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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="math_toolkit.pol_ref.policy_defaults"></a><a class="link" href="policy_defaults.html" title="Using Macros to Change the Policy Defaults">Using Macros to
  28       Change the Policy Defaults</a>
  29 </h3></div></div></div>
  30 <p>
  31         You can use the various macros below to change any (or all) of the policies.
  32       </p>
  33 <p>
  34         You can make a local change by placing a macro definition <span class="bold"><strong>before</strong></span>
  35         a function or distribution #include.
  36       </p>
  37 <div class="caution"><table border="0" summary="Caution">
  38 <tr>
  39 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../../../../doc/src/images/caution.png"></td>
  40 <th align="left">Caution</th>
  41 </tr>
  42 <tr><td align="left" valign="top"><p>
  43           There is a danger of One-Definition-Rule violations if you add ad-hoc macros
  44           to more than one source files: these must be set the same in <span class="bold"><strong>every translation unit</strong></span>.
  45         </p></td></tr>
  46 </table></div>
  47 <div class="caution"><table border="0" summary="Caution">
  48 <tr>
  49 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../../../../doc/src/images/caution.png"></td>
  50 <th align="left">Caution</th>
  51 </tr>
  52 <tr><td align="left" valign="top"><p>
  53           If you place it after the #include it will have no effect, (and it will
  54           affect only any other following #includes). This is probably not what you
  55           intend!
  56         </p></td></tr>
  57 </table></div>
  58 <p>
  59         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,
  60         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>.
  61       </p>
  62 <h6>
  63 <a name="math_toolkit.pol_ref.policy_defaults.h0"></a>
  64         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_domain_error_policy"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_domain_error_policy">BOOST_MATH_DOMAIN_ERROR_POLICY</a>
  65       </h6>
  66 <p>
  67         Defines what happens when a domain error occurs, if not defined then defaults
  68         to <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, but can
  69         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>,
  70         <code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
  71       </p>
  72 <h6>
  73 <a name="math_toolkit.pol_ref.policy_defaults.h1"></a>
  74         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_pole_error_policy"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_pole_error_policy">BOOST_MATH_POLE_ERROR_POLICY</a>
  75       </h6>
  76 <p>
  77         Defines what happens when a pole error occurs, if not defined then defaults
  78         to <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, but can
  79         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>,
  80         <code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
  81       </p>
  82 <h6>
  83 <a name="math_toolkit.pol_ref.policy_defaults.h2"></a>
  84         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_overflow_error_policy"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_overflow_error_policy">BOOST_MATH_OVERFLOW_ERROR_POLICY</a>
  85       </h6>
  86 <p>
  87         Defines what happens when an overflow error occurs, if not defined then defaults
  88         to <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, but can
  89         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>,
  90         <code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
  91       </p>
  92 <h6>
  93 <a name="math_toolkit.pol_ref.policy_defaults.h3"></a>
  94         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_rounding_error_policy"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_rounding_error_policy">BOOST_MATH_ROUNDING_ERROR_POLICY</a>
  95       </h6>
  96 <p>
  97         Defines what happens when a rounding error occurs, if not defined then defaults
  98         to <code class="computeroutput"><span class="identifier">throw_on_error</span></code>, but can
  99         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>,
 100         <code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
 101       </p>
 102 <h6>
 103 <a name="math_toolkit.pol_ref.policy_defaults.h4"></a>
 104         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_evaluation_error_poli"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_evaluation_error_poli">BOOST_MATH_EVALUATION_ERROR_POLICY</a>
 105       </h6>
 106 <p>
 107         Defines what happens when an internal evaluation error occurs, if not defined
 108         then defaults to <code class="computeroutput"><span class="identifier">throw_on_error</span></code>,
 109         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>,
 110         <code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
 111       </p>
 112 <h6>
 113 <a name="math_toolkit.pol_ref.policy_defaults.h5"></a>
 114         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_underflow_error_polic"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_underflow_error_polic">BOOST_MATH_UNDERFLOW_ERROR_POLICY</a>
 115       </h6>
 116 <p>
 117         Defines what happens when an overflow error occurs, if not defined then defaults
 118         to <code class="computeroutput"><span class="identifier">ignore_error</span></code>, but can
 119         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>,
 120         <code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
 121       </p>
 122 <h6>
 123 <a name="math_toolkit.pol_ref.policy_defaults.h6"></a>
 124         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_denorm_error_policy"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_denorm_error_policy">BOOST_MATH_DENORM_ERROR_POLICY</a>
 125       </h6>
 126 <p>
 127         Defines what happens when a denormalisation error occurs, if not defined
 128         then defaults to <code class="computeroutput"><span class="identifier">ignore_error</span></code>,
 129         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>,
 130         <code class="computeroutput"><span class="identifier">ignore_error</span></code> or <code class="computeroutput"><span class="identifier">user_error</span></code>.
 131       </p>
 132 <h6>
 133 <a name="math_toolkit.pol_ref.policy_defaults.h7"></a>
 134         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_indeterminate_result_"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_indeterminate_result_">BOOST_MATH_INDETERMINATE_RESULT_ERROR_POLICY</a>
 135       </h6>
 136 <p>
 137         Defines what happens when the result is indeterminate, but where there is
 138         none the less a convention for the result. If not defined then defaults to
 139         <code class="computeroutput"><span class="identifier">ignore_error</span></code>, but can be
 140         set to any of the enumerated actions for error handing: <code class="computeroutput"><span class="identifier">throw_on_error</span></code>,
 141         <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>.
 142       </p>
 143 <h6>
 144 <a name="math_toolkit.pol_ref.policy_defaults.h8"></a>
 145         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_digits10_policy"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_digits10_policy">BOOST_MATH_DIGITS10_POLICY</a>
 146       </h6>
 147 <p>
 148         Defines how many decimal digits to use in internal computations: defaults
 149         to <code class="computeroutput"><span class="number">0</span></code> - meaning use all available
 150         digits - but can be set to some other decimal value. Since setting this is
 151         likely to have a substantial impact on accuracy, it's not generally recommended
 152         that you change this from the default.
 153       </p>
 154 <h6>
 155 <a name="math_toolkit.pol_ref.policy_defaults.h9"></a>
 156         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_promote_float_policy"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_promote_float_policy">BOOST_MATH_PROMOTE_FLOAT_POLICY</a>
 157       </h6>
 158 <p>
 159         Determines whether <code class="computeroutput"><span class="keyword">float</span></code> types
 160         get promoted to <code class="computeroutput"><span class="keyword">double</span></code> internally
 161         to ensure maximum precision in the result, defaults to <code class="computeroutput"><span class="keyword">true</span></code>,
 162         but can be set to <code class="computeroutput"><span class="keyword">false</span></code> to turn
 163         promotion of <code class="computeroutput"><span class="keyword">float</span></code>'s off.
 164       </p>
 165 <h6>
 166 <a name="math_toolkit.pol_ref.policy_defaults.h10"></a>
 167         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_promote_double_policy"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_promote_double_policy">BOOST_MATH_PROMOTE_DOUBLE_POLICY</a>
 168       </h6>
 169 <p>
 170         Determines whether <code class="computeroutput"><span class="keyword">double</span></code> types
 171         get promoted to <code class="computeroutput"><span class="keyword">long</span> <span class="keyword">double</span></code>
 172         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>
 173         to turn promotion of <code class="computeroutput"><span class="keyword">double</span></code>'s
 174         off.
 175       </p>
 176 <h6>
 177 <a name="math_toolkit.pol_ref.policy_defaults.h11"></a>
 178         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_discrete_quantile_pol"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_discrete_quantile_pol">BOOST_MATH_DISCRETE_QUANTILE_POLICY</a>
 179       </h6>
 180 <p>
 181         Determines how discrete quantiles return their results: either as an integer,
 182         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>,
 183         <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>,
 184         <code class="computeroutput"><span class="identifier">integer_round_nearest</span></code>. Defaults
 185         to <code class="computeroutput"><span class="identifier">integer_round_outwards</span></code>.
 186       </p>
 187 <h6>
 188 <a name="math_toolkit.pol_ref.policy_defaults.h12"></a>
 189         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_assert_undefined_poli"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_assert_undefined_poli">BOOST_MATH_ASSERT_UNDEFINED_POLICY</a>
 190       </h6>
 191 <p>
 192         Determines whether functions that are mathematically undefined for a specific
 193         distribution compile or raise a static (i.e. compile-time) assertion. Defaults
 194         to <code class="computeroutput"><span class="keyword">true</span></code>: meaning that any mathematically
 195         undefined function will not compile. When set to <code class="computeroutput"><span class="keyword">false</span></code>
 196         then the function will compile but return the result of a domain error: this
 197         can be useful for some generic code, that needs to work with all distributions
 198         and determine at runtime whether or not a particular property is well defined.
 199       </p>
 200 <h6>
 201 <a name="math_toolkit.pol_ref.policy_defaults.h13"></a>
 202         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_max_series_iteration_"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_max_series_iteration_">BOOST_MATH_MAX_SERIES_ITERATION_POLICY</a>
 203       </h6>
 204 <p>
 205         Determines how many series iterations a special function is permitted to
 206         perform before it gives up and returns an <a class="link" href="../error_handling.html#math_toolkit.error_handling.evaluation_error">evaluation_error</a>:
 207         Defaults to 1000000.
 208       </p>
 209 <h6>
 210 <a name="math_toolkit.pol_ref.policy_defaults.h14"></a>
 211         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.boost_math_max_root_iteration_po"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.boost_math_max_root_iteration_po">BOOST_MATH_MAX_ROOT_ITERATION_POLICY</a>
 212       </h6>
 213 <p>
 214         Determines how many root-finding iterations a special function is permitted
 215         to perform before it gives up and returns an <a class="link" href="../error_handling.html#math_toolkit.error_handling.evaluation_error">evaluation_error</a>:
 216         Defaults to 200.
 217       </p>
 218 <h6>
 219 <a name="math_toolkit.pol_ref.policy_defaults.h15"></a>
 220         <span class="phrase"><a name="math_toolkit.pol_ref.policy_defaults.example"></a></span><a class="link" href="policy_defaults.html#math_toolkit.pol_ref.policy_defaults.example">Example</a>
 221       </h6>
 222 <p>
 223         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
 224         quantiles to return a real-valued result (rather than round to integer),
 225         and for mathematically undefined functions to compile, but return a domain
 226         error. Then we could add the following to boost/math/tools/user.hpp:
 227       </p>
 228 <pre class="programlisting"><span class="preprocessor">#define</span> <span class="identifier">BOOST_MATH_OVERFLOW_ERROR_POLICY</span> <span class="identifier">errno_on_error</span>
 229 <span class="preprocessor">#define</span> <span class="identifier">BOOST_MATH_DISCRETE_QUANTILE_POLICY</span> <span class="identifier">real</span>
 230 <span class="preprocessor">#define</span> <span class="identifier">BOOST_MATH_ASSERT_UNDEFINED_POLICY</span> <span class="keyword">false</span>
 231 </pre>
 232 <p>
 233         or we could place these definitions <span class="bold"><strong>before</strong></span>
 234       </p>
 235 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
 236   <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>
 237 </pre>
 238 <p>
 239         in a source .cpp file.
 240       </p>
 241 </div>
 242 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 243 <td align="left"></td>
 244 <td align="right"><div class="copyright-footer">Copyright &#169; 2006-2019 Nikhar
 245       Agrawal, Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos,
 246       Hubert Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Matthew Pulver, Johan
 247       R&#229;de, Gautam Sewani, Benjamin Sobotta, Nicholas Thompson, Thijs van den Berg,
 248       Daryle Walker and Xiaogang Zhang<p>
 249         Distributed under the Boost Software License, Version 1.0. (See accompanying
 250         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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