function [ n_data, x, fx ] = bessel_j0_spherical_values ( n_data )

%*****************************************************************************80
%
%% bessel_j0_spherical_values() returns some values of the Spherical Bessel function j0.
%
%  Discussion:
%
%    In Mathematica, the function can be evaluated by:
%
%      Sqrt[Pi/(2*x)] * BesselJ[1/2,x]
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    23 August 2004
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Milton Abramowitz and Irene Stegun,
%    Handbook of Mathematical Functions,
%    US Department of Commerce, 1964.
%
%    Stephen Wolfram,
%    The Mathematica Book,
%    Fourth Edition,
%    Wolfram Media / Cambridge University Press, 1999.
%
%  Input:
%
%    integer N_DATA.  The user sets N_DATA to 0 before the first call.  
%    Thereafter, it should simply be the value returned by the previous call.
%
%  Output:
%
%    integer N_DATA.  On each call, the routine increments N_DATA by 1, and
%    returns the corresponding data; when there is no more data, the
%    output value of N_DATA will be 0 again.
%
%    real X, the argument of the function.
%
%    real FX, the value of the function.
%
  n_max = 21;

  fx_vec = [ ...
      0.9983341664682815E+00, ...
      0.9933466539753061E+00, ...
      0.9735458557716262E+00, ...
      0.9410707889917256E+00, ...
      0.8966951136244035E+00, ...
      0.8414709848078965E+00, ...
      0.7766992383060220E+00, ...
      0.7038926642774716E+00, ...
      0.6247335019009407E+00, ...
      0.5410264615989973E+00, ...
      0.4546487134128408E+00, ...
      0.3674983653725410E+00, ...
      0.2814429918963129E+00, ...
      0.1982697583928709E+00, ...
      0.1196386250556803E+00, ...
      0.4704000268662241E-01, ...
     -0.1824191982111872E-01, ...
     -0.7515914765495039E-01, ...
     -0.1229223453596812E+00, ...
     -0.1610152344586103E+00, ...
     -0.1892006238269821E+00 ];

  x_vec = [ ...
     0.1E+00, ...
     0.2E+00, ...
     0.4E+00, ...
     0.6E+00, ...
     0.8E+00, ...
     1.0E+00, ...
     1.2E+00, ...
     1.4E+00, ...
     1.6E+00, ...
     1.8E+00, ...
     2.0E+00, ...
     2.2E+00, ...
     2.4E+00, ...
     2.6E+00, ...
     2.8E+00, ...
     3.0E+00, ...
     3.2E+00, ...
     3.4E+00, ...
     3.6E+00, ...
     3.8E+00, ...
     4.0E+00 ];

  if ( n_data < 0 )
    n_data = 0;
  end

  n_data = n_data + 1;

  if ( n_max < n_data )
    n_data = 0;
    x = 0.0;
    fx = 0.0;
  else
    x = x_vec(n_data);
    fx = fx_vec(n_data);
  end

  return
end
