You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: calln.m
    path of file: ./repos/d2d/arFramework3/ThirdParty/StrucID/adimat/scalar_directderivs
    
    the code of the file until where you have to start completion: function res= calln(func, varargin)
%CALLN Call func with all arguments are gradients.
%
% calln(@f, g_v1, g_v2,..., g_vn) expects all g_vi to be directional 
% derivatives, violation of this rule results in incorrect results or errors.
%

    
function res= calln(func, varargin)
%CALLN Call func with all arguments are gradients.
%
% calln(@f, g_v1, g_v2,..., g_vn) expects all g_vi to be directional 
% derivatives, violation of this rule results in incorrect results or errors.
%
% Copyright 2008 Andre Vehreschild, Institute for Scientific Computing
%                     RWTH Aachen University
% This code is under development! Use at your own risk! Duplication,
% modification and distribution FORBIDDEN!

% Ensure, that func is a function handle and not a string.
if ~ isa(func, 'function_handle')
   func= str2fun(func);
end