https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116399
--- Comment #8 from 康桓瑋 <hewillk at gmail dot com> --- (In reply to Jonathan Wakely from comment #7) > "Note that this view is not common_range because it can be implemented more > efficiently > without that requirement, and, being copyable, it can be adapted into one." > > and > > "We found that aliases can be efficiently stored and looked up in a sorted > list of alias/mib pairs. Making a common_range of aliases_view would force > an implementation to find the end of the list of aliases for a particular > encoding, which is slightly efficient than what is possible, so this is not > proposed. Mostly, we found little use for it to be a common_range." If so, why not just explicitly specify that end() returns std::default_sentinel? libstdc++'s _Sentinel is just an empty class, so there is no need to introduce an additional class IMO.
