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

%*****************************************************************************80
%
%% dawson_values() returns some values of Dawson's integral.
%
%  Discussion:
%
%    The definition of Dawson's integral is
%
%      D(X) = exp ( -X * X ) * Integral ( 0 <= Y <= X ) exp ( Y * Y ) dY
%
%    Dawson's integral has a maximum at roughly
%
%      X = 0.9241388730
%
%    In Mathematica, the function can be evaluated by:
%
%      Sqrt[Pi] * Exp[-x^2] * I * Erf[I*x] / 2
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    16 September 2004
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Milton Abramowitz and Irene Stegun,
%    Handbook of Mathematical Functions,
%    US Department of Commerce, 1964.
%
%    Eric Weisstein,
%    CRC Concise Encyclopedia of Mathematics,
%    CRC Press, 1998.
%
%    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 = [ ...
     0.0000000000000000E+00, ...
     0.9933599239785286E-01, ...
     0.1947510333680280E+00, ...
     0.2826316650213119E+00, ...
     0.3599434819348881E+00, ...
     0.4244363835020223E+00, ...
     0.4747632036629779E+00, ...
     0.5105040575592318E+00, ...
     0.5321017070563654E+00, ...
     0.5407243187262987E+00, ...
     0.5380795069127684E+00, ...
     0.5262066799705525E+00, ...
     0.5072734964077396E+00, ...
     0.4833975173848241E+00, ...
     0.4565072375268973E+00, ...
     0.4282490710853986E+00, ...
     0.3999398943230814E+00, ...
     0.3725593489740788E+00, ...
     0.3467727691148722E+00, ...
     0.3229743193228178E+00, ...
     0.3013403889237920E+00 ];

  x_vec = [ ...
     0.0E+00, ...
     0.1E+00, ...
     0.2E+00, ...
     0.3E+00, ...
     0.4E+00, ...
     0.5E+00, ...
     0.6E+00, ...
     0.7E+00, ...
     0.8E+00, ...
     0.9E+00, ...
     1.0E+00, ...
     1.1E+00, ...
     1.2E+00, ...
     1.3E+00, ...
     1.4E+00, ...
     1.5E+00, ...
     1.6E+00, ...
     1.7E+00, ...
     1.8E+00, ...
     1.9E+00, ...
     2.0E+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
