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<title>Policy Overview</title>
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<link rel="up" href="../policy.html" title="Chapter 22. Policies: Controlling Precision, Error Handling etc">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="math_toolkit.pol_overview"></a><a class="link" href="pol_overview.html" title="Policy Overview">Policy Overview</a>
</h2></div></div></div>
<p>
Policies are a powerful fine-grain mechanism that allow you to customise the
behaviour of this library according to your needs. There is more information
available in the <a class="link" href="pol_tutorial.html" title="Policy Tutorial">policy tutorial</a>
and the <a class="link" href="pol_ref.html" title="Policy Reference">policy reference</a>.
</p>
<p>
Generally speaking, unless you find that the <a class="link" href="pol_tutorial/policy_tut_defaults.html" title="Policies Have Sensible Defaults">default
policy behaviour</a> when encountering 'bad' argument values does not meet
your needs, you should not need to worry about policies.
</p>
<p>
Policies are a compile-time mechanism that allow you to change error-handling
or calculation precision either program wide, or at the call site.
</p>
<p>
Although the policy mechanism itself is rather complicated, in practice it
is easy to use, and very flexible.
</p>
<p>
Using policies you can control:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">How results
from 'bad' arguments are handled</a>, including those that cannot be
fully evaluated.
</li>
<li class="listitem">
How <a class="link" href="pol_ref/internal_promotion.html" title="Internal Floating-point Promotion Policies">accuracy is
controlled by internal promotion</a> to use more precise types.
</li>
<li class="listitem">
What working <a class="link" href="pol_ref/precision_pol.html" title="Precision Policies">precision</a>
should be used to calculate results.
</li>
<li class="listitem">
What to do when a <a class="link" href="pol_ref/assert_undefined.html" title="Mathematically Undefined Function Policies">mathematically
undefined function</a> is used: Should this raise a run-time or compile-time
error?
</li>
<li class="listitem">
Whether <a class="link" href="pol_ref/discrete_quant_ref.html" title="Discrete Quantile Policies">discrete
functions</a>, like the binomial, should return real or only integral
values, and how they are rounded.
</li>
<li class="listitem">
How many iterations a special function is permitted to perform in a series
evaluation or root finding algorithm before it gives up and raises an
<a class="link" href="error_handling.html#math_toolkit.error_handling.evaluation_error">evaluation_error</a>.
</li>
</ul></div>
<p>
You can control policies:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
Using <a class="link" href="pol_ref/policy_defaults.html" title="Using Macros to Change the Policy Defaults">macros</a>
to change any default policy: the is the preferred method for installation
wide policies.
</li>
<li class="listitem">
At your chosen <a class="link" href="pol_ref/namespace_pol.html" title="Setting Polices at Namespace Scope">namespace
scope</a> for distributions and/or functions: this is the preferred
method for project, namespace, or translation unit scope policies.
</li>
<li class="listitem">
In an ad-hoc manner <a class="link" href="pol_tutorial/ad_hoc_sf_policies.html" title="Changing the Policy on an Ad Hoc Basis for the Special Functions">by
passing a specific policy to a special function</a>, or to a <a class="link" href="pol_tutorial/ad_hoc_dist_policies.html" title="Setting Policies for Distributions on an Ad Hoc Basis">statistical
distribution</a>.
</li>
</ul></div>
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<div class="copyright-footer">Copyright © 2006-2021 Nikhar Agrawal, Anton Bikineev, Matthew Borland,
Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert Holin, Bruno
Lalande, John Maddock, Evan Miller, Jeremy Murphy, Matthew Pulver, Johan Råde,
Gautam Sewani, Benjamin Sobotta, Nicholas Thompson, 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>)
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