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<html>
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<head>
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<link rel="up" href="../fp_facets.html" title="Facets for Floating-Point Infinities and NaNs">
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<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
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<td align="center"><a href="../../../../../../index.html">Home</a></td>
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<a accesskey="p" href="reference.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../fp_facets.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="portability.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
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<div class="section">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="math_toolkit.fp_facets.examples"></a><a class="link" href="examples.html" title="Examples">Examples</a>
|
||||
</h3></div></div></div>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.examples.h0"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.examples.simple_example_with_std_stringst"></a></span><a class="link" href="examples.html#math_toolkit.fp_facets.examples.simple_example_with_std_stringst">Simple
|
||||
example with std::stringstreams</a>
|
||||
</h6>
|
||||
<pre class="programlisting"><span class="identifier">locale</span> <span class="identifier">old_locale</span><span class="special">;</span>
|
||||
<span class="identifier">locale</span> <span class="identifier">tmp_locale</span><span class="special">(</span><span class="identifier">old_locale</span><span class="special">,</span> <span class="keyword">new</span> <span class="identifier">nonfinite_num_put</span><span class="special"><</span><span class="keyword">char</span><span class="special">>);</span>
|
||||
<span class="identifier">locale</span> <span class="identifier">new_locale</span><span class="special">(</span><span class="identifier">tmp_locale</span><span class="special">,</span> <span class="keyword">new</span> <span class="identifier">nonfinite_num_get</span><span class="special"><</span><span class="keyword">char</span><span class="special">>);</span>
|
||||
</pre>
|
||||
<pre class="programlisting"><span class="identifier">stringstream</span> <span class="identifier">ss</span><span class="special">;</span>
|
||||
<span class="identifier">ss</span><span class="special">.</span><span class="identifier">imbue</span><span class="special">(</span><span class="identifier">new_locale</span><span class="special">);</span>
|
||||
<span class="keyword">double</span> <span class="identifier">inf</span> <span class="special">=</span> <span class="identifier">numeric_limits</span><span class="special"><</span><span class="keyword">double</span><span class="special">>::</span><span class="identifier">infinity</span><span class="special">();</span>
|
||||
<span class="identifier">ss</span> <span class="special"><<</span> <span class="identifier">inf</span><span class="special">;</span> <span class="comment">// Write out.</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">ss</span><span class="special">.</span><span class="identifier">str</span><span class="special">()</span> <span class="special">==</span> <span class="string">"inf"</span><span class="special">);</span>
|
||||
<span class="keyword">double</span> <span class="identifier">r</span><span class="special">;</span>
|
||||
<span class="identifier">ss</span> <span class="special">>></span> <span class="identifier">r</span><span class="special">;</span> <span class="comment">// Read back in.</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">inf</span> <span class="special">==</span> <span class="identifier">r</span><span class="special">);</span> <span class="comment">// Confirms that the double values really are identical.</span>
|
||||
|
||||
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"infinity output was "</span> <span class="special"><<</span> <span class="identifier">ss</span><span class="special">.</span><span class="identifier">str</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span>
|
||||
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"infinity input was "</span> <span class="special"><<</span> <span class="identifier">r</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span>
|
||||
<span class="comment">// But the string representation of r displayed will be the native type</span>
|
||||
<span class="comment">// because, when it was constructed, cout had NOT been imbued</span>
|
||||
<span class="comment">// with the new locale containing the nonfinite_numput facet.</span>
|
||||
<span class="comment">// So the cout output will be "1.#INF on MS platforms</span>
|
||||
<span class="comment">// and may be "inf" or other string representation on other platforms.</span>
|
||||
</pre>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.examples.h1"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.examples.use_with_lexical_cast"></a></span><a class="link" href="examples.html#math_toolkit.fp_facets.examples.use_with_lexical_cast">Use with
|
||||
lexical_cast</a>
|
||||
</h6>
|
||||
<div class="note"><table border="0" summary="Note">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
|
||||
<th align="left">Note</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top"><p>
|
||||
From Boost 1.48, lexical_cast no longer uses stringstreams internally,
|
||||
and is now able to handle infinities and NaNs natively on most platforms.
|
||||
</p></td></tr>
|
||||
</table></div>
|
||||
<p>
|
||||
Without using a new locale that contains the nonfinite facets, previous versions
|
||||
of <code class="computeroutput"><span class="identifier">lexical_cast</span></code> using stringstream
|
||||
were not portable (and often failed) if nonfinite values are found.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">locale</span> <span class="identifier">old_locale</span><span class="special">;</span>
|
||||
<span class="identifier">locale</span> <span class="identifier">tmp_locale</span><span class="special">(</span><span class="identifier">old_locale</span><span class="special">,</span> <span class="keyword">new</span> <span class="identifier">nonfinite_num_put</span><span class="special"><</span><span class="keyword">char</span><span class="special">>);</span>
|
||||
<span class="identifier">locale</span> <span class="identifier">new_locale</span><span class="special">(</span><span class="identifier">tmp_locale</span><span class="special">,</span> <span class="keyword">new</span> <span class="identifier">nonfinite_num_get</span><span class="special"><</span><span class="keyword">char</span><span class="special">>);</span>
|
||||
</pre>
|
||||
<p>
|
||||
Although other examples imbue individual streams with the new locale, for
|
||||
the streams constructed inside lexical_cast, it was necesary to assign to
|
||||
a global locale.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">locale</span><span class="special">::</span><span class="identifier">global</span><span class="special">(</span><span class="identifier">new_locale</span><span class="special">);</span>
|
||||
</pre>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">lexical_cast</span></code> then works as
|
||||
expected, even with infinity and NaNs.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">double</span> <span class="identifier">x</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">lexical_cast</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="string">"inf"</span><span class="special">);</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric</span><span class="special">:</span><span class="identifier">limits</span><span class="special"><</span><span class="keyword">double</span><span class="special">>::</span><span class="identifier">infinity</span><span class="special">());</span>
|
||||
|
||||
<span class="identifier">string</span> <span class="identifier">s</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">lexical_cast</span><span class="special"><</span><span class="identifier">string</span><span class="special">>(</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="keyword">double</span><span class="special">>::</span><span class="identifier">infinity</span><span class="special">());</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">s</span> <span class="special">==</span> <span class="string">"inf"</span><span class="special">);</span>
|
||||
</pre>
|
||||
<div class="warning"><table border="0" summary="Warning">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../../../doc/src/images/warning.png"></td>
|
||||
<th align="left">Warning</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top"><p>
|
||||
If you use stringstream inside your functions, you may still need to use
|
||||
a global locale to handle nonfinites correctly. Or you need to imbue your
|
||||
stringstream with suitable get and put facets.
|
||||
</p></td></tr>
|
||||
</table></div>
|
||||
<div class="warning"><table border="0" summary="Warning">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../../../doc/src/images/warning.png"></td>
|
||||
<th align="left">Warning</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top"><p>
|
||||
You should be aware that the C++ specification does not explicitly require
|
||||
that input from decimal digits strings converts with rounding to the nearest
|
||||
representable floating-point binary value. (In contrast, decimal digits
|
||||
read by the compiler, for example by an assignment like <code class="computeroutput"><span class="keyword">double</span>
|
||||
<span class="identifier">d</span> <span class="special">=</span>
|
||||
<span class="number">1.234567890123456789</span></code>, are guaranteed
|
||||
to assign the nearest representable value to double d). This implies that,
|
||||
no matter how many decimal digits you provide, there is a potential uncertainty
|
||||
of 1 least significant bit in the resulting binary value.
|
||||
</p></td></tr>
|
||||
</table></div>
|
||||
<p>
|
||||
See <a href="http://en.wikipedia.org/wiki/Floating_point#Representable_numbers.2C_conversion_and_rounding" target="_top">conversion
|
||||
and rounding</a> for more information on <span class="emphasis"><em>nearest representable</em></span>
|
||||
and <span class="emphasis"><em>rounding</em></span> and <a href="http://www.exploringbinary.com/" target="_top">Exploring
|
||||
Binary</a> for much detail on input and round-tripping difficulties.
|
||||
</p>
|
||||
<p>
|
||||
Most iostream libraries do in fact achieve the desirable <span class="emphasis"><em>nearest
|
||||
representable floating-point binary value</em></span> for all values of input.
|
||||
However one popular STL library does not quite achieve this for 64-bit doubles.
|
||||
See <a href="http://connect.microsoft.com/VisualStudio/feedback/details/98770/decimal-digit-string-input-to-double-may-be-1-bit-wrong" target="_top">Decimal
|
||||
digit string input to double may be 1 bit wrong</a> for the bizarre full
|
||||
details.
|
||||
</p>
|
||||
<p>
|
||||
If you are expecting to 'round-trip' <code class="computeroutput"><span class="identifier">lexical_cast</span></code>
|
||||
or <code class="computeroutput"><span class="identifier">serialization</span></code>, for example
|
||||
archiving and loading, and want to be <span class="bold"><strong>absolutely certain
|
||||
that you will always get an exactly identical double value binary pattern</strong></span>,
|
||||
you should use the suggested 'workaround' below that is believed to work
|
||||
on all platforms.
|
||||
</p>
|
||||
<p>
|
||||
You should output using all potentially significant decimal digits, by setting
|
||||
stream precision to <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="keyword">double</span><span class="special">>::</span><span class="identifier">max_digits10</span></code>, (or for the appropriate floating-point
|
||||
type, if not double) and crucially, <span class="bold"><strong>require <code class="computeroutput"><span class="identifier">scientific</span></code> format</strong></span>, not <code class="computeroutput"><span class="identifier">fixed</span></code> or automatic (default), for example:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">double</span> <span class="identifier">output_value</span> <span class="special">=</span> <span class="identifier">any</span> <span class="identifier">value</span><span class="special">;</span>
|
||||
<span class="identifier">std</span><span class="special">::</span><span class="identifier">stringstream</span> <span class="identifier">s</span><span class="special">;</span>
|
||||
<span class="identifier">s</span> <span class="special"><<</span> <span class="identifier">setprecison</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="keyword">double</span><span class="special">>::</span><span class="identifier">max_digits10</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">scientific</span> <span class="special"><<</span> <span class="identifier">output_value</span><span class="special">;</span>
|
||||
<span class="identifier">s</span> <span class="special">>></span> <span class="identifier">input_value</span><span class="special">;</span>
|
||||
</pre>
|
||||
<h5>
|
||||
<a name="math_toolkit.fp_facets.examples.h2"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.examples.use_with_serialization_archives"></a></span><a class="link" href="examples.html#math_toolkit.fp_facets.examples.use_with_serialization_archives">Use
|
||||
with serialization archives</a>
|
||||
</h5>
|
||||
<p>
|
||||
It is vital that the same locale is used when an archive is saved and when
|
||||
it is loaded. Otherwise, loading the archive may fail. By default, archives
|
||||
are saved and loaded with a classic C locale with a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">archive</span><span class="special">::</span><span class="identifier">codecvt_null</span></code>
|
||||
facet added. Normally you do not have to worry about that.
|
||||
</p>
|
||||
<p>
|
||||
The constructors for the archive classes, as a side-effect, imbue the stream
|
||||
with such a locale. However, if you want to use the facets <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code> and <code class="computeroutput"><span class="identifier">nonfinite_num_get</span></code>
|
||||
with archives, then you have to manage the locale manually. That is done
|
||||
by calling the archive constructor with the flag <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">archive</span><span class="special">::</span><span class="identifier">no_codecvt</span></code>,
|
||||
thereby ensuring that the archive constructor will <span class="bold"><strong>not
|
||||
imbue the stream with a new locale</strong></span>.
|
||||
</p>
|
||||
<p>
|
||||
The following code shows how to use <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>
|
||||
with a <code class="computeroutput"><span class="identifier">text_oarchive</span></code>.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">locale</span> <span class="identifier">default_locale</span><span class="special">(</span><span class="identifier">locale</span><span class="special">::</span><span class="identifier">classic</span><span class="special">(),</span> <span class="keyword">new</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">archive</span><span class="special">::</span><span class="identifier">codecvt_null</span><span class="special"><</span><span class="keyword">char</span><span class="special">>);</span>
|
||||
<span class="identifier">locale</span> <span class="identifier">my_locale</span><span class="special">(</span><span class="identifier">default_locale</span><span class="special">,</span> <span class="keyword">new</span> <span class="identifier">nonfinite_num_put</span><span class="special"><</span><span class="keyword">char</span><span class="special">>);</span>
|
||||
|
||||
<span class="identifier">ofstream</span> <span class="identifier">ofs</span><span class="special">(</span><span class="string">"test.txt"</span><span class="special">);</span>
|
||||
<span class="identifier">ofs</span><span class="special">.</span><span class="identifier">imbue</span><span class="special">(</span><span class="identifier">my_locale</span><span class="special">);</span>
|
||||
|
||||
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">archive</span><span class="special">::</span><span class="identifier">text_oarchive</span> <span class="identifier">oa</span><span class="special">(</span><span class="identifier">ofs</span><span class="special">,</span> <span class="identifier">no_codecvt</span><span class="special">);</span>
|
||||
|
||||
<span class="keyword">double</span> <span class="identifier">x</span> <span class="special">=</span> <span class="identifier">numeric_limits</span><span class="special"><</span><span class="keyword">double</span><span class="special">>::</span><span class="identifier">infinity</span><span class="special">();</span>
|
||||
<span class="identifier">oa</span> <span class="special">&</span> <span class="identifier">x</span><span class="special">;</span>
|
||||
</pre>
|
||||
<p>
|
||||
The same method works with <code class="computeroutput"><span class="identifier">nonfinite_num_get</span></code>
|
||||
and <code class="computeroutput"><span class="identifier">text_iarchive</span></code>.
|
||||
</p>
|
||||
<p>
|
||||
If you use the <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>
|
||||
with <code class="computeroutput"><span class="identifier">trap_infinity</span></code> and/or
|
||||
<code class="computeroutput"><span class="identifier">trap_nan</span></code> flag with a serialization
|
||||
archive, then you must set the exception mask of the stream. Serialization
|
||||
archives do not check the stream state.
|
||||
</p>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.examples.h3"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.examples.other_examples"></a></span><a class="link" href="examples.html#math_toolkit.fp_facets.examples.other_examples">Other
|
||||
examples</a>
|
||||
</h6>
|
||||
<p>
|
||||
<a href="../../../../example/nonfinite_facet_simple.cpp" target="_top">nonfinite_facet_simple.cpp</a>
|
||||
give some more simple demonstrations of the difference between using classic
|
||||
C locale and constructing a C99 infinty and NaN compliant locale for input
|
||||
and output.
|
||||
</p>
|
||||
<p>
|
||||
See <a href="../../../../example/nonfinite_facet_sstream.cpp" target="_top">nonfinite_facet_sstream.cpp</a>
|
||||
for this example of use with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">stringstream</span></code>s.
|
||||
</p>
|
||||
<p>
|
||||
For an example of how to enforce the MSVC 'legacy' "1.#INF" and
|
||||
"1.#QNAN" representations of infinity and NaNs, for input and output,
|
||||
see <a href="../../../../example/nonfinite_legacy.cpp" target="_top">nonfinite_legacy.cpp</a>.
|
||||
</p>
|
||||
<p>
|
||||
Treatment of signaling NaN is demonstrated at <a href="../../../../example/nonfinite_signaling_NaN.cpp" target="_top">../../example/nonfinite_signaling_NaN.cpp</a>
|
||||
</p>
|
||||
<p>
|
||||
Example <a href="../../../../example/nonfinite_loopback_ok.cpp" target="_top">../../example/nonfinite_loopback_ok.cpp</a>
|
||||
shows loopback works OK.
|
||||
</p>
|
||||
<p>
|
||||
Example <a href="../../../../example/nonfinite_num_facet.cpp" target="_top">../../example/nonfinite_num_facet.cpp</a>
|
||||
shows output and re-input of various finite and nonfinite values.
|
||||
</p>
|
||||
<p>
|
||||
A simple example of trapping nonfinite output is at <a href="../../../../example/nonfinite_num_facet_trap.cpp" target="_top">nonfinite_num_facet_trap.cpp</a>.
|
||||
</p>
|
||||
<p>
|
||||
A very basic example of using Boost.Archive is at <a href="../../../../example/nonfinite_serialization_archives.cpp" target="_top">../../example/nonfinite_serialization_archives.cpp</a>.
|
||||
</p>
|
||||
<p>
|
||||
A full demonstration of serialization by Francois Mauger is at <a href="../../../../example/nonfinite_num_facet_serialization.cpp" target="_top">../../example/nonfinite_num_facet_serialization.cpp</a>
|
||||
</p>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2006-2010, 2012-2014 Nikhar Agrawal,
|
||||
Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
|
||||
Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan Råde, Gautam Sewani,
|
||||
Benjamin Sobotta, 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>)
|
||||
</p>
|
||||
</div></td>
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<div class="spirit-nav">
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<a accesskey="p" href="../fp_facets.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../fp_facets.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="reference.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
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<div class="section">
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<div class="titlepage"><div><div><h3 class="title">
|
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<a name="math_toolkit.fp_facets.facets_intro"></a><a class="link" href="facets_intro.html" title="Introduction">Introduction</a>
|
||||
</h3></div></div></div>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.facets_intro.h0"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.facets_intro.the_problem"></a></span><a class="link" href="facets_intro.html#math_toolkit.fp_facets.facets_intro.the_problem">The
|
||||
Problem</a>
|
||||
</h6>
|
||||
<p>
|
||||
The C++98 standard does not specify how <span class="emphasis"><em>infinity</em></span> and
|
||||
<span class="emphasis"><em>NaN</em></span> are represented in text streams. As a result, different
|
||||
platforms use different string representations. This can cause undefined
|
||||
behavior when text files are moved between different platforms. Some platforms
|
||||
cannot even input parse their own output! So 'route-tripping' or loopback
|
||||
of output to input is not possible. For instance, the following test fails
|
||||
with MSVC:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">stringstream</span> <span class="identifier">ss</span><span class="special">;</span>
|
||||
<span class="keyword">double</span> <span class="identifier">inf</span> <span class="special">=</span> <span class="identifier">numeric_limits</span><span class="special"><</span><span class="keyword">double</span><span class="special">>::</span><span class="identifier">infinity</span><span class="special">();</span>
|
||||
<span class="keyword">double</span> <span class="identifier">r</span><span class="special">;</span>
|
||||
<span class="identifier">ss</span> <span class="special"><<</span> <span class="identifier">inf</span><span class="special">;</span> <span class="comment">// Write out.</span>
|
||||
<span class="identifier">ss</span> <span class="special">>></span> <span class="identifier">r</span><span class="special">;</span> <span class="comment">// Read back in.</span>
|
||||
|
||||
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"infinity output was "</span> <span class="special"><<</span> <span class="identifier">inf</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// 1.#INF</span>
|
||||
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"infinity input was "</span> <span class="special"><<</span> <span class="identifier">r</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> <span class="comment">// 1</span>
|
||||
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">inf</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">);</span> <span class="comment">// Fails!</span>
|
||||
</pre>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.facets_intro.h1"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.facets_intro.the_solution"></a></span><a class="link" href="facets_intro.html#math_toolkit.fp_facets.facets_intro.the_solution">The
|
||||
Solution</a>
|
||||
</h6>
|
||||
<p>
|
||||
The facets <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>
|
||||
and <code class="computeroutput"><span class="identifier">nonfinite_num_get</span></code> format
|
||||
and parse all floating-point numbers, including <code class="computeroutput"><span class="identifier">infinity</span></code>
|
||||
and <code class="computeroutput"><span class="identifier">NaN</span></code>, in a consistent
|
||||
and portable manner.
|
||||
</p>
|
||||
<p>
|
||||
The following test succeeds with MSVC.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">locale</span> <span class="identifier">old_locale</span><span class="special">;</span>
|
||||
<span class="identifier">locale</span> <span class="identifier">tmp_locale</span><span class="special">(</span><span class="identifier">old_locale</span><span class="special">,</span> <span class="keyword">new</span> <span class="identifier">nonfinite_num_put</span><span class="special"><</span><span class="keyword">char</span><span class="special">>);</span>
|
||||
<span class="identifier">locale</span> <span class="identifier">new_locale</span><span class="special">(</span><span class="identifier">tmp_locale</span><span class="special">,</span> <span class="keyword">new</span> <span class="identifier">nonfinite_num_get</span><span class="special"><</span><span class="keyword">char</span><span class="special">>);</span>
|
||||
</pre>
|
||||
<div class="tip"><table border="0" summary="Tip">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../../../../doc/src/images/tip.png"></td>
|
||||
<th align="left">Tip</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top">
|
||||
<p>
|
||||
To add two facets, <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>
|
||||
and <code class="computeroutput"><span class="identifier">nonfinite_num_get</span></code>,
|
||||
you may have to add one at a time, using a temporary locale.
|
||||
</p>
|
||||
<p>
|
||||
Or you can create a new locale in one step
|
||||
</p>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">locale</span> <span class="identifier">new_locale</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">locale</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">locale</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">locale</span><span class="special">(),</span> <span class="keyword">new</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">nonfinite_num_put</span><span class="special"><</span><span class="keyword">char</span><span class="special">>),</span> <span class="keyword">new</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">nonfinite_num_get</span><span class="special"><</span><span class="keyword">char</span><span class="special">>));</span></code>
|
||||
</p>
|
||||
<p>
|
||||
and, for example, use it to imbue an input and output stringstream.
|
||||
</p>
|
||||
</td></tr>
|
||||
</table></div>
|
||||
<div class="tip"><table border="0" summary="Tip">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../../../../doc/src/images/tip.png"></td>
|
||||
<th align="left">Tip</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top"><p>
|
||||
To just change an input or output stream, you can concisely write <code class="computeroutput"><span class="identifier">cout</span><span class="special">.</span><span class="identifier">imbue</span> <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">locale</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">locale</span><span class="special">(),</span> <span class="keyword">new</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">nonfinite_num_put</span><span class="special"><</span><span class="keyword">char</span><span class="special">>));</span></code> or <code class="computeroutput"><span class="identifier">cin</span><span class="special">.</span><span class="identifier">imbue</span> <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">locale</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">locale</span><span class="special">(),</span> <span class="keyword">new</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">nonfinite_num_get</span><span class="special"><</span><span class="keyword">char</span><span class="special">>));</span></code>
|
||||
</p></td></tr>
|
||||
</table></div>
|
||||
<pre class="programlisting"><span class="identifier">stringstream</span> <span class="identifier">ss</span><span class="special">;</span>
|
||||
<span class="identifier">ss</span><span class="special">.</span><span class="identifier">imbue</span><span class="special">(</span><span class="identifier">new_locale</span><span class="special">);</span>
|
||||
<span class="keyword">double</span> <span class="identifier">inf</span> <span class="special">=</span> <span class="identifier">numeric_limits</span><span class="special"><</span><span class="keyword">double</span><span class="special">>::</span><span class="identifier">infinity</span><span class="special">();</span>
|
||||
<span class="identifier">ss</span> <span class="special"><<</span> <span class="identifier">inf</span><span class="special">;</span> <span class="comment">// Write out.</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">ss</span><span class="special">.</span><span class="identifier">str</span><span class="special">()</span> <span class="special">==</span> <span class="string">"inf"</span><span class="special">);</span>
|
||||
<span class="keyword">double</span> <span class="identifier">r</span><span class="special">;</span>
|
||||
<span class="identifier">ss</span> <span class="special">>></span> <span class="identifier">r</span><span class="special">;</span> <span class="comment">// Read back in.</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">inf</span> <span class="special">==</span> <span class="identifier">r</span><span class="special">);</span> <span class="comment">// Confirms that the double values really are identical.</span>
|
||||
|
||||
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"infinity output was "</span> <span class="special"><<</span> <span class="identifier">ss</span><span class="special">.</span><span class="identifier">str</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span>
|
||||
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"infinity input was "</span> <span class="special"><<</span> <span class="identifier">r</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span>
|
||||
<span class="comment">// But the string representation of r displayed will be the native type</span>
|
||||
<span class="comment">// because, when it was constructed, cout had NOT been imbued</span>
|
||||
<span class="comment">// with the new locale containing the nonfinite_numput facet.</span>
|
||||
<span class="comment">// So the cout output will be "1.#INF on MS platforms</span>
|
||||
<span class="comment">// and may be "inf" or other string representation on other platforms.</span>
|
||||
</pre>
|
||||
<h5>
|
||||
<a name="math_toolkit.fp_facets.facets_intro.h2"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.facets_intro.c_0x_standard_for_output_of_infi"></a></span><a class="link" href="facets_intro.html#math_toolkit.fp_facets.facets_intro.c_0x_standard_for_output_of_infi">C++0X
|
||||
standard for output of infinity and NaN</a>
|
||||
</h5>
|
||||
<p>
|
||||
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf" target="_top">C++0X
|
||||
(final) draft standard</a> does not explicitly specify the representation
|
||||
(and input) of nonfinite values, leaving it implementation-defined. So without
|
||||
some specific action, input and output of nonfinite values is not portable.
|
||||
</p>
|
||||
<h5>
|
||||
<a name="math_toolkit.fp_facets.facets_intro.h3"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.facets_intro.c99_standard_for_output_of_infin"></a></span><a class="link" href="facets_intro.html#math_toolkit.fp_facets.facets_intro.c99_standard_for_output_of_infin">C99
|
||||
standard for output of infinity and NaN</a>
|
||||
</h5>
|
||||
<p>
|
||||
The <a href="http://www.open-std.org/JTC1/SC22/WG14/www/docs/n1256.pdf" target="_top">C99
|
||||
standard</a> <span class="bold"><strong>does</strong></span> specify how infinity
|
||||
and NaN are formatted by printf and similar output functions, and parsed
|
||||
by scanf and similar input functions.
|
||||
</p>
|
||||
<p>
|
||||
The following string representations are used:
|
||||
</p>
|
||||
<div class="table">
|
||||
<a name="math_toolkit.fp_facets.facets_intro.c99_representation_of_infinity_a"></a><p class="title"><b>Table 2.1. C99 Representation of Infinity and NaN</b></p>
|
||||
<div class="table-contents"><table class="table" summary="C99 Representation of Infinity and NaN">
|
||||
<colgroup>
|
||||
<col>
|
||||
<col>
|
||||
</colgroup>
|
||||
<thead><tr>
|
||||
<th>
|
||||
<p>
|
||||
number
|
||||
</p>
|
||||
</th>
|
||||
<th>
|
||||
<p>
|
||||
string
|
||||
</p>
|
||||
</th>
|
||||
</tr></thead>
|
||||
<tbody>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Positive infinity
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
"inf" or "infinity"
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Positive NaN
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
"nan" or "nan(...)"
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Negative infinity
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
"-inf" or "-infinity"
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Negative NaN
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
"-nan" or "-nan(...)"
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table></div>
|
||||
</div>
|
||||
<br class="table-break"><p>
|
||||
So following C99 provides a sensible 'standard' way of handling input and
|
||||
output of nonfinites in C++, and this implementation follows most of these
|
||||
formats.
|
||||
</p>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.facets_intro.h4"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.facets_intro.signaling_nans"></a></span><a class="link" href="facets_intro.html#math_toolkit.fp_facets.facets_intro.signaling_nans">Signaling
|
||||
NaNs</a>
|
||||
</h6>
|
||||
<p>
|
||||
A particular type of NaN is the signaling NaN. The usual mechanism of signaling
|
||||
is by raising a floating-point exception. Signaling NaNs are defined by
|
||||
<a href="http://en.wikipedia.org/wiki/IEEE_floating-point_standard" target="_top">IEEE
|
||||
754-2008</a>.
|
||||
</p>
|
||||
<p>
|
||||
Floating-point values with layout <span class="emphasis"><em>s</em></span>111 1111 1<span class="emphasis"><em>a</em></span>xx
|
||||
xxxx xxxx xxxx xxxx xxxx where <span class="emphasis"><em>s</em></span> is the sign, <span class="emphasis"><em>x</em></span>
|
||||
is the payload, and bit <span class="emphasis"><em>a</em></span> determines the type of NaN.
|
||||
</p>
|
||||
<p>
|
||||
If bit <span class="emphasis"><em>a</em></span> = 1, it is a quiet NaN.
|
||||
</p>
|
||||
<p>
|
||||
If bit <span class="emphasis"><em>a</em></span> is zero and the payload <span class="emphasis"><em>x</em></span>
|
||||
is nonzero, then it is a signaling NaN.
|
||||
</p>
|
||||
<p>
|
||||
Although there has been theoretical interest in the ability of a signaling
|
||||
NaN to raise an exception, for example to prevent use of an uninitialised
|
||||
variable, in practice there appears to be no useful application of signaling
|
||||
NaNs for most current processors. <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf" target="_top">C++0X
|
||||
18.3.2.2</a> still specifies a (implementation-defined) representation
|
||||
for signaling NaN, and <code class="computeroutput"><span class="keyword">static</span> <span class="keyword">constexpr</span> <span class="keyword">bool</span> <span class="identifier">has_signaling_NaN</span></code> a method of checking
|
||||
if a floating-point type has a representation for signaling NaN.
|
||||
</p>
|
||||
<p>
|
||||
But in practice, most platforms treat signaling NaNs in the same as quiet
|
||||
NaNs. So, for example, they are represented by "nan" on output
|
||||
in <a href="http://www.open-std.org/JTC1/SC22/WG14/www/docs/n1256.pdf" target="_top">C99</a>
|
||||
format, and output as <code class="computeroutput"><span class="number">1.</span><span class="special">#</span><span class="identifier">QNAN</span></code> by Microsoft compilers.
|
||||
</p>
|
||||
<div class="note"><table border="0" summary="Note">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
|
||||
<th align="left">Note</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top">
|
||||
<p>
|
||||
The C99 standard does not distinguish between the quiet NaN and signaling
|
||||
NaN values. A quiet NaN propagates through almost every arithmetic operation
|
||||
without raising a floating-point exception; a signaling NaN generally raises
|
||||
a floating-point exception when occurring as an arithmetic operand.
|
||||
</p>
|
||||
<p>
|
||||
C99 specification does not define the behavior of signaling NaNs. NaNs
|
||||
created by IEC 60559 operations are always quiet. Therefore this implementation
|
||||
follows C99, and treats the signaling NaN bit as just a part of the NaN
|
||||
payload field. So this implementation does not distinguish between the
|
||||
two classes of NaN.
|
||||
</p>
|
||||
</td></tr>
|
||||
</table></div>
|
||||
<div class="note"><table border="0" summary="Note">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
|
||||
<th align="left">Note</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top">
|
||||
<p>
|
||||
An implementation may give zero and non-numeric values (such as infinities
|
||||
and NaNs) a sign or may leave them unsigned. Wherever such values are unsigned,
|
||||
any requirement in the C99 Standard to retrieve the sign shall produce
|
||||
an unspecified sign, and any requirement to set the sign shall be ignored.
|
||||
</p>
|
||||
<p>
|
||||
This might apply to user-defined types, but in practice built-in floating-point
|
||||
types <code class="computeroutput"><span class="keyword">float</span></code>, <code class="computeroutput"><span class="keyword">double</span></code> and <code class="computeroutput"><span class="keyword">long</span>
|
||||
<span class="keyword">double</span></code> have well-behaved signs.
|
||||
</p>
|
||||
</td></tr>
|
||||
</table></div>
|
||||
<p>
|
||||
The numbers can be of type <code class="computeroutput"><span class="keyword">float</span></code>,
|
||||
<code class="computeroutput"><span class="keyword">double</span></code> and <code class="computeroutput"><span class="keyword">long</span>
|
||||
<span class="keyword">double</span></code>. An optional + sign can be
|
||||
used with positive numbers (controlled by ios manipulator <code class="computeroutput"><span class="identifier">showpos</span></code>).
|
||||
The function <code class="computeroutput"><span class="identifier">printf</span></code> and similar
|
||||
C++ functions use standard formatting flags to put all lower or all upper
|
||||
case (controlled by <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ios</span></code> manipulator <code class="computeroutput"><span class="identifier">uppercase</span></code>
|
||||
and <code class="computeroutput"><span class="identifier">lowercase</span></code>).
|
||||
</p>
|
||||
<p>
|
||||
The function <code class="computeroutput"><span class="identifier">scanf</span></code> and similar
|
||||
input functions are case-insensitive.
|
||||
</p>
|
||||
<p>
|
||||
The dots in <code class="computeroutput"><span class="identifier">nan</span><span class="special">(...)</span></code>
|
||||
stand for an arbitrary string. The meaning of that string is implementation
|
||||
dependent. It can be used to convey extra information about the NaN, from
|
||||
the 'payload'. A particular value of the payload might be used to indicate
|
||||
a <span class="emphasis"><em>missing value</em></span>, for example.
|
||||
</p>
|
||||
<p>
|
||||
This library uses the string representations specified by the C99 standard.
|
||||
</p>
|
||||
<p>
|
||||
An example of an implementation that optionally includes the NaN payload
|
||||
information is at <a href="http://publib.boulder.ibm.com/infocenter/zos/v1r10/index.jsp?topic=/com.ibm.zos.r10.bpxbd00/fprints.htm" target="_top">AIX
|
||||
NaN fprintf</a>. That implementation specifies for Binary Floating Point
|
||||
NANs:
|
||||
</p>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
A NaN ordinal sequence is a left-parenthesis character '(', followed
|
||||
by a digit sequence representing an integer n, where 1 <= n <=
|
||||
INT_MAX-1, followed by a right-parenthesis character ')'.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
The integer value, n, is determined by the fraction bits of the NaN argument
|
||||
value as follows:
|
||||
</li>
|
||||
<li class="listitem">
|
||||
For a signalling NaN value, NaN fraction bits are reversed (left to right)
|
||||
to produce bits (right to left) of an even integer value, 2*n. Then formatted
|
||||
output functions produce a (signalling) NaN ordinal sequence corresponding
|
||||
to the integer value n.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
For a quiet NaN value, NaN fraction bits are reversed (left to right)
|
||||
to produce bits (right to left) of an odd integer value, 2*n-1. Then
|
||||
formatted output functions produce a (quiet) NaN ordinal sequence corresponding
|
||||
to the integer value n.
|
||||
</li>
|
||||
</ul></div>
|
||||
<div class="warning"><table border="0" summary="Warning">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../../../doc/src/images/warning.png"></td>
|
||||
<th align="left">Warning</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top"><p>
|
||||
This implementation does not (yet) provide output of, or access to, the
|
||||
NaN payload.
|
||||
</p></td></tr>
|
||||
</table></div>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2006-2010, 2012-2014 Nikhar Agrawal,
|
||||
Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
|
||||
Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan Råde, Gautam Sewani,
|
||||
Benjamin Sobotta, 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>)
|
||||
</p>
|
||||
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|
||||
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|
||||
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|
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|
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|
||||
</h3></div></div></div>
|
||||
<p>
|
||||
This library uses the floating-point number classification and sign-bit from
|
||||
Boost.Math library, and should work on all platforms where that library works.
|
||||
See the portability information for that library.
|
||||
</p>
|
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|
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<td align="right"><div class="copyright-footer">Copyright © 2006-2010, 2012-2014 Nikhar Agrawal,
|
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Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
|
||||
Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan Råde, Gautam Sewani,
|
||||
Benjamin Sobotta, 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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|
||||
<a name="math_toolkit.fp_facets.rationale"></a><a class="link" href="rationale.html" title="Design Rationale">Design Rationale</a>
|
||||
</h3></div></div></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
The flags are implemented as a const data member of the facet. Facets
|
||||
are reference counted, and locales can share facets. Therefore changing
|
||||
the flags of a facet would have effects that are hard to predict. An
|
||||
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>.
|
||||
Then one could safely modify the flags, and one could define manipulators
|
||||
that do so. However, for that to work with dynamically linked libraries,
|
||||
a <code class="computeroutput"><span class="special">.</span><span class="identifier">cpp</span></code>
|
||||
file would have to be added to the library. It was judged be more desirable
|
||||
to have a header-only library, than to have mutable flags and manipulators.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
The facet <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>
|
||||
throws an exception when the <code class="computeroutput"><span class="identifier">trap_infinity</span></code>
|
||||
or <code class="computeroutput"><span class="identifier">trap_nan</span></code> flag is set
|
||||
and an attempt is made to format infinity or NaN. It would be better
|
||||
if the facet set the <code class="computeroutput"><span class="identifier">fail</span> <span class="identifier">bit</span></code> of the stream. However, facets
|
||||
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
|
||||
state.
|
||||
</li>
|
||||
</ul></div>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2006-2010, 2012-2014 Nikhar Agrawal,
|
||||
Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
|
||||
Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan Råde, Gautam Sewani,
|
||||
Benjamin Sobotta, 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>)
|
||||
</p>
|
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|
||||
<a name="math_toolkit.fp_facets.reference"></a><a class="link" href="reference.html" title="Reference">Reference</a>
|
||||
</h3></div></div></div>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.reference.h0"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.reference.the_facet_nonfinite_num_put"></a></span><a class="link" href="reference.html#math_toolkit.fp_facets.reference.the_facet_nonfinite_num_put">The
|
||||
Facet <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code></a>
|
||||
</h6>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span>
|
||||
<span class="keyword">class</span> <span class="identifier">CharType</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">OutputIterator</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">ostreambuf_iterator</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">></span>
|
||||
<span class="special">></span>
|
||||
<span class="keyword">class</span> <span class="identifier">nonfinite_num_put</span><span class="special">;</span>
|
||||
</pre>
|
||||
<p>
|
||||
The <code class="computeroutput"><span class="keyword">class</span> <span class="identifier">nonfinite_num_put</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">OutputIterator</span><span class="special">></span></code> is derived from <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">num_put</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">OutputIterator</span><span class="special">></span></code>. Thus it is a facet that formats numbers.
|
||||
The first template argument is the character type of the formatted strings,
|
||||
usually <code class="computeroutput"><span class="keyword">char</span></code> or <code class="computeroutput"><span class="keyword">wchar_t</span></code>. The second template argument is the
|
||||
type of iterator used to write the strings. It is required to be an output
|
||||
iterator. Usually the default <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostreambuf_iterator</span></code>
|
||||
is used. The public interface of the class consists of a single constructor
|
||||
only:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">nonfinite_num_put</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">flags</span> <span class="special">=</span> <span class="number">0</span><span class="special">);</span>
|
||||
</pre>
|
||||
<p>
|
||||
The flags argument (effectively optional because a default of <code class="computeroutput"> <span class="identifier">no_flags</span></code> is provided) is discussed below.
|
||||
The class template <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>
|
||||
is defined in the header <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">math</span><span class="special">/</span><span class="identifier">nonfinite_num_facets</span><span class="special">.</span><span class="identifier">hpp</span></code> and lives in the namespace <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span></code>.
|
||||
</p>
|
||||
<p>
|
||||
Unlike the C++ Standard facet <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">num_put</span></code>,
|
||||
the facet <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>
|
||||
formats <code class="computeroutput"><span class="identifier">infinity</span></code> and <code class="computeroutput"><span class="identifier">NaN</span></code> in a consistent and portable manner.
|
||||
It uses the following string representations:
|
||||
</p>
|
||||
<div class="informaltable"><table class="table">
|
||||
<colgroup>
|
||||
<col>
|
||||
<col>
|
||||
</colgroup>
|
||||
<thead><tr>
|
||||
<th>
|
||||
<p>
|
||||
Number
|
||||
</p>
|
||||
</th>
|
||||
<th>
|
||||
<p>
|
||||
String
|
||||
</p>
|
||||
</th>
|
||||
</tr></thead>
|
||||
<tbody>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Positive infinity
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
inf
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Positive NaN
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
nan
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Negative infinity
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
-inf
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Negative NaN
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
-nan
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table></div>
|
||||
<p>
|
||||
The numbers can be of type <code class="computeroutput"><span class="keyword">float</span></code>,
|
||||
<code class="computeroutput"><span class="keyword">double</span></code> and <code class="computeroutput"><span class="keyword">long</span>
|
||||
<span class="keyword">double</span></code>. The strings can be in all
|
||||
lower case or all upper case. An optional + sign can be used with positive
|
||||
numbers. This can be controlled with the <code class="computeroutput"><span class="identifier">uppercase</span></code>,
|
||||
<code class="computeroutput"><span class="identifier">lowercase</span></code>, <code class="computeroutput"><span class="identifier">showpos</span></code> and <code class="computeroutput"><span class="identifier">noshowpos</span></code>
|
||||
manipulators. Formatting of integers, boolean values and finite floating-point
|
||||
numbers is simply delegated to the normal <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">num_put</span></code>.
|
||||
</p>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.reference.h1"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.reference.facet_nonfinite_num_get"></a></span><a class="link" href="reference.html#math_toolkit.fp_facets.reference.facet_nonfinite_num_get">Facet
|
||||
<code class="computeroutput"><span class="identifier">nonfinite_num_get</span></code></a>
|
||||
</h6>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">CharType</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">InputIterator</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">istreambuf_iterator</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">></span> <span class="special">></span> <span class="keyword">class</span> <span class="identifier">nonfinite_num_get</span><span class="special">;</span>
|
||||
</pre>
|
||||
<p>
|
||||
The class <code class="computeroutput"><span class="identifier">nonfinite_num_get</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">InputIterator</span><span class="special">></span></code> is derived from <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">num_get</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">IntputIterator</span><span class="special">></span></code>. Thus it is a facet that parses strings
|
||||
that represent numbers. The first template argument is the character type
|
||||
of the strings, usually <code class="computeroutput"><span class="keyword">char</span></code>
|
||||
or <code class="computeroutput"><span class="keyword">wchar_t</span></code>. The second template
|
||||
argument is the type of iterator used to read the strings. It is required
|
||||
to be an input iterator. Usually the default is used. The public interface
|
||||
of the class consists of a single constructor only:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">nonfinite_num_get</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">flags</span> <span class="special">=</span> <span class="number">0</span><span class="special">);</span>
|
||||
</pre>
|
||||
<p>
|
||||
The flags argument is discussed below. The <code class="computeroutput"><span class="keyword">class</span>
|
||||
<span class="keyword">template</span> <span class="identifier">nonfinite_num_get</span></code>
|
||||
is defined in the header <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">math</span><span class="special">/</span><span class="identifier">nonfinite_num_facets</span><span class="special">.</span><span class="identifier">hpp</span></code> and lives in the <code class="computeroutput"><span class="keyword">namespace</span>
|
||||
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span></code>.
|
||||
</p>
|
||||
<p>
|
||||
Unlike the facet <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">num_get</span></code>, the facet <code class="computeroutput"><span class="identifier">nonfinite_num_get</span></code>
|
||||
parses strings that represent <code class="computeroutput"><span class="identifier">infinity</span></code>
|
||||
and <code class="computeroutput"><span class="identifier">NaN</span></code> in a consistent and
|
||||
portable manner. It recognizes precisely the string representations specified
|
||||
by the C99 standard:
|
||||
</p>
|
||||
<div class="informaltable"><table class="table">
|
||||
<colgroup>
|
||||
<col>
|
||||
<col>
|
||||
</colgroup>
|
||||
<thead><tr>
|
||||
<th>
|
||||
<p>
|
||||
Number
|
||||
</p>
|
||||
</th>
|
||||
<th>
|
||||
<p>
|
||||
String
|
||||
</p>
|
||||
</th>
|
||||
</tr></thead>
|
||||
<tbody>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Positive infinity
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
inf, infinity
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Positive NaN
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
nan, nan(...)
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Negative infinity
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
-inf, -infinity
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Negative NaN
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
-nan, -nan(...)
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table></div>
|
||||
<p>
|
||||
The numbers can be of type <code class="computeroutput"><span class="keyword">float</span></code>,
|
||||
<code class="computeroutput"><span class="keyword">double</span></code> and <code class="computeroutput"><span class="keyword">long</span>
|
||||
<span class="keyword">double</span></code>. The facet is case-insensitive.
|
||||
An optional + sign can be used with positive numbers. The dots in nan(...)
|
||||
stand for an arbitrary string usually containing the <span class="emphasis"><em>NaN payload</em></span>.
|
||||
Parsing of strings that represent integers, boolean values and finite floating-point
|
||||
numbers is delegated to <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">num_get</span></code>.
|
||||
</p>
|
||||
<p>
|
||||
When the facet parses a string that represents <code class="computeroutput"><span class="identifier">infinity</span></code>
|
||||
on a platform that lacks infinity, then the fail bit of the stream is set.
|
||||
</p>
|
||||
<p>
|
||||
When the facet parses a string that represents <code class="computeroutput"><span class="identifier">NaN</span></code>
|
||||
on a platform that lacks NaN, then the fail bit of the stream is set.
|
||||
</p>
|
||||
<h5>
|
||||
<a name="math_toolkit.fp_facets.reference.h2"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.reference.flags"></a></span><a class="link" href="reference.html#math_toolkit.fp_facets.reference.flags">Flags</a>
|
||||
</h5>
|
||||
<p>
|
||||
The constructors for <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>
|
||||
and <code class="computeroutput"><span class="identifier">nonfinite_num_get</span></code> take
|
||||
an optional bit flags argument. There are four different bit flags:
|
||||
</p>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
legacy
|
||||
</li>
|
||||
<li class="listitem">
|
||||
signed_zero
|
||||
</li>
|
||||
<li class="listitem">
|
||||
trap_infinity
|
||||
</li>
|
||||
<li class="listitem">
|
||||
trap_nan
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
The flags can be combined with the OR <code class="computeroutput"><span class="keyword">operator</span><span class="special">|</span></code>.
|
||||
</p>
|
||||
<p>
|
||||
The flags are defined in the header <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">math</span><span class="special">/</span><span class="identifier">nonfinite_num_facets</span><span class="special">.</span><span class="identifier">hpp</span></code> and live in the <code class="computeroutput"><span class="keyword">namespace</span>
|
||||
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span></code>.
|
||||
</p>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.reference.h3"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.reference.legacy"></a></span><a class="link" href="reference.html#math_toolkit.fp_facets.reference.legacy">legacy</a>
|
||||
</h6>
|
||||
<p>
|
||||
The legacy flag has no effect with the output facet <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>.
|
||||
</p>
|
||||
<p>
|
||||
If the legacy flag is used with the <code class="computeroutput"><span class="identifier">nonfinite_num_get</span></code>
|
||||
input facet, then the facet will recognize all the following string representations
|
||||
of <code class="computeroutput"><span class="identifier">infinity</span></code> and <code class="computeroutput"><span class="identifier">NaN</span></code>:
|
||||
</p>
|
||||
<div class="informaltable"><table class="table">
|
||||
<colgroup>
|
||||
<col>
|
||||
<col>
|
||||
</colgroup>
|
||||
<thead><tr>
|
||||
<th>
|
||||
<p>
|
||||
Number
|
||||
</p>
|
||||
</th>
|
||||
<th>
|
||||
<p>
|
||||
String
|
||||
</p>
|
||||
</th>
|
||||
</tr></thead>
|
||||
<tbody>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Positive infinity
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
inf, infinity, one#inf
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Positive NaN
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
nan, nan(...), nanq, nans, qnan, snan, one#ind, one#qnan, one#snan
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Negative infinity
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
-inf, -infinity, -one#inf
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
Negative NaN
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
-nan, -nan(...), -nanq, -nans, -qnan, -snan, -one#ind, - one#qnan,
|
||||
-one#snan
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
The numbers can be of type <code class="computeroutput"><span class="keyword">float</span></code>,
|
||||
<code class="computeroutput"><span class="keyword">double</span></code> and <code class="computeroutput"><span class="keyword">long</span> <span class="keyword">double</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
The facet is case-insensitive.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
An optional <code class="computeroutput"><span class="special">+</span></code> sign can be
|
||||
used with the positive values.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
The dots in <code class="computeroutput"><span class="identifier">nan</span><span class="special">(...)</span></code>
|
||||
stand for an arbitrary string.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<code class="computeroutput"><span class="identifier">one</span></code> stands for any string
|
||||
that <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">num_get</span></code> parses as the number <code class="computeroutput"><span class="number">1</span></code>, typically "1.#INF", "1.QNAN"
|
||||
but also "000001.#INF"...
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
The list includes a number of non-standard string representations of infinity
|
||||
and NaN that are used by various existing implementations of the C++ standard
|
||||
library, and also string representations used by other programming languages.
|
||||
</p>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.reference.h4"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.reference.signed_zero"></a></span><a class="link" href="reference.html#math_toolkit.fp_facets.reference.signed_zero">signed_zero</a>
|
||||
</h6>
|
||||
<p>
|
||||
If the <code class="computeroutput"><span class="identifier">signed_zero</span></code> flag is
|
||||
used with <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>,
|
||||
then the facet will always distinguish between positive and negative zero.
|
||||
It will format positive zero as "0" or "+0" and negative
|
||||
zero as "-0". The string representation of positive zero can be
|
||||
controlled with the <code class="computeroutput"><span class="identifier">showpos</span></code>
|
||||
and <code class="computeroutput"><span class="identifier">noshowpos</span></code> manipulators.
|
||||
</p>
|
||||
<p>
|
||||
The <code class="computeroutput"><span class="identifier">signed_zero</span> <span class="identifier">flag</span></code>
|
||||
has no effect with the input facet <code class="computeroutput"><span class="identifier">nonfinite_num_get</span></code>.
|
||||
The input facet <code class="computeroutput"><span class="identifier">nonfinite_num_get</span></code>
|
||||
always parses "0" and "+0" as positive zero and "-0"
|
||||
as negative zero, as do most implementations of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">num_get</span></code>.
|
||||
</p>
|
||||
<div class="note"><table border="0" summary="Note">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
|
||||
<th align="left">Note</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top"><p>
|
||||
If the <code class="computeroutput"><span class="identifier">signed_zero</span></code> flag
|
||||
is not set (the default), then a negative zero value will be displayed
|
||||
on output in whatever way the platform normally handles it. For most platforms,
|
||||
this it will format positive zero as "0" or "+0" and
|
||||
negative zero as "-0". But setting the <code class="computeroutput"><span class="identifier">signed_zero</span></code>
|
||||
flag may be more portable.
|
||||
</p></td></tr>
|
||||
</table></div>
|
||||
<div class="tip"><table border="0" summary="Tip">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../../../../doc/src/images/tip.png"></td>
|
||||
<th align="left">Tip</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top"><p>
|
||||
A negative zero value can be portably produced using the changesign function
|
||||
<code class="computeroutput"><span class="special">(</span><span class="identifier">changesign</span><span class="special">)(</span><span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">ValType</span><span class="special">>(</span><span class="number">0</span><span class="special">))</span></code>
|
||||
where <code class="computeroutput"><span class="identifier">ValType</span></code> is <code class="computeroutput"><span class="keyword">float</span></code>, <code class="computeroutput"><span class="keyword">double</span></code>
|
||||
or <code class="computeroutput"><span class="keyword">long</span> <span class="keyword">double</span></code>,
|
||||
or a User-Defined floating-point type (UDT) provided that this UDT has
|
||||
a sign and that the changesign function is implemented.
|
||||
</p></td></tr>
|
||||
</table></div>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.reference.h5"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.reference.trap_infinity"></a></span><a class="link" href="reference.html#math_toolkit.fp_facets.reference.trap_infinity">trap_infinity</a>
|
||||
</h6>
|
||||
<p>
|
||||
If the <code class="computeroutput"><span class="identifier">trap_infinity</span></code> flag
|
||||
is used with <code class="computeroutput"><span class="identifier">nonfinite_num_put</span></code>,
|
||||
then the facet will throw an exception of type <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">failure</span></code>
|
||||
when an attempt is made to format positive or negative infinity. If the facet
|
||||
is called from a stream insertion operator, then the stream will catch that
|
||||
exception and set either its <code class="computeroutput"><span class="identifier">fail</span>
|
||||
<span class="identifier">bit</span></code> or its <code class="computeroutput"><span class="identifier">bad</span>
|
||||
<span class="identifier">bit</span></code>. Which bit is set is platform
|
||||
dependent.
|
||||
</p>
|
||||
<p>
|
||||
If the <code class="computeroutput"><span class="identifier">trap_infinity</span></code> flag
|
||||
is used with <code class="computeroutput"><span class="identifier">nonfinite_num_get</span></code>,
|
||||
then the facet will set the <code class="computeroutput"><span class="identifier">fail</span>
|
||||
<span class="identifier">bit</span></code> of the stream when an attempt
|
||||
is made to parse a string that represents positive or negative infinity.
|
||||
</p>
|
||||
<p>
|
||||
(See Design Rationale below for a discussion of this inconsistency.)
|
||||
</p>
|
||||
<h6>
|
||||
<a name="math_toolkit.fp_facets.reference.h6"></a>
|
||||
<span class="phrase"><a name="math_toolkit.fp_facets.reference.trap_nan"></a></span><a class="link" href="reference.html#math_toolkit.fp_facets.reference.trap_nan">trap_nan</a>
|
||||
</h6>
|
||||
<p>
|
||||
Same as <code class="computeroutput"><span class="identifier">trap_infinity</span></code>, but
|
||||
positive and negative NaN are trapped instead.
|
||||
</p>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2006-2010, 2012-2014 Nikhar Agrawal,
|
||||
Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
|
||||
Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan Råde, Gautam Sewani,
|
||||
Benjamin Sobotta, 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>)
|
||||
</p>
|
||||
</div></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="facets_intro.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../fp_facets.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="examples.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
Reference in New Issue
Block a user