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mimi
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 Posted: Wed May 16, 2007 9:10 am Post subject: Can I use iterator in this way? |
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It seems that iterator could be treated as the pointer to object. But
I am quite doubt about it.
Is using &(*iterator) instead of the pointer to object(after copy the
object from the iterator) permitted, or appreciated?
#include <vector>
int main()
{
std::vector<int> vecFoo(4, 0);
std::vector<int>::iterater iter = vecFoo.begin();
//Some function need a pointer to int, should i use
someFunc( &(*iter)); //(1)
//Should i use the following to replace the (1)
int i = *iter;
someFunc(&i);
return 0;
}
Thanks for any advice. |
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Stefan Naewe
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| Posted: Wed May 16, 2007 9:10 am Post subject: Re: Can I use iterator in this way? |
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On 5/16/2007 10:29 AM, mimi wrote:
| Quote: | It seems that iterator could be treated as the pointer to object. But
I am quite doubt about it.
Is using &(*iterator) instead of the pointer to object(after copy the
object from the iterator) permitted, or appreciated?
#include <vector
int main()
{
std::vector<int> vecFoo(4, 0);
std::vector<int>::iterater iter = vecFoo.begin();
//Some function need a pointer to int, should i use
someFunc( &(*iter)); //(1)
//Should i use the following to replace the (1)
int i = *iter;
someFunc(&i);
return 0;
}
Thanks for any advice.
|
Use:
someFunc(&vecFoo[0]);
(see: Effective STL, Item 16)
S.
--
Stefan Naewe
stefan dot naewe at atlas-elektronik dot com |
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peter koch
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| Posted: Wed May 16, 2007 9:10 am Post subject: Re: Can I use iterator in this way? |
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On 16 Maj, 10:29, mimi <cainiaodelixi...@gmail.com> wrote:
| Quote: | It seems that iterator could be treated as the pointer to object. But
I am quite doubt about it.
Is using &(*iterator) instead of the pointer to object(after copy the
object from the iterator) permitted, or appreciated?
#include <vector
int main()
{
std::vector<int> vecFoo(4, 0);
std::vector<int>::iterater iter = vecFoo.begin();
//Some function need a pointer to int, should i use
someFunc( &(*iter)); //(1)
|
This will work because your vector is not empty. If someFunc modifies
what the pointer points to, the contents of the vector will change to.
| Quote: |
//Should i use the following to replace the (1)
int i = *iter;
someFunc(&i);
return 0;
}
This will work to, but if someFunc changes what the pointer points to, |
the vector will not change. So it comes down to what effect you're
trying to achieve.
/Peter |
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Ivan Vecerina
Guest
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| Posted: Wed May 16, 2007 9:11 am Post subject: Re: Can I use iterator in this way? |
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"mimi" <cainiaodelixiang (AT) gmail (DOT) com> wrote in message
news:1179304180.251436.257130 (AT) k79g2000hse (DOT) googlegroups.com...
: It seems that iterator could be treated as the pointer to object. But
: I am quite doubt about it.
: Is using &(*iterator) instead of the pointer to object(after copy the
: object from the iterator) permitted, or appreciated?
:
: #include <vector>
:
: int main()
: {
: std::vector<int> vecFoo(4, 0);
: std::vector<int>::iterater iter = vecFoo.begin();
:
: //Some function need a pointer to int, should i use
: someFunc( &(*iter)); //(1)
This will work for (almost*) all iterators for accessing (only)
the item pointed to by the iterator.
In the case of a vector<>::iterator *only*, you can even index
the resulting pointer to access adjacent items (within the
bounds of the vector). E.g. someFunc( (&*iter)+1 ) will
be the same as &vecFoo[1].
* Some exceptions and caveats:
- istream_iterator: the * operator will return a temporary
object. While it will be possible to access its address,
the temporary object will only be valid until the
completion of the statement.
- An item class could overload the address-of operator (&)
in and unexpected way, but this would probably cause other
failures anyway.
: //Should i use the following to replace the (1)
: int i = *iter;
: someFunc(&i);
Making a copy of the item is unnecessary in this case.
I hope this helps,
Ivan
--
http://ivan.vecerina.com/contact/?subject=NG_POST <- email contact form
Brainbench MVP for C++ <> http://www.brainbench.com |
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mimi
Guest
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| Posted: Wed May 16, 2007 9:11 am Post subject: Re: Can I use iterator in this way? |
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On 5月16日, 下午4时37分, Stefan Naewe <nos...@please.net> wrote:
| Quote: | On 5/16/2007 10:29 AM, mimi wrote:
It seems that iterator could be treated as the pointer to object. But
I am quite doubt about it.
Is using &(*iterator) instead of the pointer to object(after copy the
object from the iterator) permitted, or appreciated?
#include <vector
int main()
{
std::vector<int> vecFoo(4, 0);
std::vector<int>::iterater iter = vecFoo.begin();
//Some function need a pointer to int, should i use
someFunc( &(*iter)); //(1)
//Should i use the following to replace the (1)
int i = *iter;
someFunc(&i);
return 0;
}
Thanks for any advice.
Use:
someFunc(&vecFoo[0]);
(see: Effective STL, Item 16)
Thank you very much. I have the impression of the Item but i don't |
remember which item. Thanks a lot for reminding me that.
| Quote: | S.
--
Stefan Naewe
stefan dot naewe at atlas-elektronik dot com- 隐藏被引用文字 -
- 显示引用的文字 - |
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