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<div class="titlepage"><div><div><h4 class="title">
<a name="math_toolkit.policy.pol_ref.policy_defaults"></a><a class="link" href="policy_defaults.html" title="Using macros to Change the Policy Defaults"> Using
macros to Change the Policy Defaults</a>
</h4></div></div></div>
<p>
You can use the various macros below to change any (or all) of the policies.
</p>
<p>
You can make a local change by placing a macro definition <span class="bold"><strong>before</strong></span>
a function or distribution #include.
</p>
<div class="caution"><table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../../../../../../doc/src/images/caution.png"></td>
<th align="left">Caution</th>
</tr>
<tr><td align="left" valign="top"><p>
There is a danger of One-Definition-Rule violations if you add ad-hoc
macros to more than one source files: these must be set the same in
<span class="bold"><strong>every translation unit</strong></span>.
</p></td></tr>
</table></div>
<div class="caution"><table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../../../../../../doc/src/images/caution.png"></td>
<th align="left">Caution</th>
</tr>
<tr><td align="left" valign="top"><p>
If you place it after the #include it will have no effect, (and it will
affect only any other following #includes). This is probably not what
you intend!
</p></td></tr>
</table></div>
<p>
If you want to alter the defaults for any or all of the policies for <span class="bold"><strong>all</strong></span> functions and distributions, installation-wide,
then you can do so by defining various macros in <a href="../../../../../../../../boost/math/tools/user.hpp" target="_top">boost/math/tools/user.hpp</a>.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_domain_error_policy"></a><h6>
<a name="id1270171"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_domain_error_policy">BOOST_MATH_DOMAIN_ERROR_POLICY</a>
</h6>
<p>
Defines what happens when a domain error occurs, if not defined then defaults
to <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, but
can be set to any of the enumerated actions for error handing: <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, <code class="computeroutput"><span class="identifier">errno_on_error</span></code>,
<code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_pole_error_policy"></a><h6>
<a name="id1270224"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_pole_error_policy">BOOST_MATH_POLE_ERROR_POLICY</a>
</h6>
<p>
Defines what happens when a pole error occurs, if not defined then defaults
to <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, but
can be set to any of the enumerated actions for error handing: <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, <code class="computeroutput"><span class="identifier">errno_on_error</span></code>,
<code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_overflow_error_policy"></a><h6>
<a name="id1270277"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_overflow_error_policy">BOOST_MATH_OVERFLOW_ERROR_POLICY</a>
</h6>
<p>
Defines what happens when an overflow error occurs, if not defined then
defaults to <code class="computeroutput"><span class="identifier">throw_on_error</span></code>,
but can be set to any of the enumerated actions for error handing: <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, <code class="computeroutput"><span class="identifier">errno_on_error</span></code>,
<code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_rounding_error_policy"></a><h6>
<a name="id1270330"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_rounding_error_policy">BOOST_MATH_ROUNDING_ERROR_POLICY</a>
</h6>
<p>
Defines what happens when a rounding error occurs, if not defined then
defaults to <code class="computeroutput"><span class="identifier">throw_on_error</span></code>,
but can be set to any of the enumerated actions for error handing: <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, <code class="computeroutput"><span class="identifier">errno_on_error</span></code>,
<code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_evaluation_error_policy"></a><h6>
<a name="id1270382"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_evaluation_error_policy">BOOST_MATH_EVALUATION_ERROR_POLICY</a>
</h6>
<p>
Defines what happens when an internal evaluation error occurs, if not defined
then defaults to <code class="computeroutput"><span class="identifier">throw_on_error</span></code>,
but can be set to any of the enumerated actions for error handing: <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, <code class="computeroutput"><span class="identifier">errno_on_error</span></code>,
<code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_underflow_error_policy"></a><h6>
<a name="id1270435"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_underflow_error_policy">BOOST_MATH_UNDERFLOW_ERROR_POLICY</a>
</h6>
<p>
Defines what happens when an overflow error occurs, if not defined then
defaults to <code class="computeroutput"><span class="identifier">ignore_error</span></code>,
but can be set to any of the enumerated actions for error handing: <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, <code class="computeroutput"><span class="identifier">errno_on_error</span></code>,
<code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_denorm_error_policy"></a><h6>
<a name="id1270488"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_denorm_error_policy">BOOST_MATH_DENORM_ERROR_POLICY</a>
</h6>
<p>
Defines what happens when a denormalisation error occurs, if not defined
then defaults to <code class="computeroutput"><span class="identifier">ignore_error</span></code>,
but can be set to any of the enumerated actions for error handing: <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, <code class="computeroutput"><span class="identifier">errno_on_error</span></code>,
<code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_indeterminate_result_error_policy"></a><h6>
<a name="id1270541"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_indeterminate_result_error_policy">BOOST_MATH_INDETERMINATE_RESULT_ERROR_POLICY</a>
</h6>
<p>
Defines what happens when the result is indeterminate, but where there
is none the less a convention for the result. If not defined then defaults
to <code class="computeroutput"><span class="identifier">ignore_error</span></code>, but can
be set to any of the enumerated actions for error handing: <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, <code class="computeroutput"><span class="identifier">errno_on_error</span></code>,
<code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_digits10_policy"></a><h6>
<a name="id1270594"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_digits10_policy">BOOST_MATH_DIGITS10_POLICY</a>
</h6>
<p>
Defines how many decimal digits to use in internal computations: defaults
to <code class="computeroutput"><span class="number">0</span></code> - meaning use all available
digits - but can be set to some other decimal value. Since setting this
is likely to have a substantial impact on accuracy, it's not generally
recommended that you change this from the default.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_promote_float_policy"></a><h6>
<a name="id1270618"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_promote_float_policy">BOOST_MATH_PROMOTE_FLOAT_POLICY</a>
</h6>
<p>
Determines whether <code class="computeroutput"><span class="keyword">float</span></code> types
get promoted to <code class="computeroutput"><span class="keyword">double</span></code> internally
to ensure maximum precision in the result, defaults to <code class="computeroutput"><span class="keyword">true</span></code>,
but can be set to <code class="computeroutput"><span class="keyword">false</span></code> to
turn promotion of <code class="computeroutput"><span class="keyword">float</span></code>'s
off.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_promote_double_policy"></a><h6>
<a name="id1270670"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_promote_double_policy">BOOST_MATH_PROMOTE_DOUBLE_POLICY</a>
</h6>
<p>
Determines whether <code class="computeroutput"><span class="keyword">double</span></code>
types get promoted to <code class="computeroutput"><span class="keyword">long</span> <span class="keyword">double</span></code> internally to ensure maximum precision
in the result, defaults to <code class="computeroutput"><span class="keyword">true</span></code>,
but can be set to <code class="computeroutput"><span class="keyword">false</span></code> to
turn promotion of <code class="computeroutput"><span class="keyword">double</span></code>'s
off.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_discrete_quantile_policy"></a><h6>
<a name="id1270728"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_discrete_quantile_policy">BOOST_MATH_DISCRETE_QUANTILE_POLICY</a>
</h6>
<p>
Determines how discrete quantiles return their results: either as an integer,
or as a real value, can be set to one of the enumerated values: <code class="computeroutput"><span class="identifier">real</span></code>, <code class="computeroutput"><span class="identifier">integer_round_outwards</span></code>,
<code class="computeroutput"><span class="identifier">integer_round_inwards</span></code>,
<code class="computeroutput"><span class="identifier">integer_round_down</span></code>, <code class="computeroutput"><span class="identifier">integer_round_up</span></code>, <code class="computeroutput"><span class="identifier">integer_round_nearest</span></code>.
Defaults to <code class="computeroutput"><span class="identifier">integer_round_outwards</span></code>.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_assert_undefined_policy"></a><h6>
<a name="id1270795"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_assert_undefined_policy">BOOST_MATH_ASSERT_UNDEFINED_POLICY</a>
</h6>
<p>
Determines whether functions that are mathematically undefined for a specific
distribution compile or raise a static (i.e. compile-time) assertion. Defaults
to <code class="computeroutput"><span class="keyword">true</span></code>: meaning that any
mathematically undefined function will not compile. When set to <code class="computeroutput"><span class="keyword">false</span></code> then the function will compile but
return the result of a domain error: this can be useful for some generic
code, that needs to work with all distributions and determine at runtime
whether or not a particular property is well defined.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_max_series_iteration_policy"></a><h6>
<a name="id1270826"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_max_series_iteration_policy">BOOST_MATH_MAX_SERIES_ITERATION_POLICY</a>
</h6>
<p>
Determines how many series iterations a special function is permitted to
perform before it gives up and returns an <a class="link" href="../../main_overview/error_handling.html#evaluation_error">evaluation_error</a>:
Defaults to 1000000.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.boost_math_max_root_iteration_policy"></a><h6>
<a name="id1270848"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.boost_math_max_root_iteration_policy">BOOST_MATH_MAX_ROOT_ITERATION_POLICY</a>
</h6>
<p>
Determines how many root-finding iterations a special function is permitted
to perform before it gives up and returns an <a class="link" href="../../main_overview/error_handling.html#evaluation_error">evaluation_error</a>:
Defaults to 200.
</p>
<a name="math_toolkit.policy.pol_ref.policy_defaults.example"></a><h6>
<a name="id1270870"></a>
<a class="link" href="policy_defaults.html#math_toolkit.policy.pol_ref.policy_defaults.example">Example</a>
</h6>
<p>
Suppose we want overflow errors to set <code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code> and return an infinity, discrete
quantiles to return a real-valued result (rather than round to integer),
and for mathematically undefined functions to compile, but return a domain
error. Then we could add the following to boost/math/tools/user.hpp:
</p>
<pre class="programlisting"><span class="preprocessor">#define</span> <span class="identifier">BOOST_MATH_OVERFLOW_ERROR_POLICY</span> <span class="identifier">errno_on_error</span>
<span class="preprocessor">#define</span> <span class="identifier">BOOST_MATH_DISCRETE_QUANTILE_POLICY</span> <span class="identifier">real</span>
<span class="preprocessor">#define</span> <span class="identifier">BOOST_MATH_ASSERT_UNDEFINED_POLICY</span> <span class="keyword">false</span>
</pre>
<p>
or we could place these definitions <span class="bold"><strong>before</strong></span>
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">math</span><span class="special">/</span><span class="identifier">distributions</span><span class="special">/</span><span class="identifier">normal</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<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">normal_distribution</span><span class="special">;</span>
</pre>
<p>
in a source .cpp file.
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2006 , 2007, 2008, 2009 John Maddock, Paul A. Bristow,
Hubert Holin, Xiaogang Zhang, Bruno Lalande, Johan Råde, Gautam Sewani
and Thijs van den Berg<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>)
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