boost::pfr::less_equal — std::less_equal like comparator that returns boost::pfr::le (x, y)
// In header: <boost/pfr/functors.hpp> template<typename T> struct less_equal { // public member functions (, ) ; };
less_equal
( x, y) ;
Returns:
true if field of x less than the field with same index of y and all previous fields of x equal to the same fields of y; or if each field of x equals the field with same index of y.