function value = f3 ( x )

%*****************************************************************************80
%
%% f3() evaluates trigonometric interpolation test function #3.
%
%  Discussion:
%
%    F3 is periodic but nondifferentiable at an interior point.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    28 August 2019
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    real x, the evaluation points.
%
%  Output:
%
%    real value, the function value at x.
%
  value = ( 3.0 * x <= 1.0 ) .* 3.0 .* x ...
        + ( 1.0 <= 3.0 * x ) .* 1.5 .* ( 1.0 - x ); 

  return
end

