例如ones函数的源代码：看不太懂，求助！

Question

function [varargout] = ones(varargin)
%ONES Ones array.
% ONES(N) is an N-by-N matrix of ones.
%
% ONES(M,N) or ONES([M,N]) is an M-by-N matrix of ones.
%
% ONES(M,N,P,...) or ONES([M N P ...]) is an M-by-N-by-P-by-... array of
% ones.
%
% ONES(SIZE(A)) is the same size as A and all ones.
%
% ONES with no arguments is the scalar 1.
%
% ONES(M,N,...,CLASSNAME) or ONES([M,N,...],CLASSNAME) is an M-by-N-by-...
% array of ones of class CLASSNAME.
%
% Example:
% x = ones(2,3,'int8');
%
% See also EYE, ZEROS.

% Copyright 1984-2003 The MathWorks, Inc.
% $Revision: 5.10.4.3 $ $Date: 2004/04/16 22:05:14 $
% Built-in function.

if nargout == 0
builtin('ones', varargin{:});
else
[varargout{1:nargout}] = builtin('ones', varargin{:});
end

Answer 1

if nargout == 0 % nargout代表函数实际输出参数的个数。% 如果在命令行直接调用ones(...)，nargout=0% 如果给一个变量赋值，比如a=ones(...)，nargout=1% 如果给若干变量赋值，如[a, b, ...]=ones(...)，有几个变量，nargout就是几。builtin('ones', varargin{:}); % 如果无输出参数，调用内建的ones函数else[varargout{1:nargout}] = builtin('ones', varargin{:}); % 否则，同样调用内建ones函数，但要给输出变量赋值返回的结果。varargout表示所有输出参数组成的队列。end