function theResult = demonstrate(varargin)

% demonstrate -- Evaluate and display a command.
%  demonstrate ... or demonstrate('...') evaluates
%   the concatenated argument(s) as a single command
%   and returns or displays a single string showing
%   the answer adjacent to the command itself.
%  demonstrate (no argument) shows help and
%   demonstrates several commands.
 
% Copyright (C) 1998 Dr. Charles R. Denham, ZYDECO.
%  All Rights Reserved.
%   Disclosure without explicit written consent from the
%    copyright owner does not constitute publication.
 
% Version of 14-Aug-1998 09:12:02.

if nargin < 1 & nargout < 1
	help(mfilename)
	demonstrate datestr(now)
	demonstrate sqrt(2)
	demonstrate min(2, 3)
	demonstrate 2 * 3
	oldWarning = warning;
	warning off
	demonstrate [-1 0 1] / 0
	warning(oldWarning)
	return
end

theCommand = '';
for i = 1:length(varargin)
	if i > 1, theCommand = [theCommand ' ']; end
	theCommand = [theCommand varargin{i}];
end

okay = 1;
theAnswer = [];
lasterr('')
theAnswer = evalin('caller', theCommand, '[]');
if ~isempty(lasterr), theAnswer = ['Error: ' lasterr]; end

result = [theCommand ' ==> ' mat2str(theAnswer)];

if nargout > 0
	theResult = result;
else
	disp([' ' result])
end