error message according to the specifier used.
|
|
</p>
|
|
<p>
|
|
For example if <code class="computeroutput"><span class="identifier">Message</span></code> contains
|
|
a "%1%" then it is replaced by the value of <code class="computeroutput"><span class="identifier">val</span></code>
|
|
to the full precision of T, where as "%.3g" would contain the value
|
|
of <code class="computeroutput"><span class="identifier">val</span></code> to 3 digits. See the
|
|
<a href="../../../../format/index.html" target="_top">Boost.Format</a> documentation
|
|
for more details.
|
|
</p>
|
|
<h4>
|
|
<a name="math_toolkit.error_handling.h5"></a>
|
|
<span class="phrase"><a name="math_toolkit.error_handling.overflow_error"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.overflow_error">Numeric
|
|
Overflow</a>
|
|
</h4>
|
|
<p>
|
|
When the result of a special function is too large to fit in the argument floating-point
|
|
type, then the function returns the result of:
|
|
</p>
|
|
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">raise_overflow_error</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">FunctionName</span><span class="special">,</span> <span class="identifier">Message</span><span class="special">,</span> <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">);</span>
|
|
</pre>
|
|
<p>
|
|
Where <code class="computeroutput"><span class="identifier">T</span></code> is the floating-point
|
|
type passed to the function, <code class="computeroutput"><span class="identifier">FunctionName</span></code>
|
|
is the name of the function, <code class="computeroutput"><span class="identifier">Message</span></code>
|
|
is an error message describing the problem, and <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a>
|
|
is the current policy in use for the function that was called.
|
|
</p>
|
|
<p>
|
|
The default policy for this function is that <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">overflow_error</span></code>
|
|
C++ exception is thrown. But if, for example, an <code class="computeroutput"><span class="identifier">ignore_error</span></code>
|
|
policy is used, then returns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">infinity</span><span class="special">()</span></code>.
|
|
In this situation if the type <code class="computeroutput"><span class="identifier">T</span></code>
|
|
doesn't support infinities, the maximum value for the type is returned.
|
|
</p>
|
|
<h4>
|
|
<a name="math_toolkit.error_handling.h6"></a>
|
|
<span class="phrase"><a name="math_toolkit.error_handling.underflow_error"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.underflow_error">Numeric
|
|
Underflow</a>
|
|
</h4>
|
|
<p>
|
|
If the result of a special function is known to be non-zero, but the calculated
|
|
result underflows to zero, then the function returns the result of:
|
|
</p>
|
|
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">raise_underflow_error</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">FunctionName</span><span class="special">,</span> <span class="identifier">Message</span><span class="special">,</span> <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">);</span>
|
|
</pre>
|
|
<p>
|
|
Where <code class="computeroutput"><span class="identifier">T</span></code> is the floating point
|
|
type passed to the function, <code class="computeroutput"><span class="identifier">FunctionName</span></code>
|
|
is the name of the function, <code class="computeroutput"><span class="identifier">Message</span></code>
|
|
is an error message describing the problem, and <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a>
|
|
is the current policy in use for the called function.
|
|
</p>
|
|
<p>
|
|
The default version of this function returns zero. But with another policy,
|
|
like <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, throws
|
|
an <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">underflow_error</span></code> C++ exception.
|
|
</p>
|
|
<h4>
|
|
<a name="math_toolkit.error_handling.h7"></a>
|
|
<span class="phrase"><a name="math_toolkit.error_handling.denorm_error"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.denorm_error">Denormalisation
|
|
Errors</a>
|
|
</h4>
|
|
<p>
|
|
If the result of a special function is a denormalised value <span class="emphasis"><em>z</em></span>
|
|
then the function returns the result of:
|
|
</p>
|
|
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">raise_denorm_error</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">z</span><span class="special">,</span> <span class="identifier">FunctionName</span><span class="special">,</span> <span class="identifier">Message</span><span class="special">,</span> <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">);</span>
|
|
</pre>
|
|
<p>
|
|
Where <code class="computeroutput"><span class="identifier">T</span></code> is the floating point
|
|
type passed to the function, <code class="computeroutput"><span class="identifier">FunctionName</span></code>
|
|
is the name of the function, <code class="computeroutput"><span class="identifier">Message</span></code>
|
|
is an error message describing the problem, and <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a>
|
|
is the current policy in use for the called function.
|
|
</p>
|
|
<p>
|
|
The default version of this function returns <span class="emphasis"><em>z</em></span>. But with
|
|
another policy, like <code class="computeroutput"><span class="identifier">throw_on_error</span></code>
|
|
throws an <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">underflow_error</span></code> C++ exception.
|
|
</p>
|
|
<h4>
|
|
<a name="math_toolkit.error_handling.h8"></a>
|
|
<span class="phrase"><a name="math_toolkit.error_handling.evaluation_error"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.evaluation_error">Evaluation
|
|
Errors</a>
|
|
</h4>
|
|
<p>
|
|
When a special function calculates a result that is known to be erroneous,
|
|
or where the result is incalculable then it calls:
|
|
</p>
|
|
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">raise_evaluation_error</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">FunctionName</span><span class="special">,</span> <span class="identifier">Message</span><span class="special">,</span> <span class="identifier">Val</span><span class="special">,</span> <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">);</span>
|
|
</pre>
|
|
<p>
|
|
Where <code class="computeroutput"><span class="identifier">T</span></code> is the floating point
|
|
type passed to the function, <code class="computeroutput"><span class="identifier">FunctionName</span></code>
|
|
is the name of the function, <code class="computeroutput"><span class="identifier">Message</span></code>
|
|
is an error message describing the problem, <code class="computeroutput"><span class="identifier">Val</span></code>
|
|
is the erroneous value, and <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a> is the current
|
|
policy in use for the called function.
|
|
</p>
|
|
<p>
|
|
The default behaviour of this function is to throw a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">evaluation_error</span></code>.
|
|
</p>
|
|
<p>
|
|
Note that in order to support information rich error messages when throwing
|
|
exceptions, <code class="computeroutput"><span class="identifier">Message</span></code> must contain
|
|
a <a href="../../../../format/index.html" target="_top">Boost.Format</a> recognised format
|
|
specifier: the argument <code class="computeroutput"><span class="identifier">val</span></code>
|
|
is inserted into the error message according to the specifier used.
|
|
</p>
|
|
<p>
|
|
For example if <code class="computeroutput"><span class="identifier">Message</span></code> contains
|
|
a "%1%" then it is replaced by the value of <code class="computeroutput"><span class="identifier">val</span></code>
|
|
to the full precision of T, where as "%.3g" would contain the value
|
|
of <code class="computeroutput"><span class="identifier">val</span></code> to 3 digits. See the
|
|
<a href="../../../../format/index.html" target="_top">Boost.Format</a> documentation
|
|
for more details.
|
|
</p>
|
|
<h4>
|
|
<a name="math_toolkit.error_handling.h9"></a>
|
|
<span class="phrase"><a name="math_toolkit.error_handling.indeterminate_result_error"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.indeterminate_result_error">Indeterminate
|
|
Result Errors</a>
|
|
</h4>
|
|
<p>
|
|
When the result of a special function is indeterminate for the value that was
|
|
passed to it, then the function returns the result of:
|
|
</p>
|
|
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">raise_overflow_error</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">FunctionName</span><span class="special">,</span> <span class="identifier">Message</span><span class="special">,</span> <span class="identifier">Val</span><span class="special">,</span> <span class="identifier">Default</span><span class="special">,</span> <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">);</span>
|
|
</pre>
|
|
<p>
|
|
Where <code class="computeroutput"><span class="identifier">T</span></code> is the floating-point
|
|
type passed to the function, <code class="computeroutput"><span class="identifier">FunctionName</span></code>
|
|
is the name of the function, <code class="computeroutput"><span class="identifier">Message</span></code>
|
|
is an error message describing the problem, Val is the value for which the
|
|
result is indeterminate, Default is an alternative default result that must
|
|
be returned for <code class="computeroutput"><span class="identifier">ignore_error</span></code>
|
|
and <code class="computeroutput"><span class="identifier">errno_on_erro</span></code> policies,
|
|
and <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a> is the current policy in use for the
|
|
function that was called.
|
|
</p>
|
|
<p>
|
|
The default policy for this function is <code class="computeroutput"><span class="identifier">ignore_error</span></code>:
|
|
note that this error type is reserved for situations where the result is mathematically
|
|
undefined or indeterminate, but there is none the less a convention for what
|
|
the result should be: for example the C99 standard specifies that the result
|
|
of 0<sup>0</sup> is 1, even though the result is actually mathematically indeterminate.
|
|
</p>
|
|
<h4>
|
|
<a name="math_toolkit.error_handling.h10"></a>
|
|
<span class="phrase"><a name="math_toolkit.error_handling.rounding_error"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.rounding_error">Rounding
|
|
Errors</a>
|
|
</h4>
|
|
<p>
|
|
When one of the rounding functions <a class="link" href="rounding/round.html" title="Rounding Functions">round</a>,
|
|
<a class="link" href="rounding/trunc.html" title="Truncation Functions">trunc</a> or <a class="link" href="rounding/modf.html" title="Integer and Fractional Part Splitting (modf)">modf</a>
|
|
is called with an argument that has no integer representation, or is too large
|
|
to be represented in the result type then the value returned is the result
|
|
of a call to:
|
|
</p>
|
|
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">policies</span><span class="special">::</span><span class="identifier">raise_rounding_error</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">FunctionName</span><span class="special">,</span> <span class="identifier">Message</span><span class="special">,</span> <span class="identifier">Val</span><span class="special">,</span> <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">);</span>
|
|
</pre>
|
|
<p>
|
|
Where <code class="computeroutput"><span class="identifier">T</span></code> is the floating point
|
|
type passed to the function, <code class="computeroutput"><span class="identifier">FunctionName</span></code>
|
|
is the name of the function, <code class="computeroutput"><span class="identifier">Message</span></code>
|
|
is an error message describing the problem, <code class="computeroutput"><span class="identifier">Val</span></code>
|
|
is the erroneous argument, and <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a> is the
|
|
current policy in use for the called function.
|
|
</p>
|
|
<p>
|
|
The default behaviour of this function is to throw a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">rounding_error</span></code>.
|
|
</p>
|
|
<p>
|
|
Note that in order to support information rich error messages when throwing
|
|
exceptions, <code class="computeroutput"><span class="identifier">Message</span></code> must contain
|
|
a <a href="../../../../format/index.html" target="_top">Boost.Format</a> recognised format
|
|
specifier: the argument <code class="computeroutput"><span class="identifier">val</span></code>
|
|
is inserted into the error message according to the specifier used.
|
|
</p>
|
|
<p>
|
|
For example if <code class="computeroutput"><span class="identifier">Message</span></code> contains
|
|
a "%1%" then it is replaced by the value of <code class="computeroutput"><span class="identifier">val</span></code>
|
|
to the full precision of T, where as "%.3g" would contain the value
|
|
of <code class="computeroutput"><span class="identifier">val</span></code> to 3 digits. See the
|
|
<a href="../../../../format/index.html" target="_top">Boost.Format</a> documentation
|
|
for more details.
|
|
</p>
|
|
<h4>
|
|
<a name="math_toolkit.error_handling.h11"></a>
|
|
<span class="phrase"><a name="math_toolkit.error_handling.checked_narrowing_cast"></a></span><a class="link" href="error_handling.html#math_toolkit.error_handling.checked_narrowing_cast">Errors
|
|
from typecasts</a>
|
|
</h4>
|
|
<p>
|
|
Many special functions evaluate their results at a higher precision than their
|
|
arguments in order to ensure full machine precision in the result: for example,
|
|
a function passed a float argument may evaluate its result using double precision
|
|
internally. Many of the errors listed above may therefore occur not during
|
|
evaluation, but when converting the result to the narrower result type. The
|
|
function:
|
|
</p>
|
|
<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span>
|
|
<span class="identifier">T</span> <span class="identifier">checked_narrowing_cast</span><span class="special">(</span><span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">val</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">function</span><span class="special">);</span>
|
|
</pre>
|
|
<p>
|
|
Is used to perform these conversions, and will call the error handlers listed
|
|
above on <a class="link" href="error_handling.html#math_toolkit.error_handling.overflow_error">overflow</a>,
|
|
<a class="link" href="error_handling.html#math_toolkit.error_handling.underflow_error">underflow</a>
|
|
or <a class="link" href="error_handling.html#math_toolkit.error_handling.denorm_error">denormalisation</a>.
|
|
</p>
|
|
</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 © 2006-2010, 2012-2014 Nikhar Agrawal,
|
|
Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
|
|
Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan Råde, Gautam Sewani,
|
|
Benjamin Sobotta, Thijs van den Berg, Daryle Walker and Xiaogang Zhang<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>
|
|
<hr>
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<a accesskey="p" href="result_type.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../overview.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="compilers_overview.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
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