C++ / Why Iterators Got It All Wrong

Robert M. Münch via Digitalmars-d digitalmars-d at puremagic.com
Sat Sep 2 13:22:44 PDT 2017

On 2017-09-01 20:34:32 +0000, Mark said:

> On Tuesday, 29 August 2017 at 12:50:08 UTC, Robert M. Münch wrote:
>> Maybe of interest: https://www.think-cell.com/en/career/talks/iterators/#1
>> I haven't read everything, so not sure if it worth to take a look.
> Iterators have many problems. Andrei's talk some years ago, titled 
> "Iterators Must Go", points out many of them in a clear fashion. I 
> think most of the problems stem from the fact that they are inherently 
> a leaky abstraction. Iterators basically treat all data structures as a 
> singly/doubly linked list or as arrays (if they allow random access). 
> There is no natural or intuitive way of describing, say, a tree or an 
> arbitrary graph as a list/array. Ranges and cursors try to solve some 
> of the issues but they still have this fundamental problem.

Iterators are not the silver bullet. But IIRC you can specify if you 
want to iterate over a graph BF or DF. If you just need to "iterate" 
over the elements things work pretty good IMO. If you want to select a 
sub-set and then iterate things get much complicater anyway.

> It may be unrealisic to expect such a nice abstraction of iteration for 
> other data structures, not to mention a universal one which will work 
> for all interesting data structures.

That's true, hence I didn't ever expected this at all. Some pretty 
simple & basic building blocks and the rest is done on-demand fitting 
the use-case.

Robert M. Münch
smarter | better | faster

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