Eric Niebler recently proposed a major TS (https://github.com/ericniebler/range-v3) that aims to refactor STL to introduce ranges. It also breaks compatibility in minor ways (e.g. by allowing for two iterators specifying first and last positions to be of different types), so it will likely be introduced as a new additional library to eventually replace the existing STL, while being very close to compatible. Given that such a rewrite is open to making some changes that break compatibility, are there any other modifications you'd like to see? And what else would you like to see in a C++17 version of STL?

The STL iterator approach as proven very successful for data structures like lists/vectors/tree/etc. Yet for data structures that have a segmented structure such as deque, hash tables, sub-matrices, B-trees, STL has a high abstraction cost for iterators, forcing you to make extra unnecessary checks when comparing two iterators. (see for example Matthew H. Austern's paper "Segmented Iterators and Hierarchical Algorithms": http://lafstern.org/matt/segme...) Do you believe STL should be extended with an additional iterator abstraction to handle such data structures (like Austern's proposed segmented iterators) or do you believe it's too difficult to handle such data structures in a optimal generic way?