1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Using Macros to Change the Policy Defaults</title> 5<link rel="stylesheet" href="../../math.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../index.html" title="Math Toolkit 2.12.0"> 8<link rel="up" href="../pol_ref.html" title="Policy Reference"> 9<link rel="prev" href="iteration_pol.html" title="Iteration Limits Policies"> 10<link rel="next" href="namespace_pol.html" title="Setting Polices at Namespace Scope"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="iteration_pol.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../pol_ref.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="namespace_pol.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 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"><</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> 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 © 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 Råde, 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>) 251 </p> 252</div></td> 253</tr></table> 254<hr> 255<div class="spirit-nav"> 256<a accesskey="p" href="iteration_pol.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../pol_ref.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="namespace_pol.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 257</div> 258</body> 259</html> 260
