Sorting a zipped range

[Timon Gehr]

On 02/27/2014 10:09 PM, Ben Jones wrote:
>
> My question is:  which features of the D range abstraction allow zip to
> work the way we expect?

Assignable elements of a range do not need to be addressable.

> What C++isms were left behind to make this work?

In C++, iterators should implement operator-> which must return a 
pointer to  data, and unary operator*, which should return a reference 
if it is to be assignable. This makes the iterator abstraction less 
flexible.

I.e. it is a consequence of

- desire to use pointer-like syntax for iterators
- weak support for hooking into the corresponding syntactic constructs

Phobos eg. allows retrieval of and assignment to a range's front element 
to be implemented in distinct methods that can execute arbitrary code. 
Zip uses such facilities to distribute assignments to its range elements 
back to each source range.