Vector Iterator problem in VS2005

May 29, 2009 at 4:43 AM

Hi I got some strange problem. I have code in visual c++ 6. and i upgrade it to VS 2005 compiler . Since this days STL changed lot of things i am getting some assert error. Here my code look like this. // look for v1 vector::iterator result = find(face.begin(),face.end(),v1); vector::iterator prev = result - 1; // <=== this point i am getting assert error. Can anyone tell me why it gives me error ? [Edited by - nareshn2008 on May 29, 2009 5:04:39 AM]

May 29, 2009 at 4:56 AM

Maybe because std::find returns face.begin(). Then face.begin() - 1 is invalid.

Codeka

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Codeka

May 29, 2009 at 5:01 AM

I don't see how that would compile, a vector::iterator cannot be converted to a vector::iterator (unless BSP_VertexInd is a typedef for int, but that would be confusing)

Author

May 29, 2009 at 5:05 AM

Quote:
Original post by Codeka
I don't see how that would compile, a vector::iterator cannot be converted to a vector::iterator (unless BSP_VertexInd is a typedef for int, but that would be confusing)

Sorry i was miss it. I just want to show simple example :)

124

May 29, 2009 at 5:08 AM

Quote:
Original post by Codeka
I don't see how that would compile, a vector::iterator cannot be converted to a vector::iterator (unless BSP_VertexInd is a typedef for int, but that would be confusing)

#include <vector>struct BSP_VertexInd {};namespace std {        template <> struct vector<BSP_VertexInd> {                struct iterator {                        template <typename T> iterator (T const &) {}                };        };}using std::vector;vector<int>::iterator result;vector<BSP_VertexInd>::iterator prev = result - 1; // <=== this point i am getting assert error.int main () {}

Compiles fine, no typedef harmed ;)

124

May 29, 2009 at 5:14 AM

Quote:
Original post by nareshn2008
Quote:
Original post by Codeka
I don't see how that would compile, a vector::iterator cannot be converted to a vector::iterator (unless BSP_VertexInd is a typedef for int, but that would be confusing)

Sorry i was miss it. I just want to show simple example :)

We will be able to help you if you post a real, preferably minimal, testcase :)

Author

May 29, 2009 at 7:01 AM

Quote:
Original post by phresnel
Quote:
Original post by nareshn2008
Quote:
Original post by Codeka
I don't see how that would compile, a vector::iterator cannot be converted to a vector::iterator (unless BSP_VertexInd is a typedef for int, but that would be confusing)

Sorry i was miss it. I just want to show simple example :)

We will be able to help you if you post a real, preferably minimal, testcase :)

Hi phresnel

Thanks for reply :)

This is real code.

vector::iterator result =
find(face.m_verts.begin(),face.m_verts.end(),v1);

vector::iterator prev = result - 1; // << here is error

BSP_VertexInd is some sort of structure .

May 29, 2009 at 7:15 AM

Quote:
Original post by nareshn2008
Quote:
Original post by phresnel
Quote:
Original post by nareshn2008
Quote:
Original post by Codeka
I don't see how that would compile, a vector::iterator cannot be converted to a vector::iterator (unless BSP_VertexInd is a typedef for int, but that would be confusing)

Sorry i was miss it. I just want to show simple example :)

We will be able to help you if you post a real, preferably minimal, testcase :)

Hi phresnel

Thanks for reply :)

This is real code.

vector::iterator result =
find(face.m_verts.begin(),face.m_verts.end(),v1);

vector::iterator prev = result - 1; // << here is error

BSP_VertexInd is some sort of structure .

Did you check what std::find returns?

Author

May 29, 2009 at 7:24 AM

Hi

It is returns face.begin(). So what will be trick to reverse_iterator ?

May 29, 2009 at 7:37 AM

Quote:
Original post by nareshn2008
Hi

It is returns face.begin(). So what will be trick to reverse_iterator ?

But what do you expect? You can't get an element before the first one. That's an error.

Author

May 29, 2009 at 7:50 AM

Hi

I must tell you i am not expecting anything :)

I just got this code from library and i am using it. In VC6 it working fine. in VC2005 this error. Because of more changes in STL. in VC6 iterator act like pointer.

So i am expecting to see how can i figure out this code.

SiS-Shadowman

May 29, 2009 at 7:54 AM

Well, you have a pointer that points to the first element of the array. If you decrement that pointer by another element, you're out of bounds. There is no element before the first one. If you want the last, then use face.end() - 1, but that is only valid when there is at least one item in it. Just because "it runs" doesn't mean that it is valid code.

*edit* So if you aren't expecting anything, why'd you copy the code in the first place?

124

May 29, 2009 at 8:01 AM

Quote:
Original post by rozz666
Quote:
Original post by nareshn2008
Hi

It is returns face.begin(). So what will be trick to reverse_iterator ?

But what do you expect? You can't get an element before the first one. That's an error.

Though that would be a runtime error, not a compile time error like claimed in the OP.

May 29, 2009 at 8:53 AM

Quote:
Original post by phresnel
Quote:
Original post by rozz666
Quote:
Original post by nareshn2008
Hi

It is returns face.begin(). So what will be trick to reverse_iterator ?

But what do you expect? You can't get an element before the first one. That's an error.

Though that would be a runtime error, not a compile time error like claimed in the OP.

It is a runtime error.

Quote:
Original post by nareshn2008
...am getting some assert error.

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