Ok--- So, I guess this goes along with my confusion about arrays and pointers...
I have this code:
@implementation Autocorrelator
+(float *)coefficientsFor:(Buffer *)buffer {
float coefficients[11];
for (int i = 0; i <= 10; i++) {
coefficients[i] = [self aForLag:i buffer:buffer];
}
return coefficients;
}
+(float)aForLag:(NSUInteger)lag buffer:(Buffer *)buffer {
NSUInteger samples = [buffer size] - lag;
float sum = 0.0f;
for (int i = 0; i < samples; i++) {
sum += buffer.samples[i] * buffer.samples[i + lag];
}
return sum;
}
...
which I would like to call like this:
-(void)something {
float *coefficients = [Autocorrelator coefficientsFor:self.buffer];
// do something with the coefficients array
}
However, I am getting a compiler warning saying that coefficientsFor: is
returning a stack memory address associated with a local variable, which makes
sense...
but if I change
float coefficients[11];
to:
float *coefficients;
That warning goes away, but I don't understand why that would be acceptable..
How does it know the size of the array? Does it not matter?
The other way I can imagine doing this would be:
+(void)coefficientsFor:(Buffer *)buffer coefficients:(float *)coefficients {
for (int i = 0; i <= 10; i++) {
coefficients[i] = [self aForLag:i buffer:buffer];
}
}
and have my caller do:
-(void)something {
float coefficients[11];
[Autocorrelator coefficientsFor:buffer coefficients:coefficients];
// do something with coefficients array;
}
...
Am I on the right track? Are these my only options?
Patrick J. Collins
http://collinatorstudios.com
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