/* shuffle.c - in-place shuffling (bit-reversal) of a complex array */#include <cmplx.h>void swap();int bitrev();void shuffle(N, X)complex *X;int N;                                    /* \(N\) must be a power of 2 */{       int n, r, B=1;       while ( (N >> B) > 0 )             /* \(B\) = number of bits */              B++;       B--;                               /* \(N = 2\sp{B}\) */       for (n = 0; n < N; n++) {           r = bitrev(n, B);              /* bit-reversed version of \(n\) */           if (r < n) continue;           /* swap only half of the \(n\)s */           swap(X+n, X+r);                /* swap by addresses */           }}