workaround.cpp

template<class F>
concept mutable_value_visitor =
    requires(F f, value& v)
    {
        { f(v) };
    };

template < mutable_value_visitor Visitor >
void
enumerate(value &v, Visitor f)
{
    switch (v.kind())
    {
    case kind::null:
    case kind::bool_:
    case kind::int64:
    case kind::uint64:
    case kind::double_:
    case kind::string:
        f(v);
        break;

    case kind::array:
        for (auto &entry : v.as_array())
            enumerate(entry, f);
        break;

    case kind::object:
        for (auto &entry : v.as_object())
            enumerate(entry.value(), f);
        break;
    }
}

void
rectify_floats(value &v, double precision = 9)
{
    auto op = [precision](value &x) {
        if (auto d = x.if_double())
        {
            auto scale       = std::floor(std::log10(*d));
            auto rounding    = std::pow(10.0, scale - precision);
            *d = std::round(*d / rounding) * rounding;
        }
    };

    enumerate(v, op);
}