% Plot murray polygon
% Based on Jack Cole's original S-Algol program
% http://alb.host.cs.st-andrews.ac.uk/cole/code.html

clf

% Radices for polygon
rx=[3 3 3];
ry=[3 3 3];

% Set up radices, state and rectangle size
x_rad = length(rx); 
y_rad = length(ry); 
max_rad = max(x_rad, y_rad);
complexity = 2 * max_rad;
digits = zeros(complexity + 1,1);
radices = ones(complexity + 1,1);
parities = ones(complexity + 1,1);
k=1;
for i = 1:2:(2 * x_rad)
    radices( i ) = rx(k); k=k+1;
end
k=1;
for i = 2:2:(2 * y_rad)
    radices( i ) = ry(k); k=k+1;
end

no_pts = number_pts( radices,1,1 ) -1
nx = number_pts( radices,1,2 )
ny = number_pts( radices,2,2 )
width = max(nx,ny);
x1 = 0;
y1 = 0;
x2 = 0;
y2 = 0;

% Drawing variables
mx=0; % Maximum extent
my=0;
im=zeros(nx,ny); % For drawing color picture
coords=[x1 y1]; % Save states as coordinate array

for ii = 1:no_pts
    [digits,i] = increment( digits,radices,1 ) ;
    parities = change_parities( parities,i ) ;
    inc = parities( i + 1 )*2-1;
    if rem(i,2) == 1
        x2 = x2 + inc;
    else
        y2 = y2 + inc;
    end
    
    % Display
    %plot([x1 x2],[y1 y2],'LineWidth',2); hold on; drawnow
    % plot([x1 x2],[y1 y2],'Color',.5+.5*[cos(3*ii/no_pts) cos(3*ii/no_pts+1) cos(3*ii/no_pts+2)]); hold on
    im(x2+1,y2+1)=ii;
    coords=[coords; x2 y2];
    
    if rem(i,2) == 1
        x1 = x2;
    else
        y1 = y2;
    end
    mx=max(mx,x1);
    my=max(my,y1);
end

clf
plot(coords(:,1),coords(:,2),'-','LineWidth',2);
axis([-1 mx+1 -1 my+1]);
axis equal
axis off