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All macros of the type BOOST_FLOAT16_C, BOOST_FLOAT32_C, BOOST_FLOAT64_C, BOOST_FLOAT80_C, BOOST_FLOAT128_C,
and BOOST_FLOATMAX_C
are always defined after inclusion of <boost/cstdfloat.hpp>
.
These allow floating-point constants of at least the specified width to be declared:
// Declare Archimedes' constant using float32_t with approximately 7 decimal digits of precision. static const boost::float32_t pi = BOOST_FLOAT32_C(3.1415926536); // Declare the Euler-gamma constant with approximately 15 decimal digits of precision. static const boost::float64_t euler = BOOST_FLOAT64_C(0.57721566490153286060651209008240243104216); // Declare the Golden Ratio constant with the maximum decimal digits of precision that the platform supports. static const boost::floatmax_t golden_ratio = BOOST_FLOATMAX_C(1.61803398874989484820458683436563811772);
Tip | |
---|---|
Boost.Math provides many constants 'built-in', so always use Boost.Math constants if available, for example: |
// Display the constant pi to the maximum available precision. boost::floatmax_t pi_max = boost::math::constants::pi<boost::floatmax_t>(); std::cout.precision(std::numeric_limits<boost::floatmax_t>::digits10); std::cout << "Most precise pi = " << pi_max << std::endl; // If floatmax_t is float_128_t, then // Most precise pi = 3.141592653589793238462643383279503
from cstdfloat_example.cpp.
See the complete list of constants.