Dereferencing (pointer to) iterator

[xgngli]

Suppose we have a vector:
vector<intvec(1 0);

We can declare a iterator this way:
vector<int>::it erator vecItor;

and then dereference it like this:
for (vecItor = vec.begin(); vecItor != vec.end(); vecItor++)
{
cout << *vecItor << endl;
}

But how can we dereference the iterator if we declare it this way:
vector<int>::it erator* vecItor;

(I need to declare the iterator the second way since I'm declaring it
under a managed C++ class.)

Thanks!

[Victor Bazarov]

xg****@gmail.co m wrote:

Suppose we have a vector:
vector<intvec(1 0);

We can declare a iterator this way:
vector<int>::it erator vecItor;

and then dereference it like this:
for (vecItor = vec.begin(); vecItor != vec.end(); vecItor++)
{
cout << *vecItor << endl;
}

But how can we dereference the iterator if we declare it this way:
vector<int>::it erator* vecItor;

(I need to declare the iterator the second way since I'm declaring it
under a managed C++ class.)

What's wrong with **vecItor?

V
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[Andre Kostur]

"xg****@gmail.c om" <xg****@gmail.c omwrote in
news:11******** **************@ z28g2000prd.goo glegroups.com:

Suppose we have a vector:
vector<intvec(1 0);

We can declare a iterator this way:
vector<int>::it erator vecItor;

and then dereference it like this:
for (vecItor = vec.begin(); vecItor != vec.end(); vecItor++)
{
cout << *vecItor << endl;
}

But how can we dereference the iterator if we declare it this way:
vector<int>::it erator* vecItor;

**vecItor.

That's a pointer-to-iterator. So you need to dereference your pointer
part, then dereference the iterator.

[xgngli]

On Jun 22, 6:04 pm, Andre Kostur <nntps...@kostu r.netwrote:

"xgn...@gmail.c om" <xgn...@gmail.c omwrote innews:11****** *************** *@z28g2000prd.g ooglegroups.com :

Suppose we have a vector:
vector<intvec(1 0);

We can declare a iterator this way:
vector<int>::it erator vecItor;

and then dereference it like this:
for (vecItor = vec.begin(); vecItor != vec.end(); vecItor++)
{
cout << *vecItor << endl;
}

But how can we dereference the iterator if we declare it this way:
vector<int>::it erator* vecItor;

**vecItor.

That's a pointer-to-iterator. So you need to dereference your pointer
part, then dereference the iterator.

Thanks guys. That makes perfect sense. However, when I run this in
Visual Studio,

vector<intvec(1 0);
vector<int>::it erator* vecItor = new vector<int>::it erator();

for (*vecItor = vec.begin(); *vecItor != vec.end(); vecItor++)
{
cout << **vecItor << endl;
}

it caused debug assertion failure: vector iterators incompatible.

So I suspect there is no problem with the grammar. I just need to
search somewhere else to
find a way making VS happy.

[Jim Langston]

<xg****@gmail.c omwrote in message
news:11******** **************@ k79g2000hse.goo glegroups.com.. .

On Jun 22, 6:04 pm, Andre Kostur <nntps...@kostu r.netwrote:

>"xgn...@gmail. com" <xgn...@gmail.c omwrote
innews:11***** *************** **@z28g2000prd. googlegroups.co m:

Suppose we have a vector:
vector<intvec(1 0);

We can declare a iterator this way:
vector<int>::it erator vecItor;

and then dereference it like this:
for (vecItor = vec.begin(); vecItor != vec.end(); vecItor++)
{
cout << *vecItor << endl;
}

But how can we dereference the iterator if we declare it this way:
vector<int>::it erator* vecItor;

**vecItor.

That's a pointer-to-iterator. So you need to dereference your pointer
part, then dereference the iterator.

Thanks guys. That makes perfect sense. However, when I run this in
Visual Studio,

vector<intvec(1 0);
vector<int>::it erator* vecItor = new vector<int>::it erator();

You declared a pointer to an iterator, yet you haven't pointed it to
anything yet. It's pointing to random memory since it's uninitialized. I
do not know if:
vecItor = new( std:vector<int> ::iterator );
is legal or not. It may be, I just don't know (have never tried to new a
template before).

for (*vecItor = vec.begin(); *vecItor != vec.end(); vecItor++)

You are using some memory, which your program probably doesn't own, as an
interator. Also, you are incrementing the pointer with vecItor++, did you
mean *vecItor++ (that is, once you actually have it pointing to some memory
set aside as an interator).

{
cout << **vecItor << endl;
}

it caused debug assertion failure: vector iterators incompatible.

So I suspect there is no problem with the grammar. I just need to
search somewhere else to
find a way making VS happy.

[Kai-Uwe Bux]

xg****@gmail.co m wrote:

On Jun 22, 6:04 pm, Andre Kostur <nntps...@kostu r.netwrote:

>"xgn...@gmail. com" <xgn...@gmail.c omwrote
innews:11***** *************** **@z28g2000prd. googlegroups.co m:

Suppose we have a vector:
vector<intvec(1 0);

We can declare a iterator this way:
vector<int>::it erator vecItor;

and then dereference it like this:
for (vecItor = vec.begin(); vecItor != vec.end(); vecItor++)
{
cout << *vecItor << endl;
}

But how can we dereference the iterator if we declare it this way:
vector<int>::it erator* vecItor;

**vecItor.

That's a pointer-to-iterator. So you need to dereference your pointer
part, then dereference the iterator.

Thanks guys. That makes perfect sense. However, when I run this in
Visual Studio,

vector<intvec(1 0);
vector<int>::it erator* vecItor = new vector<int>::it erator();

for (*vecItor = vec.begin(); *vecItor != vec.end(); vecItor++)

for ( *vecItor = vec.begin(); *vecItor != vec.end(); ++ *vecItor )

However: I have a very hard time to belive that you have a valid reason to
use an iterator* instead of an iterator here. It looks just insane.

{
cout << **vecItor << endl;
}

it caused debug assertion failure: vector iterators incompatible.

So I suspect there is no problem with the grammar. I just need to
search somewhere else to
find a way making VS happy.

Best

Kai-Uwe Bux

[Thomas J. Gritzan]

Jim Langston wrote:

<xg****@gmail.c omwrote...

>vector<intvec( 10);
vector<int>::i terator* vecItor = new vector<int>::it erator();

You declared a pointer to an iterator, yet you haven't pointed it to
anything yet.

The OP sets the pointer to new'd memory, so that's no problem. The iterator
itself points to nowhere, but gets assigned in the for loop:
*vecItor = vec.begin();
Also ok here.

It's pointing to random memory since it's uninitialized. I
do not know if:
vecItor = new( std:vector<int> ::iterator );
is legal or not. It may be, I just don't know (have never tried to new a
template before).

iterator is a typedef inside a template class, so why shouldn't it be legal?

>for (*vecItor = vec.begin(); *vecItor != vec.end(); vecItor++)

You are using some memory, which your program probably doesn't own, as an
interator.

He owns the memory, since he new'd it.

Also, you are incrementing the pointer with vecItor++, did you
mean *vecItor++ (that is, once you actually have it pointing to some memory
set aside as an interator).

This is the problem. The code increments the pointer, not the iterator. It
should be:
++*vecItor
in the for loop.

--
Thomas
http://www.netmeister.org/news/learn2quote.html

[Victor Bazarov]

xg****@gmail.co m wrote:

On Jun 22, 6:04 pm, Andre Kostur <nntps...@kostu r.netwrote:

>"xgn...@gmail. com" <xgn...@gmail.c omwrote
innews:11***** *************** **@z28g2000prd. googlegroups.co m:

>>Suppose we have a vector:
vector<intvec (10);

>>We can declare a iterator this way:
vector<int>:: iterator vecItor;

>>and then dereference it like this:
for (vecItor = vec.begin(); vecItor != vec.end(); vecItor++)
{
cout << *vecItor << endl;
}

>>But how can we dereference the iterator if we declare it this way:
vector<int>:: iterator* vecItor;

**vecItor.

That's a pointer-to-iterator. So you need to dereference your
pointer
part, then dereference the iterator.

Thanks guys. That makes perfect sense. However, when I run this in
Visual Studio,

vector<intvec(1 0);
vector<int>::it erator* vecItor = new vector<int>::it erator();

for (*vecItor = vec.begin(); *vecItor != vec.end(); vecItor++)

... (*vecItor)++

and, REALLY, why do you need this nonsense?

{
cout << **vecItor << endl;
}

it caused debug assertion failure: vector iterators incompatible.

So I suspect there is no problem with the grammar. I just need to
search somewhere else to
find a way making VS happy.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[xgngli]

... (*vecItor)++

>
and, REALLY, why do you need this nonsense?

You are right. It should be (*vecItor)++ or ++*vecItor. I need to
declare a iterator this way because in a managed C++ class, the
compiler doesn't allow me to declare like this: vector<int>::it erator
vecItor;

Thank you for your help guys!

[Victor Bazarov]

xg****@gmail.co m wrote:

> ... (*vecItor)++

and, REALLY, why do you need this nonsense?

You are right. It should be (*vecItor)++ or ++*vecItor. I need to
declare a iterator this way because in a managed C++ class,

By "nonsense" I didn't mean a pointer to the iterator. I meant the
"managed C++".

the
compiler doesn't allow me to declare like this: vector<int>::it erator
vecItor;

Thank you for your help guys!

--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask