https://svn.boost.org/trac10/ticket/9545 <p> When setting the default value of a float option to 0.05, the help description that is printed by the program states that the default value is 0.0500000007. For double, it states "0.050000000000000003". The value of the variable within the program is correct, i.e. 0.05. </p> <p> I'm compiling with: </p> <p> $ g++ --version g++ (GCC) 4.8.3 20131226 (prerelease) </p> <p> Here is a test program that reproduces the problem when run with the option "--help": </p> <pre class="wiki">#include "boost/program_options.hpp" int main(int argc, char ** argv) { float dt; boost::program_options::variables_map vm; boost::program_options::options_description desc("Description"); desc.add_options() ("help", "Print help message") ("dt", boost::program_options::value&lt;float&gt;(&amp;dt)-&gt;default_value(0.05), "Time step") ; boost::program_options::store(boost::program_options::parse_command_line(argc, argv, desc), vm); boost::program_options::notify(vm); if(vm.count("help")) desc.print(std::cout); std::cout &lt;&lt; "dt = " &lt;&lt; dt &lt;&lt; "\n"; return 0; } </pre> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/9545 Trac 1.4.3 Vladimir Prus Tue, 07 Jan 2014 16:24:16 GMT