Class NA

tensorflow/core/lib/gtl/flatmap_test.cc:465–471

Non-assignable values should work.

// Non-assignable values should work.
struct NA {
  int64 value;
  NA() : value(-1) {}
  explicit NA(int64 v) : value(v) {}
  NA(const NA& x) : value(x.value) {}
  bool operator==(const NA& x) const { return value == x.value; }
};
struct HashNA {
  size_t operator()(NA x) const { return x.value; }
};