Function EmptyReference

tests/cpp/common/test_quantile.h:460–460

inline std::size_t UniqueValueCount(ReferenceColumn const& col) { return col.values.size(); }

inline bool EmptyReference(ReferenceColumn const& col) { return col.values.empty(); }

inline Span<float const> ExactValues(ReferenceColumn const& col) {
  return {col.values.data(), col.values.size()};