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

%*****************************************************************************80
%
%% arccos_values() returns some values of the arc cosine function.
%
%  Discussion:
%
%    In Mathematica, the function can be evaluated by:
%
%      ArcCos[x]
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    12 June 2007
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Milton Abramowitz, Irene Stegun,
%    Handbook of Mathematical Functions,
%    National Bureau of Standards, 1964,
%    ISBN: 0-486-61272-4,
%    LC: QA47.A34.
%
%    Stephen Wolfram,
%    The Mathematica Book,
%    Fourth Edition,
%    Cambridge University Press, 1999,
%    ISBN: 0-521-64314-7,
%    LC: QA76.95.W65.
%
%  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 = 12;

  fx_vec = [ ...
    1.6709637479564564156, ...
    1.5707963267948966192, ...
    1.4706289056333368229, ...
    1.3694384060045658278, ...
    1.2661036727794991113, ...
    1.1592794807274085998, ...
    1.0471975511965977462, ...
    0.92729521800161223243, ...
    0.79539883018414355549, ...
    0.64350110879328438680, ...
    0.45102681179626243254, ...
    0.00000000000000000000 ];

  x_vec = [ ...
    -0.1, ...
     0.0, ...
     0.1, ...
     0.2, ...
     0.3, ...
     0.4, ...
     0.5, ...
     0.6, ...
     0.7, ...
     0.8, ...
     0.9, ...
     1.0 ];

  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
