Class adder

include/boost/histogram/storage/adaptive_storage.hpp:226–290

};

struct adder {
  template <typename U>
  using is_convertible_to_mp_int = typename std::is_convertible<U, mp_int>::type;

  template <typename U>
  using is_integral = typename std::is_integral<U>::type;

  template <typename T, typename Buffer, typename U>
  void if_integral(std::true_type, T* tp, Buffer& b, std::size_t i, const U& x) {
    if (!safe_radd(tp[i], x)) {
      using V = next_type<T>;
      create(type_tag<V>(), b, tp);
      destroyer()(tp, b);
      operator()(reinterpret_cast<V*>(b.ptr), b, i, x);
    }
  }

  template <typename T, typename Buffer, typename U>
  void if_integral(std::false_type, T* tp, Buffer& b, std::size_t i, const U& x) {
    create(type_tag<wcount>(), b, tp);
    destroyer()(tp, b);
    operator()(reinterpret_cast<wcount*>(b.ptr), b, i, x);
  }

  template <typename T, typename Buffer, typename U>
  void operator()(T* tp, Buffer& b, std::size_t i, const U& x) {
    if_integral(is_integral<U>(), tp, b, i, x);
  }

  template <typename Buffer, typename U>
  void operator()(void*, Buffer& b, std::size_t i, const U& x) {
    using V = next_type<void>;
    create(type_tag<V>(), b);
    operator()(reinterpret_cast<V*>(b.ptr), b, i, x);
  }

  template <typename Buffer, typename U>
  void if_convertible_to_mp_int(std::true_type, mp_int* tp, Buffer&, std::size_t i,
                                const U& x) {
    tp[i] += static_cast<mp_int>(x);
  }

  template <typename Buffer, typename U>
  void if_convertible_to_mp_int(std::false_type, mp_int* tp, Buffer& b, std::size_t i,
                                const U& x) {
    create(type_tag<wcount>(), b, tp);
    destroyer()(tp, b);
    operator()(reinterpret_cast<wcount*>(b.ptr), b, i, x);
  }

  template <typename Buffer, typename U>
  void operator()(mp_int* tp, Buffer& b, std::size_t i, const U& x) {
    if_convertible_to_mp_int(is_convertible_to_mp_int<U>(), tp, b, i, x);
  }

  template <typename Buffer, typename U>
  void operator()(wcount* tp, Buffer&, std::size_t i, const U& x) {
    tp[i] += x;