"An Access Violation error"

[im1crazyloser]

Ok, so i have read about it on the web before posting this and i have changed it time and time and it still does not work. I am using Dev-C++ (as my instructor insisted) and it complies correctly but does not run. Here is the part of my code that does not work:

int main(){

float plotPoints [20][20];

float value = 0.0;

for ( int y = 0; y <= 20; y++ ){
for ( int x = 0; x <= 20; x++ ){

x = x - 10;
y = y - 10;

value = ( sqrt( pow( x, 2.0 ) + pow( y, 2.0 ) ) + 0.001 );

plotPoints [x][y] = ( (sin(value)) / value ); // THE ERROR OCCURS HERE
}
}

for ( int y = 0; y <= 20; y++ ){
for ( int x = 0; x <= 20; x++ ){
cout << plotPoints [x][y];
}
}

return 0;
}

i know it is a issue with the pointer and memory, i just dont understand how to fix it.

Thanks

[turbozedd]

Use the code wrapper please.

You cannot address negative array values. If you need to use your indices for calculation, do not overwrite them!

for ( int y = 0; y <= 20; y++ ){
  for ( int x = 0; x <= 20; x++ ){
    value = ( sqrt( pow( x-10, 2.0 ) + pow( y-10, 2.0 ) ) + 0.001 );

...
  }
}

[im1crazyloser]

It works now.
Thank you so much turbozedd.

[eker676]

Btw for future reference:

x = x -10
can be shortened using the shortcut operator -=
x -= 10

This works for +,-,*,/, and %

[kempofighter]

Even if the problem with accessing arrays with negative values didn't exist in the program, which turbo pointed out you'd still have a continuous for loop with no chance of exit. The x variable used for the for loop is initialized to 0, and immediately changed to -10. If the program didn't crash, how would the loop ever exit?

[seymore15074]

And if x and y are not manipulated within the body of the for loop, the indices would attempt to access beyond the boundaries of plotPoints.