function r8_ei_test ( )

%*****************************************************************************80
%
%% R8_EI_TEST tests R8_EI.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    23 April 2016
%
%  Author:
%
%    John Burkardt
%
  addpath ( '../test_values' );

  fprintf ( 1, '\n' );
  fprintf ( 1, 'R8_EI_TEST:\n' );
  fprintf ( 1, '  R8_EI evaluates the exponential integral Ei(X).\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '             X           EI(X)  R8_EI(X)        Diff\n' );
  fprintf ( 1, '\n' );

  n_data = 0;

  while ( 1 )

    [ n_data, x, fx1 ] = ei_values ( n_data );

    if ( n_data == 0 )
      break
    end

    fx2 = r8_ei ( x );

    fprintf ( 1, '  %14.4f  %14.6g  %14.6g  %14.6g\n', x, fx1, fx2, abs ( fx1 - fx2 ) );

  end

  rmpath ( '../test_values' );

  return
end
