function f = p31_f ( x )

%*****************************************************************************80
%
%% p31_f() evaluates the objective function for test 31.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    23 February 2026
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    real x: the argument.
%
%  Output:
%
%    real f: the function value.
%
  f = 1.2 + sin ( 2.5 * sqrt ( abs ( x ) + x ) );

  return
end
