function [] = lec220(in, skip)
% lec220. animation of execution of max-of-sequence example in 2/20 lecture
% usage: lec220() or lec220(inputValues) or lec220(inputValues, skip)
% $inputValues$: the vector of input values, excluding the terminating 0
% $skip$:
% 0 (default value): animate each step
% 1 : animate only loop iterations (skip loop body)
% inf : generate html/png output
% lec220([5 -3 8 17 5 19 18], inf)
if nargin == 0
in = [5 -3 8 17 5 19 18];
end
if nargin <= 1
skip = 0;
end
if any(in == 0)
error('input sequence contains 0')
end
invcolor = 'g'; % color of invariant when true
notinvcolor = 'r'; % color of invariant when false
yescolor = 'c'; % color of activated if/while when guard is true
nocolor = 'm'; % color of activated if/while when guard is false
oncolor = 'b'; % color of other activated line of code
in = [in(:)' 0];
step = [];
step = [step -1];
i = 0;
i = i+1; num = in(i);
curmax = -inf;
stopping = 0;
% inv %0
step = [step 1];
while num ~= stopping %1
step = [step 2];
if num > curmax %2
step = [step 3];
curmax = num; %3
CURMAX{length(step)} = curmax;
step = [step 4];
end %4
step = [step 5];
i = i+1; num = in(i); %5
I{length(step)} = i;
step = [step 6 1];
end %6
step = [step 7];
% after %7
CURMAX{length(step)+1} = [];
I{length(step)+1} = [];
tests = [1 2]; % lines with tests
program = strvcat(...
'num = input(prompt); curmax = -inf;', ...
'% inv: curmax = maxsofar(excluding num)', ...
'while num ~= stopping', ...
' if num > curmax;', ...
' curmax = num;', ...
' end', ...
' num = input(prompt);', ...
'end', ...
'... code after while loop...');
figure(1);
set(1,'Position',[10 300 870 384]);
clf
hold on
axis([-2 9 0 14]);
axis ij
axis off
adj = 2;
for line = -1:7
h(line+adj) = mytext(1, adj+line, program(line+adj,:));
end
h(0+adj) = myplot([.8 .8 8 8 .8], [2.5 1.5 1.5 2.5 2.5], invcolor);
set(mytext(0, 12, 'input:'), 'HorizontalAlignment','right');
for i = 1:length(in)
hin(i) = mytext(i, 12, sprintf('%d', in(i)));
end
set(hin,'HorizontalAlignment','center')
harrow = myplot([0 .75], [0+adj 0+adj], 'k->');
hnum = mytext(1, 11, 'num');
set(hnum, 'HorizontalAlignment','center');
hnuml = myplot([.5 1.5], [11.5 11.5], 'y');
hmax = mytext(0.5, 11, 'maxsofar = -oo');
set(hmax, 'HorizontalAlignment','right');
hmaxl = myplot([0 .5], [11.5 11.5], 'b');
hcur = mytext(0.5, 13, 'curmax = -oo');
set(hcur, 'HorizontalAlignment','right');
hcurl = myplot([0 .5], [12.5 12.5], 'b');
num = in(1); curmax = -inf; maxsofar = -inf;
ii = 1;
if isinf(skip)
for i = 1:length(step)
prev = find(step==1); prev = max(prev(prev < i));
next = find(step==1); next = min(next(next > i));
fid = fopen(sprintf('%02d.htm',i),'w');
fprintf(fid, '\n');
fprintf(fid, 'Step %02d\n', i);
fprintf(fid, '\n');
fprintf(fid, '
\n', i);
fprintf(fid, '
', i);
fprintf(fid, '| program: | %s%s
|---|
\n', aref('start',min(1,i-1)), aref('end',max(39,i+1)));
fprintf(fid, '| loop iteration: | %s%s
|---|
\n', aref('prev',prev), aref('next',next));
fprintf(fid, '| line of code: | %s%s
|---|
\n', aref('prev',i-1), aref('next',i+1));
fprintf(fid, '
\n');
fprintf(fid, '\n');
fprintf(fid, '\n');
fclose(fid);
end
end
for i = 1:length(step)
s = step(i);
color = oncolor;
if ismember(s,tests)
if s+1 == step(i+1)
color = yescolor;
else
color = nocolor;
end
end
set(h(s+adj), 'Color', color);
set(harrow,'YData', [s+adj s+adj]);
if ~isempty(I{i})
ii = I{i};
num = in(ii);
before = in(1:ii-1);
[maxsofar,where] = max(before);
set(hmax, 'Position', [where 11 0]);
set(hmax, 'HorizontalAlignment','center');
set(hmax, 'String', 'maxsofar');
set(hmaxl, 'XData', [0 ii-.5]);
set(hnum, 'Position', [ii 11 0]);
set(hnuml, 'XData', ii + [-.5 .5]);
end
if s == 3 | (s == 2 & (step(i+1) ~= 3))
[curmax,where] = max(in(1:ii));
set(hcur, 'Position', [where 13 0]);
set(hcur, 'HorizontalAlignment','center');
set(hcur, 'String', 'curmax');
set(hcurl, 'XData', [0 ii+.5]);
end
color = notinvcolor;
if maxsofar == curmax, color = invcolor; end;
set(h(0+adj),'Color',color);
set(hmax,'Color',color);
set(hcur,'Color',color);
if (s == 1 & ~isinf(skip)) | ~skip, pause; end
if isinf(skip)
f = getframe;
fname = num2str(1000+i);
fname = [fname(end-1:end) '.png'];
imwrite(f.cdata,f.colormap,fname);
end
set(h(s+adj), 'Color', 'k');
end
function h = mytext(x,y,t)
h = text(x,y,t);
set(h, 'FontSize',16, 'FontName','Courier');
function h = myplot(x,y,s)
h = plot(x,y,s);
set(h, 'LineWidth', 4);
function location = aref(label,i)
location = ['(' label ') | '];
if isempty(i)
elseif i<1 | i>39
else location = sprintf('%s | ',i, label);
end