ceph/src/boost/libs/math/example/lexical_cast_native.cpp

   1 /** lexical_cast_nonfinite_facets.cpp
   2 *
   3 * Copyright (c) 2011 Paul A. Bristow
   4 *
   5 * Distributed under the Boost Software License, Version 1.0.
   6 * (See accompanying file LICENSE_1_0.txt
   7 * or copy at http://www.boost.org/LICENSE_1_0.txt)
   8 *
   9 * This very simple program illustrates how to use the
  10 * `boost/math/nonfinite_num_facets.hpp' with lexical cast
  11 * to obtain C99 representation of infinity and NaN.
  12 * This example is from the original Floating Point  Utilities contribution by Johan Rade.
  13 * Floating Point Utility library has been accepted into Boost,
  14 * but the utilities are incorporated into Boost.Math library.
  15 *
  16 \file
  17
  18 \brief A very simple example of using lexical cast with
  19 non_finite_num facet for C99 standard output of infinity and NaN.
  20
  21 \detail This example shows how to create a C99 non-finite locale,
  22 and imbue input and output streams with the non_finite_num put and get facets.
  23 This allows lexical_cast output and input of infinity and NaN in a Standard portable way,
  24 This permits 'loop-back' of output back into input (and portably across different system too).
  25
  26 */
  27
  28 #include <boost/math/special_functions/nonfinite_num_facets.hpp>
  29 using boost::math::nonfinite_num_get;
  30 using boost::math::nonfinite_num_put;
  31
  32 #include <boost/lexical_cast.hpp>
  33 using boost::lexical_cast;
  34
  35 #include <iostream>
  36 using std::cout;
  37 using std::endl;
  38 using std::cerr;
  39
  40 #include <iomanip>
  41 using std::setw;
  42 using std::left;
  43 using std::right;
  44 using std::internal;
  45
  46 #include <string>
  47 using std::string;
  48
  49 #include <sstream>
  50 using std::istringstream;
  51
  52 #include <limits>
  53 using std::numeric_limits;
  54
  55 #include <locale>
  56 using std::locale;
  57
  58 #include <boost/math/tools/assert.hpp>
  59
  60 int main ()
  61 {
  62   std::cout << "lexical_cast example (NOT using finite_num_facet)." << std::endl;
  63
  64   if((std::numeric_limits<double>::has_infinity == false) || (std::numeric_limits<double>::infinity() == 0))
  65   {
  66     std::cout << "Infinity not supported on this platform." << std::endl;
  67     return 0;
  68   }
  69
  70   if((std::numeric_limits<double>::has_quiet_NaN == false) || (std::numeric_limits<double>::quiet_NaN() == 0))
  71   {
  72     std::cout << "NaN not supported on this platform." << std::endl;
  73     return 0;
  74   }
  75
  76   // Some tests that are expected to fail on some platforms.
  77   // (But these tests are expected to pass using non_finite num_put and num_get facets).
  78
  79   // Use the current 'native' default locale.
  80   std::locale default_locale (std::locale::classic ()); // Note the current (default C) locale.
  81
  82   // Create plus and minus infinity.
  83   double plus_infinity = +std::numeric_limits<double>::infinity();
  84   double minus_infinity = -std::numeric_limits<double>::infinity();
  85
  86   // and create a NaN (NotANumber).
  87   double NaN = +std::numeric_limits<double>::quiet_NaN ();
  88
  89   // Output the nonfinite values using the current (default C) locale.
  90   // The default representations differ from system to system,
  91   // for example, using Microsoft compilers, 1.#INF, -1.#INF, and 1.#QNAN.
  92   cout << "Using default locale" << endl;
  93   cout << "+std::numeric_limits<double>::infinity() = " << plus_infinity << endl;
  94   cout << "-std::numeric_limits<double>::infinity() = " << minus_infinity << endl;
  95   cout << "+std::numeric_limits<double>::quiet_NaN () = " << NaN << endl;
  96
  97   // Checks below are expected to fail on some platforms!
  98
  99   // Now try some 'round-tripping', 'reading' "inf"
 100   double x = boost::lexical_cast<double>("inf");
 101   // and check we get a floating-point infinity.
 102   BOOST_MATH_ASSERT(x == std::numeric_limits<double>::infinity());
 103
 104   // Check we can convert the other way from floating-point infinity,
 105   string s = boost::lexical_cast<string>(numeric_limits<double>::infinity());
 106   // to a C99 string representation as "inf".
 107   BOOST_MATH_ASSERT(s == "inf");
 108
 109   // Finally try full 'round-tripping' (in both directions):
 110   BOOST_MATH_ASSERT(lexical_cast<double>(lexical_cast<string>(numeric_limits<double>::infinity()))
 111     == numeric_limits<double>::infinity());
 112   BOOST_MATH_ASSERT(lexical_cast<string>(lexical_cast<double>("inf")) == "inf");
 113
 114   return 0;
 115 } // int main()
 116
 117 /*
 118
 119 Output:
 120
 121 from MSVC 10, fails (as expected)
 122
 123   lexical_cast_native.vcxproj -> J:\Cpp\fp_facet\fp_facet\Debug\lexical_cast_native.exe
 124   lexical_cast example (NOT using finite_num_facet).
 125   Using default locale
 126   +std::numeric_limits<double>::infinity() = 1.#INF
 127   -std::numeric_limits<double>::infinity() = -1.#INF
 128   +std::numeric_limits<double>::quiet_NaN () = 1.#QNAN
 129 C:\Program Files\MSBuild\Microsoft.Cpp\v4.0\Microsoft.CppCommon.targets(183,5): error MSB3073: The command ""J:\Cpp\fp_facet\fp_facet\Debug\lexical_cast_native.exe"
 130 C:\Program Files\MSBuild\Microsoft.Cpp\v4.0\Microsoft.CppCommon.targets(183,5): error MSB3073: :VCEnd" exited with code 3.
 131
 132
 133 */