Experiments with Matlab by Cleve Moler_rabbit.m file
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Hi all,
I downloaded all the example matlab files in Moler's excellent book, "Experiments with Matlab". When I ran the rabbit.m file, I got the following error:
??? Error: File: rabbits.m Line: 150 Column: 25 Unexpected MATLAB operator.
Code reproduced below.
function rabbits(handle)
% RABBITS Fibonacci's rabbit pen.
% How fast does the population grow?
% rabbits, with no arguments, initializes the simulation.
% rabbits(handle) is the callback with each button click.
% Initialize with a blue bunny in the center of the figure.
% Clicking on a blue bunny turns it into a blue rabbit.
% Clicking on a blue rabbit creates a gray bunny and turns the rabbit gray.
% Clicking on a gray bunny or gray rabbit does nothing.
% When all the bunnies and rabbits are gray, count them and turn them all blue.
% R = structure of rabbit images.
% pos = history of positions.
persistent R pos
if nargin == 0
% Initialize single blue bunny and uicontrols.
init_graphics
else
% Process a button click.
switch get(handle,'tag')
case 'bluebunny'
% A blue bunny turns into a gray rabbit.
bluebunny(handle)
case 'bluerabbit'
% A blue rabbit creates a gray bunny and turns gray itself.
bluerabbit(handle)
case 'graybunny'
% A gray bunny does nothing.
case 'grayrabbit'
% A gray rabbit does nothing.
end
% When all are gray, turn them all blue.
update
end
% ------------------------------
function init_graphics
clf reset
shg
R = load('rabbits.mat');
R.graybunny = cat(3,R.bunny,R.bunny,R.bunny);
R.grayrabbit = cat(3,R.rabbit,R.rabbit,R.rabbit);
R.bluebunny = cat(3,R.bunny,R.bunny,255*ones(size(R.bunny),'uint8'));
R.bluerabbit = cat(3,R.rabbit,R.rabbit,255*ones(size(R.rabbit),'uint8'));
f = get(gcf,'position');
p = .45*f(3:4);
pos = p;
% Single bunny
uicontrol('style','pushbutton','position',[p 80 80], ...
'background','white','cdata',R.bluebunny,'tag','bluebunny', ...
'callback','rabbits(gcbo)');
% Population counter
uicontrol('style','text','fontsize',12,'fontweight','bold', ...
'position',[f(3)/2-14 f(4)-40 28 28],'string','1')
% Auto toggle
uicontrol('style','toggle','position',[20 20 60 20], ...
'string','auto','callback',@auto)
end
% ------------------------------
function bluebunny(handle)
% A blue bunny turns into a gray rabbit.
set(handle,'cdata',R.grayrabbit,'tag','grayrabbit', ...
'callback','rabbits(gcbo)')
end
% ------------------------------
function bluerabbit(handle)
% A blue rabbit creates a gray bunny and turns gray itself.
p = find_good_position;
uicontrol('style','pushbutton','position',[p 80 80], ...
'background','white','cdata',R.graybunny,'tag','graybunny', ...
'callback','rabbits(gcbo)');
set(handle,'cdata',R.grayrabbit,'tag','grayrabbit', ...
'callback','rabbits(gcbo)');
end
% ------------------------------
function p = find_good_position
% Avoid toggle and population counter.
f = get(gcf,'position');
ds = -Inf;
% Choose best of several random positions.
for k = 1:20
p = .80*f(3:4).*rand(1,2);
% Avoid toggle in lower right hand corner.
if p(1) < 80 && p(2) < 40
continue
end
% Avoid population counter centered near the top.
f = get(gcf,'pos');
if (p(2)+80 > f(4)-40) && (p(1)+80 > f(3)/2-14) ...
&& (p(1) < f(3)/2+14)
continue
end
r = p(ones(size(pos,1),1),:);
d = min(min(abs(pos-r)'));
if d > ds
ds = d;
ps = p;
end
end
p = ps;
pos = [pos; p];
end
% ------------------------------
function update
% When all are gray, turn them all blue.
b = findobj(gcf,'style','pushbutton');
n = length(b);
c = get(b,'tag');
if n == 1
c = {c};
end
% Check for all gray.
if length(findstr([c{:}],'gray')) == n
pause(1.0)
for k = 1:n
if findstr(c{k},'graybunny')
set(b(k),'cdata',R.bluebunny,'tag','bluebunny', ...
'callback','rabbits(gcbo)')
else
set(b(k),'cdata',R.bluerabbit,'tag','bluerabbit', ...
'callback','rabbits(gcbo)');
end
end
% Update population counter.
set(findobj(gcf,'style','text'),'string',n)
end
end
% ------------------------------
function auto(handle,~)
% Auto toggle callback
% Complete one month's growth
set(handle,'enable','off')
b = [findobj(gcf,'tag','bluebunny')
findobj(gcf,'tag','bluerabbit')];
n = length(b);
b = b(randperm(n));
for k = 1:n
rabbits(b(k))
pause(.1)
end
set(handle,'enable','on','value',0)
end
end % rabbits
回答（5 个）
Walter Roberson
2011-12-18
0 个投票
Change the ~ to any otherwise-unused variable name.
Fangjun Jiang
2011-12-18
0 个投票
You probably worked on a MATLAB version earlier than R2009b, which does not support the new feature regarding the use of ~ symbol for unused input or output arguments.
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