#include <stdio.h>

#include <gsl/gsl_math.h>

#include <gsl/gsl_chebyshev.h>

double

f (double x, void *p)

{

  (void)(p); /* avoid unused parameter warning */

  if (x < 0.5)

    return 0.25;

  else

    return 0.75;

}

int

main (void)

{

  int i, n = 10000; 

  gsl_cheb_series *cs = gsl_cheb_alloc (40);

  gsl_function F;

  F.function = f;

  F.params = 0;

  gsl_cheb_init (cs, &F, 0.0, 1.0);

  for (i = 0; i < n; i++)

    {

      double x = i / (double)n;

      double r10 = gsl_cheb_eval_n (cs, 10, x);

      double r40 = gsl_cheb_eval (cs, x);

      printf ("%g %g %g %g\n", 

              x, GSL_FN_EVAL (&F, x), r10, r40);

    }

  gsl_cheb_free (cs);

  return 0;

}