Lyapunov

/* A Copy of the C example of the Lyapunov exponent taken from C.A.Pickovers Chaos In Wonderland... */

Lsum = 0;
n = 0;
x = 0.1;
y = 0.1;
xe = x + 0.000001;
ye = y;

REPEAT 10,000,000 TIMES
       xx = sin(y*b) + c*sin(x*b) ;
       yy = sin(x*a) + d*sin(y*a) ;
       xsave = xx;
       ysave = yy;
       x = xe;
       y = ye;
       n++;

/* "Re-Iterate" for computing Lyapunov Exponent, L */
   xx = sin(y*b) + c*sin(x*b) ;
   yy = sin(x*a) + d*sin(y*a) ;
   dLx = xx - xsave;
   dLy = yy - ysave;
   dL2 = dLx*dLx + dLy*dLy;
   df = 1000000000000.*dL2;
   rs = 1./sqrt(df);
   xe = xsave + rs*(xx - xsave);
   ye = ysave + rs*(yy - ysave);
   xx = xsave;
   yy = ysave;
   Lsum = Lsum + log(df);
   L = 0.721347*Lsum/n;
   x = xx;
   y = yy;
/* L is the value for the Lyapunov exponent */
END REPEAT