I see this in the commit log for boost.filesystem: Deprecated path construction/assignment/appending from container types. Users are advised to use string types and iterators instead of containers to construct/assign/append to paths. In v4, the support for containers is removed. This can't be right now, can it? Because std::filesystem supports path construction from anything meeting the requirements of Source which is kind of range-like. Boost.URL and its downstream libraries HTTP-Proto, HTTP-IO, Websocket-Proto, and Websocket-IO are depending on the container-based interface to achieve reasonably decent syntax and semantics despite the limitations of the path API (which are the fault of the standard and not Boost). If std::filesystem::path supports container-based parameters to assign() and append() then why is boost::filesystem::path removing it? Thanks