/* dtftr.c - N DTFT values over frequency range [wa, wb) */#include <cmplx.h>                                 /* complex arithmetic */complex dtft();                                    /* DTFT at one frequency */void dtftr(L, x, N, X, wa, wb)                     /* usage: dtftr(L, x, N, X, wa, wb); */double *x, wa, wb;                                 /* \(x\) is \(L\)-dimensional real */complex *X;                                        /* \(X\) is \(N\)-dimensional complex */int L, N;{       int k;       double dw = (wb-wa)/N;                      /* frequency bin width */       for (k=0; k<N; k++)              X[k] = dtft(L, x, wa + k*dw);        /* \(k\)th DTFT value \(X(\om\sb{k})\) */}