iterator problem

[Chameleon]

All these happen in VC++ NET 2003, if you ask me about the compiler.
it._Myptr is a VC++ specific member of the iterator implementation.
But from this, we extract usefull informations about crash.
----------------------------
vector<int*> v;
vector<int*>::i terator it = v.begin(); // it._Myptr == 0 (what pointer
is this?)
v.insert(it, 5); // works
it++; // it._Myptr == 4
v.insert(it, 5); // crashes
----------------------------
and this.
----------------------------
vector<int*> v;
vector<int*>::i terator it = v.begin(); // it._Myptr == 0
v.push_back(5);
vector<int*>::i terator it = v.begin(); // it._Myptr == 0x00323b40 (the
pointer to first element)
----------------------------


All of these are compiler bugs on iterator implementation, or I miss
something?

Thanks

[Calum Grant]

Re: iterator problem

Chameleon wrote:[color=blue]
> All these happen in VC++ NET 2003, if you ask me about the compiler.
> it._Myptr is a VC++ specific member of the iterator implementation.
> But from this, we extract usefull informations about crash.
> ----------------------------
> vector<int*> v;
> vector<int*>::i terator it = v.begin(); // it._Myptr == 0 (what
> pointer is this?)[/color]

The same as v.end(). No bug. You're not going to dereference it.
[color=blue]
> v.insert(it, 5); // works[/color]

That's okay, but invalidates "it".
[color=blue]
> it++; // it._Myptr == 4[/color]

Unfortunately, "it" is invalid.
[color=blue]
> v.insert(it, 5); // crashes[/color]

Yup.
[color=blue]
> ----------------------------
> and this.
> ----------------------------
> vector<int*> v;
> vector<int*>::i terator it = v.begin(); // it._Myptr == 0
> v.push_back(5);[/color]

This compiles?
[color=blue]
> vector<int*>::i terator it = v.begin(); // it._Myptr == 0x00323b40
> (the pointer to first element)
> ----------------------------
>
>
> All of these are compiler bugs on iterator implementation, or I miss
> something?[/color]

Ah, not every error is a compiler error!

Cheers, Calum

[Daniel T.]

Re: iterator problem

In article <ds38pl$jpi$1@v olcano1.grnet.g r>,
Chameleon <cham_gss@hotma il.NOSPAM.com> wrote:
[color=blue]
> All of these are compiler bugs on iterator implementation, or I miss
> something?[/color]

Until you know enough that you can build your own compiler, go ahead and
assume that the bug is in your code rather than the compiler's code...
Just a thought.


--
Magic depends on tradition and belief. It does not welcome observation,
nor does it profit by experiment. On the other hand, science is based
on experience; it is open to correction by observation and experiment.

[Chameleon]

Re: iterator problem

Calum Grant wrote:[color=blue]
> Chameleon wrote:[color=green]
>> All these happen in VC++ NET 2003, if you ask me about the compiler.
>> it._Myptr is a VC++ specific member of the iterator implementation.
>> But from this, we extract usefull informations about crash.
>> ----------------------------
>> vector<int*> v;
>> vector<int*>::i terator it = v.begin(); // it._Myptr == 0 (what
>> pointer is this?)[/color]
>
> The same as v.end(). No bug. You're not going to dereference it.
>[color=green]
>> v.insert(it, 5); // works[/color]
>
> That's okay, but invalidates "it".
>[color=green]
>> it++; // it._Myptr == 4[/color]
>
> Unfortunately, "it" is invalid.
>[color=green]
>> v.insert(it, 5); // crashes[/color]
>
> Yup.
>[color=green]
>> ----------------------------
>> and this.
>> ----------------------------
>> vector<int*> v;
>> vector<int*>::i terator it = v.begin(); // it._Myptr == 0
>> v.push_back(5);[/color]
>
> This compiles?[/color]

sorry, vector<int> v;
[color=blue][color=green]
>> vector<int*>::i terator it = v.begin(); // it._Myptr == 0x00323b40
>> (the pointer to first element)
>> ----------------------------
>>
>>
>> All of these are compiler bugs on iterator implementation, or I miss
>> something?[/color]
>
> Ah, not every error is a compiler error![/color]


of-course!

my solution is this until now:

-------------------------------------
vector<int*> v;
vector<int*>::i terator it = v.begin();
it = v.insert(it, 5);
it++;
it = v.insert(it, 5);
-------------------------------------

[Luke Meyers]

Re: iterator problem

Chameleon wrote:[color=blue][color=green][color=darkred]
> >> vector<int*> v;
> >> vector<int*>::i terator it = v.begin(); // it._Myptr == 0
> >> v.push_back(5);[/color]
> >
> > This compiles?[/color]
>
> sorry, vector<int> v;[/color]

Okay, vector<int>. Good.
[color=blue]
> my solution is this until now:
>
> -------------------------------------
> vector<int*> v;
> vector<int*>::i terator it = v.begin();
> it = v.insert(it, 5);
> it++;
> it = v.insert(it, 5);
> -------------------------------------[/color]

Back to vector<int*> now? Well, in any case... line 2 above serves no
purpose. I would change this snippet to:

std::vector<int > v;
v.push_back(5);
v.push_back(5);

See? No need for iterators at all in this case. Maybe you got
confused because you didn't know about push_back? You owe it to
yourself to learn the public interface of important classes like
std::vector. It is only wafer-thin.

Luke