Boost C++ Libraries

boost::cnv::charconv cnv;

BOOST_TEST(  "-3.14159" == convert<string>(-3.14159, cnv(arg::notation = cnv::notation::fixed)(arg::precision = 5)).value());
BOOST_TEST("-3.142e+00" == convert<string>(-3.14159, cnv(arg::notation = cnv::notation::scientific)(arg::precision = 3)).value());
BOOST_TEST("-1.9220p+1" == convert<string>(-3.14159, cnv(arg::notation = cnv::notation::hex)(arg::precision = 4)).value());