As a final test, let's use faust2octave to obtain the four overlaid Bode plots in Fig.1, but now for the discrete-time system. Our test program is as follows:
g=0.1; // wcT or 2*sin(wcT/2) [see exact digital poles] y = ( + : ( + <: (*(g):+~_),_)~*(0-sqrt(2)) : (_ <: (*(g):+~_),_),_)~*(-1); yl = y : _', ! , ! ; // lowpass (delay usually not needed) yb = y : ! , _' , ! ; // bandpass (delay usually not needed) yh = y : ! , ! , _; // highpass yn = yl + yh; // notch (delay compensation required here) process = 1-1' <: yl,yb,yh,yn; // impulse-response test for faust2octaveRunning faust2octave on this followed by semilogx(w,db(abs(fft(faustout,8192)(1:4097,:)))) produces the plot overlays shown in Fig.7.