problem with std::vector

erfi

in my header file i wrote this code:

class CMyDlg : public CDialog
{
public:
int varCount;
vector< intVec;

    // ...

}

and in the cpp file wrote this code :

void CQMDlg::OnGetvarCountButton()
{
// initialize varCount

 for(int i=0;i!=varCount;i++)    
 {
intVec.push\_back(i);
 }

}

there is no error in compilation but when i press that specific button, program hangs. can somebody help me? thanks

prasad_som

Have stepped in to the code ? what varCount is expected to initialize with? Probably its not initializing properly and going into loop.

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Waldermort

How exactly have you initialized varCount? Your loop has a problem: for(int i=0;i!=varCount;i++) while i is not equal to varCount, thats just asking for trouble. Try changing it to for(int i=0;i<varCount;i++)

erfi

thank you guys. yes, my problem was in varCount initialization. and i have another problem. when i write

intVec.

the property container menu of intVec doesn't appears.

Christian Graus

Intellisense doesn't work ? That doesn't really matter, does it ?

Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog

prasad_som

Many times, deleting .ncb file in project folder and rebuilding application do work.:)

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prasad_som

waldermort wrote:

while i is not equal to varCount, thats just asking for trouble

How?

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erfi

thanks i deleted the .ncb file and now it's working.

Mr Brainley

Because, it can easily happen, that you skip that specific value, for whatever reason. You could accidently increase the counter twice, initialize it with a value larger than varCount and stuff like that. It's just a matter of clean and readable code. If you want a loop to run as long as i is less or equal some other value, then you should write your condition that way. Lots of problems and timewasting during debugging happen due to such dirty practices. Then again, STL-Iterators work just that way ( it = YourVector.begin(); it != YourVector.end(); it++ ), but that don't mean it's good =).

prasad_som

Actually, I dont follow coding style, by OP,too. All points mentioned by you are valid. But in given code , that doesn't matter. As revealed later, it was initializatin problem.:)

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Zac Howland

prasad_som wrote:

But in given code , that doesn't matter. As revealed later, it was initializatin problem.

Actually, he probably would have caught it sooner because I'm guessing it was something like this:

void CQMDlg::OnGetvarCountButton() 
{
     varCount = -1; // just as an example
     for(int i=0; i!=varCount; ++i)    
     {
	intVec.push_back(i);
     }
}

Which will run forever, whereas if the code was written as:

void CQMDlg::OnGetvarCountButton() 
{
     varCount = -1; // just as an example
     for(int i=0; i<varCount; ++i)    
     {
	intVec.push_back(i);
     }
}

It would have been caught immediately since the vector would have been empty. As a side note, STL's iterators use != for a reason. For most of the containers, there is no guarantee that the memory locations are sequential, so you can't do a < comparison to find the end of the loop. -- modified at 10:18 Thursday 21st September, 2006

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week Zac

prasad_som

Zac Howland wrote:

for(int i=0; i!=varCount; ++i

True, I never come across such code,too.

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