AMDG I vote to ACCEPT PFR into Boost. global_ops.hpp/ops.hpp/functions_for.hpp: - Defining functions in a header as static risks UB via the one definition rule. - Can the operators be constexpr? - I don't think that global_ops.hpp is a good idea. `using namespace boost::pfr::ops` in the global namespace achieves almost the same effect and is more clear. - `using namespace boost::pfr::ops` is also quite fragile. It will effectively declare the operators in the global namespace The nearest namespace that encloses both the current scope and the boost::pfr::ops). This means that they will be hidden by any operators defined in the current namespace. For this reason, `using boost::pfr::ops::specific operator` is generally more reliable for functions like comparison operators that tend to be heavily overloaded. #include <boost/pfr/precise/ops.hpp> namespace ns { struct X {}; // Uncommenting this causes a compile error // bool operator<(X, X) { return false; } struct Y {}; void test() { Y y; using namespace boost::pfr::ops; y < y; } } - Does the documentation specify anywhere what operators the struct members need to define in order for the precise operators to work? It looks like the comparison operators require operator== and the operator being defined. - Would it make sense to define operator<=> for C++20? - It would be nice if there were a way to select operators more specifically for BOOST_PFR_FUNCTIONS_FOR. What if I only want the comparision operators and hash, and want to define my own stream operators? - How would I define operators for a class template? detail/fields_count.hpp: - Do ubiq_lref_constructor and ubiq_rref_constructor need to have their conversion operators defined? If they were only declared they wouldn't need to use unsafe_declval. ----------------- - The error when a struct has an array member is not very informative. I can't think of a good way to detect this, however. - It would also be nice if there were a trait that covers all the detectable modes of failure, or perhaps a macro that has all the static asserts in fields_count. - The reference docs often uses it's instead of its: its = possessive pronoun it's = contraction of it is In Christ, Steven Watanabe