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From: Roy Smith on 15 Jun 2010 22:55
In article <btudnbk1N85t74rRnZ2dnUVZ7vudnZ2d(a)giganews.com>,
"Leigh Johnston" <leigh(a)i42.co.uk> wrote:

> The only valid operations on an invalid iterator are initialization and
> assignment

Well, to pick a nit, there's a third. You can destruct it :-)

It's actually not that much of a nit. Letting an object get into a
state where it cannot be safely destructed is rather rude, and something
to be avoided in polite company.

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From: Stuart Golodetz on 17 Jun 2010 03:52
Daniel Kr�gler wrote:
> On 15 Jun., 11:16, Peng Yu <pengyu...(a)gmail.com> wrote:
>> Suppose I have an std::vector<int>::iterator that I get from somewhere
>> else. I'm not sure if it is properly initialized. Is there a way to
>> test in runtime?
>
> There does not exist a general test function for this. This
> is so, because pointers are iterators and there also exists
> no general/portable mechanism to verify whether a pointer
> value is valid:
>
> int main() {
> int* p, q; // not initialized

Not that it in any way obscures the point, but ITYM:

int *p, *q;

Regards,
Stu

> if (p == q) ; // Undefined behaviour
> }
>
> HTH & Greetings from Bremen,
>
> Daniel Kr�gler


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From: Helge Kruse on 18 Jun 2010 00:30

"Daniel Kr�gler" <daniel.kruegler(a)googlemail.com> wrote in message
news:386bf185-b973-405f-bc33-bbc8d0696a25(a)x27g2000yqb.googlegroups.com...
> int main() {
> int* p, q; // not initialized
> if (p == q) ; // Undefined behaviour
> }

No. It's "defined behaviour". The compiler will not allow to compare an
integer and a pointer to integer. ;-)

Helge



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