function y = test_fun ( x )

%*****************************************************************************80
%
%% test_fun() evaluates a function used for demonstrations.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    23 February 2026
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    real x(): the evaluation points.
%
%  Output:
%
%    real y(): the function values.
%
  y = x.^4 + 10.0 * x .* sin ( x.^2 );

  return
end
