function [] = boxe7
% boxe7: animated trace of exercise E7 --
%        user must type a key to advance from one movie frame to the next

if nargin < 1
    n = 3;
end

if n>3
    warning('boxfib does not work well for n>3')
end

f.act_ = 'draw activation record';
f.header_ = strvcat(' ', 'function [x,y] = f(a,b)');
fcode = strvcat(...
'% draw pic!', ...
'x = b-a;       ', ...
'y = a;         ', ...
'% draw pic!');
fcode = [repmat(' ',size(fcode,1),4) fcode];

g.act_ = f.act_;
g.header_ = strvcat(' ', 'function x = g(a,b)');
gcode = strvcat(...
'% draw pic!', ... % 1
'a = 2*a;       ', ... % 2
'b = 2*b;       ', ... % 3
'               ', ... % 4
'[a,b] = f(b,a);', ... % 5
'a = 2*a;       ', ... % 6
'b = 3*b;       ', ... % 7
'x = a-b;       ', ... % 8
'% draw pic!');
gcode = [repmat(' ',size(gcode,1),4) gcode];

ccode = strvcat(...
'a = 10;        ', ... % 1
'b = 20;        ', ... % 2
'x = 30;        ', ... % 3
'% draw pic!', ... % 4
'               ', ... % 5
'x = g(15, 6);  ', ... % 6
'% draw pic!');
ccode = [repmat(' ',size(ccode,1),4) ccode];


big.command.code_ = ccode; boxdisp(big);

big.command.a = 10; 
ccode(:, 1:4) = ' '; ccode(1, 1:3) = '-->';
big.command.code_ = ccode;  boxdisp(big);

big.command.b = 20; 
ccode(:, 1:4) = ' '; ccode(2, 1:3) = '-->';
big.command.code_ = ccode;  boxdisp(big);

big.command.x = 30; 
ccode(:, 1:4) = ' '; ccode(3, 1:3) = '-->';
big.command.code_ = ccode;  boxdisp(big);

ccode(:, 1:4) = ' '; ccode(4, 1:3) = '-->';
big.command.code_ = ccode;  boxdisp(big);

ccode(:, 1:4) = ' '; ccode(5, 1:3) = '-->';
ccode(5, 9:16) = '?';
big.command.code_ = ccode;  boxdisp(big);

% > call to g --------------------------------------------------

g.code_ = gcode;
big.g = g; boxdisp(big);

g.act_ = strvcat('draw parameters;', 'fill with arguments');
g.a = 15; g.b = 6;
big.g = g; boxdisp(big);

g.act_ = 'run function body';
g.code_ = gcode; g.code_(1,1:3) = '-->';
big.g = g; boxdisp(big);

g.a = 2*g.a;
g.code_ = gcode; g.code_(2,1:3) = '-->';
big.g = g; boxdisp(big);

g.b = 2*g.b;
g.code_ = gcode; g.code_(3,1:3) = '-->';
big.g = g; boxdisp(big);

g.code_ = gcode; g.code_(4,1:3) = '-->';
g.code_(4, 13:18) = '?';
big.g = g; boxdisp(big);

% > call to g > call to f --------------------------------------

f.code_ = fcode;
big.f = f; boxdisp(big);

f.act_ = strvcat('draw parameters;', 'fill with arguments');
f.a = g.b; f.b = g.a;
big.f = f; boxdisp(big);

f.act_ = 'run function body';
f.code_ = fcode; f.code_(1,1:3) = '-->';
big.f = f; boxdisp(big);

f.x = f.b - f.a;
f.code_ = fcode; f.code_(2,1:3) = '-->';
big.f = f; boxdisp(big);

f.y = f.a;
f.code_ = fcode; f.code_(3,1:3) = '-->';
big.f = f; boxdisp(big);

f.code_ = fcode; f.code_(4,1:3) = '-->';
big.f = f; boxdisp(big);

f.code_ = [];
f.act_ = strvcat('copy out return values;', 'kill activation record');
f = rmfield(f,['a' ; 'b']);
s = sprintf('[%d, %d]', f.x, f.y);
g.code_(4, :) = ' '; g.code_(4, 12+(1:length(s))) = s;
g.code_(4, 1:3) = '-->';
big.g = g;
big.f = f; boxdisp(big);

big = rmfield(big, 'f'); boxdisp(big);
% > call to g < call to f --------------------------------------

g.a = f.x; g.b = f.y;
g.code_ = gcode; g.code_(5,1:3) = '-->';
g.code_(4, 12+(1:length(s))) = s;
big.g = g; boxdisp(big);

g.a = 2*g.a;
g.code_ = gcode; g.code_(6,1:3) = '-->';
big.g = g; boxdisp(big);

g.b = 3*g.b;
g.code_ = gcode; g.code_(7,1:3) = '-->';
big.g = g; boxdisp(big);

g.x = g.a - g.b;
g.code_ = gcode; g.code_(8,1:3) = '-->';
big.g = g; boxdisp(big);

g.code_ = gcode; g.code_(9,1:3) = '-->';
big.g = g; boxdisp(big);

g.code_ = [];
g.act_ = strvcat('copy out return value;', 'kill activation record');
g = rmfield(g,['a' ; 'b']);
s = num2str(g.x);
ccode(:, 1:4) = ' ';
ccode(5, :) = ' '; ccode(5, 8+(1:length(s))) = s;
ccode(5, 1:3) = '-->';
big.g = g; big.command.code_ = ccode; boxdisp(big);

big = rmfield(big, 'g'); boxdisp(big);
% < call to g --------------------------------------------------

big.command.x = g.x;
ccode(:, 1:4) = ' '; ccode(6, 1:3) = '-->';
big.command.code_ = ccode;  boxdisp(big);

ccode(5,:) = ' ';
ccode(:, 1:4) = ' '; ccode(7, 1:3) = '-->';
big.command.code_ = ccode;  boxdisp(big);

function [] = boxdisp(big)
    s = boxscope(big,1); % pre-compute to avoid delay between $clc$ and $disp$
    clc; disp(s); pause