/* dac.c - bipolar two's complement D/A converter */double dac(b, B, R)int *b, B;                         /* bits are dimensioned as \(b[0], b[1], \dotsc, b[B-1]\) */double R;{       int i;       double dac = 0;       b[0] = 1 - b[0];                          /* complement MSB */       for (i = B-1; i >= 0; i--)                /* H\"orner's rule */          dac = 0.5 * (dac + b[i]);       dac = R * (dac - 0.5);                    /* shift and scale */       b[0] = 1 - b[0];                          /* restore MSB */       return dac;}