“Variable Array set but not used”

manpreet Best Answer 2 years ago

I am trying to set up and use an array in c++. The array has been declared and been used, but I keep getting back the error "variable set but not used", even though I have used it in the program.

It works on Linux but not Windows 10.

#include 
#include 
using namespace std;

int main()
{
    int sampling_rate = 44100;
    double dt = 1.0 / sampling_rate;
    int duration = 1;
    int number_of_samples = duration / dt;
    int sample_array[number_of_samples];
    int amplitude = 5000;

    cout << "sampeling rate = " << sampling_rate<<endl;

    for (int sample_number = 0; sample_number < sampling_rate; sample_number++)
    {
      double sample_time = sample_number * dt;
      sample_array[sample_number] = amplitude * sin(2 * M_PI * 293 * sample_time);
    }
}

I expect this code to make an array that can then be converted to a sine wave.

manpreet 2 years ago

Your compiler’s warning points out (correctly) that you only ever write to your array, you never read the results.

Since you’re not reading the results, why compute them in the first place? Your compiler is entirely correct in noting that this is useless work, and assumes that you probably forgot to actually, you know, use the computed values.

As this is only a warning and not an error you can ignore it for now if this code is work in progress. In “finished” code you should however be very alarmed by such a warning since it almost certainly points to a bug in your code.