you have to also define it in the h file of ofApp, ie:
class ofApp : public ofSimpleApp{
.....
float distance(int n,int valX, int valY);
....
}
you have to also define it in the h file of ofApp, ie:
class ofApp : public ofSimpleApp{
.....
float distance(int n,int valX, int valY);
....
}