Figure 3: Partial listing of file filter_types.h, structs for specifying specific filter types and their frequency responses in constructing an FIR filter
struct Low_pass { double Fc; // Cutoff frequency double Fs; // Sampling frequency int N; // number of non-repeated coefficients // Constructor Low_pass (double fc, double fs, int n) : Fc(fc), Fs(fs), N(n) {} }; // structs High_pass and Band_pass not shown here