[boost] [multiprecision] Bug in double to cpp_bin_float conversion?

13 Apr 2016

      Consider the following code:

#include <boost/multiprecision/cpp_bin_float.hpp>
#include <iostream>

int main()
{
    typedef boost::multiprecision::cpp_bin_float_quad float128_t;

    float128_t f1(1e-9);

    float128_t f2("1e-9");

    std::cout << std::setprecision(std::numeric_limits<float128_t>::max_digits10);

    std::cout << f1 << std::endl;
    std::cout << f2 << std::endl;

    return 0;
}

I'm getting as output:

1.000000000000000062281591457779856419e-09
9.999999999999999999999999999999999325e-10

The conversion of the double literal is not as expected.

On wand box: http://melpon.org/wandbox/permlink/uSGNQZAEEytmb3ao

Is this a bug? If not, what would be the correct way to get my expected behavior?

Thanks,

Rob Conde