【bug】 tools.cpp-num_fractions_from_double_type

[tianjixuetu]

std::size_t num_fractions_from_double_type(const double_type &v) {
        if (v == 1) return 1u;

        double_type r{v};
        std::size_t n = 0u;
        for (; r != 1; ++n) {
            r *= 10;
        }

        return n;
}

in the code, r!=1, it makes the for loop will continue forever if v!=1;