#include <stdio.h>
     #include <math.h>
     #include <gsl/gsl_randist.h>
     
     int
     main (void)
     {
       double x;
       const gsl_rng_type * T;
       gsl_rng * r;
       
       gsl_rng_env_setup ();
       
       T = gsl_rng_default;
       r = gsl_rng_alloc (T);
     
       for (x = 0.1; x < 2; x+= 0.1)
         {
           double y0 = exp (x);
           double sigma = 0.1 * y0;
           double dy = gsl_ran_gaussian (r, sigma);
     
           printf ("%g %g %g\n", x, y0 + dy, sigma);
         }
     
       gsl_rng_free(r);
     
       return 0;
     }