function value = rosenbrock ( xy )

%*****************************************************************************80
%
%% rosenbrock evaluates the rosenbrock function.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    03 October 2019
%
%  Input:
%
%    real xy(2): the x and y arguments.
%
%  Output:
%
%    real value: the function value.
%
  x = xy(1);
  y = xy(2);

  value = 100.0 * ( y - x.^2 ).^2 + ( 1.0 - x ).^2;

  return
end

