gistfile1.txt

template<class T>
T
number_cast(value const& jv, error_code& ec) noexcept
{
    T result{};

    if(! jv.is_number())
    {
        ec = error::not_number;
        return result;
    }

    switch(jv.kind())
    {
    case kind::double_:
        result = static_cast<T>(
            jv.get_double());
        if(result != jv.get_double())
        {
            ec = error::not_exact;
            return result;
        }
        break;

    case kind::int64:
        result = static_cast<T>(
            jv.get_int64());
        if(result != jv.get_int64())
        {
            ec = error::not_exact;
            return result;
        }
        break;

    case kind::uint64:
        result = static_cast<T>(
            jv.get_uint64());
        if(result != jv.get_uint64())
        {
            ec = error::not_exact;
            return result;
        }
        break;
    }

    return result;
}