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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="math_toolkit.fp_facets.rationale"></a><a class="link" href="rationale.html" title="Design Rationale">Design Rationale</a>
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  29 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  30 <li class="listitem">
  31             The flags are implemented as a const data member of the facet. Facets
  32             are reference counted, and locales can share facets. Therefore changing
  33             the flags of a facet would have effects that are hard to predict. An
  34             alternative design would be to implement the flags using <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ios_base</span><span class="special">::</span><span class="identifier">xalloc</span></code> and <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ios_base</span><span class="special">::</span><span class="identifier">iword</span></code>.
  35             Then one could safely modify the flags, and one could define manipulators
  36             that do so. However, for that to work with dynamically linked libraries,
  37             a <code class="computeroutput"><span class="special">.</span><span class="identifier">cpp</span></code>
  38             file would have to be added to the library. It was judged be more desirable
  39             to have a header-only library, than to have mutable flags and manipulators.
  40           </li>
  41 <li class="listitem">
  42             The facet <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>
  43             throws an exception when the <code class="computeroutput"><span class="identifier">trap_infinity</span></code>
  44             or <code class="computeroutput"><span class="identifier">trap_nan</span></code> flag is set
  45             and an attempt is made to format infinity or NaN. It would be better
  46             if the facet set the <code class="computeroutput"><span class="identifier">fail</span> <span class="identifier">bit</span></code> of the stream. However, facets
  47             derived from <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">num_put</span></code> do not have access to the stream
  48             state.
  49           </li>
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  54 <td align="right"><div class="copyright-footer">Copyright &#169; 2006-2010, 2012-2014 Nikhar Agrawal,
  55       Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
  56       Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan R&#229;de, Gautam Sewani,
  57       Benjamin Sobotta, Thijs van den Berg, Daryle Walker and Xiaogang Zhang<p>
  58         Distributed under the Boost Software License, Version 1.0. (See accompanying
  59         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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