cpp/filesystem/directory iterator

is a that iterates over the  elements of a directory (but does not visit the subdirectories). The iteration order is unspecified, except that each directory entry is visited only once. The special pathnames and  are skipped.

If the reports an error or is advanced past the last directory entry, it becomes equal to the default-constructed iterator, also known as the end iterator. Two end iterators are always equal, dereferencing or incrementing the end iterator is undefined behavior.

If a file or a directory is deleted or added to the directory tree after the directory iterator has been created, it is unspecified whether the change would be observed through the iterator.

Non-member functions
Additionally, provided as required by.

It is unspecified whether an equality operator is a member or non-member.

Helper templates
These specializations for make it a  and a.