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: betacdf.m
    path of file: ./repos/fieldtrip/external/stats
    
    the code of the file until where you have to start completion: % Copyright (C) 2012 Rik Wehbring
% Copyright (C) 1995-2012 Kurt Hornik
%
% This file is part of Octave.
%
% Octave is free software; you can redistribute it and/or modify it
% under the terms of 
    
function
% (CDF) at @var{x} of the Beta distribution with parameters @var{a} and
% @var{b}.
% @end deftypefn

% Author: KH <Kurt.Hornik@wu-wien.ac.at>
% Description: CDF of the Beta distribution

function cdf = betacdf (x, a, b)

  if (nargin ~= 3)
    print_usage ();
  end