An error in QwtScaleDiv::invert

[alex_sh]

Hello,

I noticed an error in QwtScaleDiv::invert() (VS /analyze caught it) :

for ( int i = 0; i < NTickTypes; i++ )
    {
        QList<double>& ticks = d_ticks[i];
 
        const int size = ticks.count();
        const int size2 = size / 2;
 
        for ( int i = 0; i < size2; i++ )
            qSwap( ticks[i], ticks[size - 1 - i] );
    }

for ( int i = 0; i < NTickTypes; i++ )
    {
        QList<double>& ticks = d_ticks[i];

        const int size = ticks.count();
        const int size2 = size / 2;

        for ( int i = 0; i < size2; i++ )
            qSwap( ticks[i], ticks[size - 1 - i] );
    }

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I believe the second for() should use j or something instead of i.

Thanks!

[ars]

It's not a bug (assuming that the inner loop really should use a new loop variable). The inner for loop uses a new instance of variable i. Check the output of the following small program:

#include <iostream>
using namespace std;
 
int main(int , char**)
{
	for (int i=0; i < 5; i++)
	{
		cout << i << " ";
		for(int i=0; i < 3; i++)
			if(i == 0)
				cout << i << endl;
			else
				cout << "  " << i << endl;
	}
}

#include <iostream>
using namespace std;

int main(int , char**)
{
	for (int i=0; i < 5; i++)
	{
		cout << i << " ";
		for(int i=0; i < 3; i++)
			if(i == 0)
				cout << i << endl;
			else
				cout << "  " << i << endl;
	}
}

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But I would also prefer a new name for the inner for loop variable just for code readability.

[alex_sh]

Yes, you're right, I missed that.
Too much late-night debugging with suspicious tools, I guess...

[Stig]

Uwe,

Regarding your commit; just pointing out that you don't increment the j variable in the inner loop:

for ( int j = 0; j < size2; i++ )
qSwap( ticks[j], ticks[size - 1 - j] );