template<class F>
void
number::
assign(F v
    ,typename std::enable_if<
        std::is_floating_point<
        F>::value>::type*) noexcept
{
    static exponent_type const bias =
        static_cast<exponent_type>(std::floor(
            std::log10((std::numeric_limits<
                mantissa_type>::max)()))) - 2;
    if(v < 0)
    {
        v = std::abs(v);
        neg_ = true;
    }
    else
    {
        neg_ = false;
    }
    exp_ = static_cast<exponent_type>(
        std::floor(std::log10(v))) - bias;
    mant_ = static_cast<mantissa_type>(
        v / std::pow(10, exp_));
    normalize();
}