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137 lines
3.9 KiB
C++
137 lines
3.9 KiB
C++
/** nonfinite_serialization_archives.cpp
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*
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* Copyright (c) 2011 Paul A. Bristow
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*
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt
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* or copy at http://www.boost.org/LICENSE_1_0.txt)
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*
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* This very simple program illustrates how to use the
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* `boost/math/nonfinite_num_facets.hpp' to obtain C99
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* representation of infinity and NaN.
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* From the original Floating Point Utilities contribution by Johan Rade.
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* Floating Point Utility library has been accepted into Boost,
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* but the utilities are incorporated into Boost.Math library.
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*
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\file
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\brief A simple example of using non_finite_num facet for
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C99 standard output of infinity and NaN in serialization archives.
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\detail This example shows how to create a C99 non-finite locale,
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and imbue input and output streams with the non_finite_num put and get facets.
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This allow output and input of infinity and NaN in a Standard portable way,
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This permits 'loop-back' of output back into input (and portably across different system too).
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This is particularly useful when used with Boost.Seralization so that non-finite NaNs and infinity
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values in text and xml archives can be handled correctly and portably.
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*/
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#ifdef _MSC_VER
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# pragma warning(disable : 4127) // conditional expression is constant.
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#endif
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#include <boost/archive/text_oarchive.hpp>
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using boost::archive::text_oarchive;
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#include <boost/archive/codecvt_null.hpp>
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using boost::archive::codecvt_null;
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using boost::archive::no_codecvt;
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#include <boost/math/special_functions/nonfinite_num_facets.hpp>
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using boost::math::nonfinite_num_get;
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using boost::math::nonfinite_num_put;
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#include <iostream>
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using std::cout;
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using std::endl;
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using std::cerr;
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#include <iomanip>
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using std::setw;
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using std::left;
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using std::right;
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using std::internal;
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#include <string>
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using std::string;
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#include <sstream>
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using std::istringstream;
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#include <fstream>
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using std::ofstream;
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#include <limits>
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using std::numeric_limits;
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#include <locale>
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using std::locale;
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/*
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Use with serialization archives.
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It is important that the same locale is used
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when an archive is saved and when it is loaded.
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Otherwise, loading the archive may fail.
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By default, archives are saved and loaded with a classic C locale with a
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`boost::archive::codecvt_null` facet added.
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Normally you do not have to worry about that.
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The constructors for the archive classes, as a side-effect,
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imbue the stream with such a locale.
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However, if you want to use the facets `nonfinite_num_put` and `nonfinite_num_get`
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with archives,`then you have to manage the locale manually.
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That is done by calling the archive constructor with the flag `boost::archive::no_codecvt`.
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Then the archive constructor will not imbue the stream with a new locale.
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The following code shows how to use `nonfinite_num_put` with a `text_oarchive`:
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*/
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int main()
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{
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if((std::numeric_limits<double>::has_infinity == false) || (std::numeric_limits<double>::infinity() == 0))
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{
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std::cout << "Infinity not supported on this platform." << std::endl;
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return 0;
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}
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if((std::numeric_limits<double>::has_quiet_NaN == false) || (std::numeric_limits<double>::quiet_NaN() == 0))
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{
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std::cout << "NaN not supported on this platform." << std::endl;
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return 0;
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}
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locale default_locale(locale::classic(), new boost::archive::codecvt_null<char>);
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// codecvt_null so the archive constructor will not imbue the stream with a new locale.
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locale my_locale(default_locale, new nonfinite_num_put<char>);
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// Add nonfinite_num_put facet to locale.
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ofstream ofs("test.txt");
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ofs.imbue(my_locale);
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boost::archive::text_oarchive oa(ofs, no_codecvt);
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double x = numeric_limits<double>::infinity();
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oa & x;
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} // int main()
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/* The same method works with nonfinite_num_get and text_iarchive.
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If you use the trap_infinity and trap_nan flags with a serialization archive,
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then you must set the exception mask of the stream.
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Serialization archives do not check the stream state.
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*/
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