Ranges TS breaking changes?

Question

It is said that the injection of the Ranges TS into the std namespace would cause a number of breaking changes to the standard library (e.g. this link). Does anybody know what those changes are?

Answer 1

From N4569 Annex B (as linked by @Holt in the comments above):

• Algorithm Return Types -- modified to include the end iterator

• Stronger Constraints -- algorithms that used to require just < now require all comparison operators

• Constrained Functional Objects -- Constraints added to std::less's type and the like.

• Iterators and Default-Constructibility -- Ranges_v3 assumes iterators can be default constructed (in a useful way). This is not currently required.

• iterator_traits cannot be specialized -- in Range_v3, it is an alias template.

• N3351 -- it is also incompatible with the N3351 proposal in a number of ways, which I won't get into here.

This is just a summary. Follow the link to the paper or find it for more details.