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libs/math/example/nonfinite_serialization_archives.cpp

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