% set parameters to default values
    [PARA] = set_defaults;

        FUN.name        = 'fgamma';     % name of approximant
        BASIS.name      = 'monom';      % name of basis function
        BASIS.choice    = [0:3];        % this is the special choice
        BASIS.C_dim     = length(BASIS.choice);
        BOUNDARY.name   = 'gcircle';    % name of boundary
        critical_points = []';
        C_dim           = BASIS.C_dim;
        real_coef       = 1;

        PARA.relative_error_bound = 1e-15;
        PARA.max_iterations       = 200;
        PARA.output               = 'none';       
        PARA.plot                 = 'end: abserror+boundary'; 
        
        PARA.as_subroutine = 1;

    % addparameter specific parameters 
    PARA = set_defaults(PARA,FUN,BASIS,BOUNDARY,...
                        critical_points,real_coef,C_dim);

    % call the COCA package
    % http://www.math.mu-luebeck.de/workers/modersitzki/COCA/coca5.html
    [PARA] = coca(PARA);

    % do some output
    disp([PARA.lower_bound,PARA.error_norm])