Why Strings as Classes? [C++ iterator]

[Fawzi Mohamed]

On 2008-08-28 11:47:22 +0200, Fawzi Mohamed <fmohamed at mac.com> said:

> On 2008-08-28 00:24:50 +0200, Dee Girl <deegirl at noreply.com> said:
> 
>> Derek Parnell Wrote:
>> 
>>> On Wed, 27 Aug 2008 17:08:47 -0400, Nick Sabalausky wrote:
>>> 
>>>> The way I see it, encapsulation is all about the black box idea. And the
>>>> only things you can see from outside the black box are the inputs and
>>>> outputs.
>>> 
>>> Well said.
>> 
>> I am sorry I will say my opinion. This sounds good but is simplistic. 
>> Black box is good in principle. But it assume you found right interface 
>> for the black box. If you define bad interface you have a bad black 
>> box. Also please remember that iterator is black box also. But it 
>> defines right interface.
> 
> I agree with the meaning, but I disagree with the example.
> I think that iterators are an example of bad interface, as also others 
> brought up the iterator as good example I though that I should say 
> something.
> 
> An iterator should be like a generator, have a method next, and one 
> at_end or something similar packaged (and maybe prev() and at_start() 
> if it can also go back) in a single struct, furthermore it should work 
> seamlessly with a kind of for_each(x;iterator) construct.
> 
> Instead C++ choose to have begin & end iterators, simply because with 
> that construct it is trivial for the compiler to optimize it for 
> arrays, and you can use pointers as iterators without a 
> cast/constructor.
> 
> This means a worse interface for 99% of the uses, apart form arrays and 
> vectors I think one is better off without end iterator, and even when 
> this is not the case writing something like for_each(x;FromTo(a,b)), 
> with FromTo constructing a generator is (I think) better than 
> for(i=t.begin();i!=t.end();++t), and the implementation of an a 
> generator itself is easier (no ==,!=,increment, decrement(pre/post),... 
> for performance reasons)
> 
> As I believe that the optimizations to make the better interface be as 
> efficient as the iterator one are perfectly doable (some work, yes, but 
> not extremely much so), I see no good reason for C++ design.
> 
> Fawzi

Please note before the discussion gets messy, that I find the hierarchy 
and kinds of iterators in c++ well done, (input,output,...random), but 
the interface of them (especially the most used) flawed.