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Diffstat (limited to 'src/boost/libs/math/example/lexical_cast_native.cpp')
-rw-r--r-- | src/boost/libs/math/example/lexical_cast_native.cpp | 133 |
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diff --git a/src/boost/libs/math/example/lexical_cast_native.cpp b/src/boost/libs/math/example/lexical_cast_native.cpp new file mode 100644 index 00000000..aaee6b5d --- /dev/null +++ b/src/boost/libs/math/example/lexical_cast_native.cpp @@ -0,0 +1,133 @@ +/** 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. + + +*/ |