#define N 1024    /* Length of output buffers */
#define L N       /* Length of input data     */
#define logL 10   /* log base 2 of L          */
#define M 31      /* Compute 2*M+1 autocorrelation points */

/* #define M (L/2-1) */ /* Be sure to use ()'s in this case */
                        /* or algebraic substitution bugs   */ 
                        /* can be introduced                */