/** lexical_cast_nonfinite_facets.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' with lexical cast * to obtain C99 representation of infinity and NaN. * This example is 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 very simple example of using lexical cast with non_finite_num facet for C99 standard output of infinity and NaN. \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 allows lexical_cast 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). */ #include <boost/math/special_functions/nonfinite_num_facets.hpp> using boost::math::nonfinite_num_get; using boost::math::nonfinite_num_put; #include <boost/lexical_cast.hpp> using boost::lexical_cast; #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 <limits> using std::numeric_limits; #include <locale> using std::locale; #include <boost/assert.hpp> int main () { std::cout << "lexical_cast example (NOT using finite_num_facet)." << std::endl; 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; } // Some tests that are expected to fail on some platforms. // (But these tests are expected to pass using non_finite num_put and num_get facets). // Use the current 'native' default locale. std::locale default_locale (std::locale::classic ()); // Note the currrent (default C) locale. // Create plus and minus infinity. double plus_infinity = +std::numeric_limits<double>::infinity(); double minus_infinity = -std::numeric_limits<double>::infinity(); // and create a NaN (NotANumber). double NaN = +std::numeric_limits<double>::quiet_NaN (); // Output the nonfinite values using the current (default C) locale. // The default representations differ from system to system, // for example, using Microsoft compilers, 1.#INF, -1.#INF, and 1.#QNAN. cout << "Using default locale" << endl; cout << "+std::numeric_limits<double>::infinity() = " << plus_infinity << endl; cout << "-std::numeric_limits<double>::infinity() = " << minus_infinity << endl; cout << "+std::numeric_limits<double>::quiet_NaN () = " << NaN << endl; // Checks below are expected to fail on some platforms! // Now try some 'round-tripping', 'reading' "inf" double x = boost::lexical_cast<double>("inf"); // and check we get a floating-point infinity. BOOST_ASSERT(x == std::numeric_limits<double>::infinity()); // Check we can convert the other way from floating-point infinity, string s = boost::lexical_cast<string>(numeric_limits<double>::infinity()); // to a C99 string representation as "inf". BOOST_ASSERT(s == "inf"); // Finally try full 'round-tripping' (in both directions): BOOST_ASSERT(lexical_cast<double>(lexical_cast<string>(numeric_limits<double>::infinity())) == numeric_limits<double>::infinity()); BOOST_ASSERT(lexical_cast<string>(lexical_cast<double>("inf")) == "inf"); return 0; } // int main() /* Output: from MSVC 10, fails (as expected) lexical_cast_native.vcxproj -> J:\Cpp\fp_facet\fp_facet\Debug\lexical_cast_native.exe lexical_cast example (NOT using finite_num_facet). Using default locale +std::numeric_limits<double>::infinity() = 1.#INF -std::numeric_limits<double>::infinity() = -1.#INF +std::numeric_limits<double>::quiet_NaN () = 1.#QNAN 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" C:\Program Files\MSBuild\Microsoft.Cpp\v4.0\Microsoft.CppCommon.targets(183,5): error MSB3073: :VCEnd" exited with code 3. */