function [ n_data, x, fx ] = struve_l1_values ( n_data )

%*****************************************************************************80
%
%% struve_l1_values() returns some values of the Struve L1 function.
%
%  Discussion:
%
%    In Mathematica, the function can be evaluated by:
%
%      StruveL[1,x]
%
%    The data was reported by McLeod.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    19 September 2004
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Milton Abramowitz and Irene Stegun,
%    Handbook of Mathematical Functions,
%    US Department of Commerce, 1964.
%
%    Allan McLeod,
%    Algorithm 757, MISCFUN: A software package to compute uncommon
%      special functions,
%    ACM Transactions on Mathematical Software,
%    Volume 22, Number 3, September 1996, pages 288-301.
%
%    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 = 20;

  fx_vec = [ ...
     0.80950410749865126939E-06, ...
     0.20724649092571514607E-03, ...
     0.33191834066894516744E-02, ...
     0.53942182623522663292E-01, ...
     0.22676438105580863683E+00, ...
     0.11027597873677158176E+01, ...
     0.91692778117386847344E+01, ...
     0.15541656652426660966E+03, ...
     0.26703582852084829694E+04, ...
     0.86505880175304633906E+06, ...
     0.11026046613094942620E+07, ...
     0.22846209494153934787E+07, ...
     0.42454972750111979449E+08, ...
     0.48869614587997695539E+09, ...
     0.56578651292431051863E+10, ...
     0.76853203893832108948E+12, ...
     0.14707396163259352103E+17, ...
     0.29030785901035567967E+21, ...
     0.58447515883904682813E+25, ...
     0.11929750788892311875E+30 ];

  x_vec = [ ...
       0.0019531250E+00, ...
      -0.0312500000E+00, ...
       0.1250000000E+00, ...
      -0.5000000000E+00, ...
       1.0000000000E+00, ...
       2.0000000000E+00, ...
      -4.0000000000E+00, ...
       7.0000000000E+00, ...
     -10.0000000000E+00, ...
      16.0000000000E+00, ...
      16.2500000000E+00, ...
     -17.0000000000E+00, ...
      20.0000000000E+00, ...
      22.5000000000E+00, ...
     -25.0000000000E+00, ...
      30.0000000000E+00, ...
     -40.0000000000E+00, ...
      50.0000000000E+00, ...
      60.0000000000E+00, ...
     -70.0000000000E+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
