A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4006

Date: 2014-05-26

An improved emplace() for unique-key maps

by Thomas Köppe

Excerpt:

The author had initially proposed in N3873 to add new specialised algorithms to unique-key maps, ... When that paper was presented in Issaquah in February 2014, Jeffrey Yasskin created LWG 2362 to track the core problem, namely the lack of specification of whether moving-from happens. At the meeting, there seems to have been a strong consensus that emplace should “just work”, but that no progress could be made until a concrete proposal had been worked out. At the same time, new algorithms should not be added, and a fixed emplace would provide the desired functionality. It was also recognized that fixing emplace would not be trivial and that there would need to be a way to extract the key from the arguments.