Operator overloading

[Bill Baxter]

On Sat, Dec 27, 2008 at 11:19 PM, Jarrett Billingsley
<jarrett.billingsley at gmail.com> wrote:
> On Sat, Dec 27, 2008 at 2:31 AM, Andrei Alexandrescu
> <SeeWebsiteForEmail at erdani.org> wrote:
>>>> For iterators, increment is quite different from
>>>> addition of an arbitrary number, so what D managed to do was effectively
>>>> to
>>>> cripple iterators. The standard library will use ranges with named
>>>> functions
>>>> so it avoids the issue, but if someone wants to define STL-style
>>>> iterators
>>>> they won't be able to.
>>>
>>> I suppose most people who _aren't_ coming from C++ (*cough* like me
>>> *cough*) won't be terribly unhappy about this situation.
>>
>> I'm not sure how that computes. The particular notion has little to do with
>> C++ and is rather fundamental, so not grokking it should motivate one to
>> look into it (as opposed to being glad for not knowing).
>
> I got the impression from your argument that you thought that without
> an appropriate method of overloading the increment operator, it's not
> possible to duplicate the _syntax_ of STL-style iterators.  My
> response is - who cares?  I don't think of iterators as "pointers that
> can be incremented," and I doubt anyone who doesn't have a C++
> background thinks of them that way either.  It seems that the
> semantics of STL iterators can be implemented with methods just as
> well.

There is a little something nice about being able to use a pointer and
iterator interchangeably for templated container algorithms.  You lose
that if ++iter can't be used to iterate your iterator.  But working
around it is not really that hard.  One little incr(T)(ref thing)
template and you're pretty much done.  But ++foo is a concise syntax
that conveys the meaning of what's happening pretty well, so it's a
shame not to be able to use it on iterators.
(Actually I don't really recall why it can't be used for iterators in
D other than it forces you to use more runtime errors for bad args to
+=.  Was there anything more to it than that?)

--bb