push_back not saving order?

[daviddoria]

I have some code like this:

vector<double> Saved;
for(int i = 0; i<10; i++)
{
  if(some condition on i)
      Saved.push_back(i);
}

Then I want to see what order the things were saved... so naturally I do

cout << Saved.at(0) << endl << Saved.at(1) << endl;

But to my surprise they aren't in the right order!! Pretty odd if you ask me...

I would expect the first thing output there to always be less than the second thing... correct??

The actual code follows, but relies on a bunch of stuff so I don't think it will be very helpful:

for(int scancounter = 0; scancounter < NumScans; scancounter++) //alpha loop

	{

		for(int concentriccol = 0; concentriccol < ColsPerScan; concentriccol++) //beta loop

		{
			B.clear();
			V1.clear();
			V2.clear();

			B = LiDARGrid.ConcentricScans.at(scancounter).getColumn(concentriccol);	

		
			double Penalty = CreateComparableVectors(A,B,V1,V2);


			double distance = VectorDistance(V1,V2) + Penalty;


			if(distance < 100) //distance bigger than this is unreliable

			{
				if(distance <= BestDistance)

				{

					BestDistance = distance;

					BestScanPositions.push_back(scancounter);

					BestCols.push_back(concentriccol);

				}
			}
			

		}//end col loop

	}//end scanner loop

	cout << "Input Scan: " << CorrectPosition << " Col: " << CorrectCol << endl

			<< "Matching Scans: " << endl
			<< BestScanPositions.at(0) << " Col: " << BestCols.at(0) << endl
			<< BestScanPositions.at(1) << " Col: " << BestCols.at(1) << endl
			<< "Best Distance: " << BestDistance << endl
			<< "There were " << BestScanPositions.size() << " good matches." << endl << endl;

An example is BestScanPositions.at(0) is 0 and BestScanPositions.at(1) is also 0. Then BestCols.at(0) is 19 and BestCols.at(1) is 16!!! Weird, eh?

Please let me know if I'm doing something wrong..

Thanks,

Dave

[Ancient Dragon]

1) when using vectors you can access individual elelements just as you would do with a simple int array B = LiDARGrid.ConcentricScans.[scancounter].getColumn(concentriccol); Otherwise, this works. Your problem is probably something other than push_back

#include <vector>
#include <iostream>
using namespace std;

int main()
{
vector<double> Saved;
for(int i = 0; i<10; i++)
{
    if( (i%2) == 0)
        Saved.push_back(i);
}
vector<double>::iterator it;
for(it = Saved.begin(); it != Saved.end(); it++)
{
    cout << *it << "\n";
       
}


}

[bugmenot]

1) when using vectors you can access individual elelements just as you would do with a simple int array B = LiDARGrid.ConcentricScans.[scancounter].getColumn(concentriccol);

except that it doesn't check bounds

[Ancient Dragon]

except that it doesn't check bounds

at() and [] both throw exceptions on out-of-bounds, at least it does with VC++ 2008 Express.

[edit]Nope, I'm wrong. Adding try/catch block the at() will throw and exception, but [] will just simply crash. But this is not relevent if the coder doesn't use try/catch blocks.[/edit]

[mitrmkar]

An example is BestScanPositions.at(0) is 0 and BestScanPositions.at(1) is also 0. Then BestCols.at(0) is 19 and BestCols.at(1) is 16!!! Weird, eh?

Just guessing .. could it be that you actually do the 'offending' loop twice or more without clearing the vectors' content in between?