function [z1, z2] = addsub (x, y)   % only one returned variable
%     function z = addsub (x, y)          % Alternative function form
% ----------------------------------------------------------------------
% Usage: [sum, difference] = addsub (x, y)   (Note the comma or blank space.)
% Usage: [sum  difference] = addsub (x, y)
%
% This function adds and substracts two numbers/matrices given in the argument
% Demonstrate how to pass and output multiple arguments.
%   Calling Example #1: a=addsub(1,2)     ...  gives a=3
%   Calling Example #2: [a b]=addsub(1,2) ...  gives a=3 & b=-1
%-----------------------------------------------------------------------
% Instructor: Nam Sun Wang
%-----------------------------------------------------------------------

% The first blank line above signifies the end point for help.
% More comments go here, but this line will not be displayed when you issue
% "help" from MATLAB.

      z1 = x + y;
      z2 = x - y;
% An example to check for the number of arguments in the output in the calling
% statement so that if the calling line has only one output (as in Calling
% Example #1), there is no sense calculating the second variable.
%     if (nargout==2) z2 = x - y; end

% The following is for the alternative function form
%     z = [z1 z2];

% No "end" or "end function" statement is needed as each function must be
% compleletely contained in a separate .M file.