Why Strings as Classes? [C++ iterator]

[Fawzi Mohamed]

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