Conversion from valarray<double> to json fails to build

[popizdeh]

There seems to be a regression from 2.0.8 and 2.1.1. This no longer compiles.

std::valarray<double> v;
nlohmann::json j;
j["test"] = v;

P.S. Is there any chance we can get a release with std::vector fix released?

[theodelrieu]

Oops, this is due to the has_iterator traits that check for a iterator type alias, which valarray doesn't provide. Sorry about that.

namespace nlohmann
{
template <typename T>
struct adl_serializer<std::valarray<T>>
{
  static void to_json(json &j, std::valarray<T> const &v)
  {
    detail::external_constructor<detail::value_t::array>::construct(j, v);
  }

  static void from_json(json const &j, std::valarray<T> &v)
  {
    // checks omitted, not the best implem, never played with valarray myself
    auto arr = j.get<std::vector<T>>();
    v = std::valarray<T>(arr.data(), arr.size());
  }
};
}

As for the bug fix release, I don't know what @nlohmann thinks about it.

[nlohmann]

We need to fix this and add std::valarray support for the 3.x.x release. I did not plan to create a bug fix release for this.

[nlohmann]

Fixed with 9fd031b.