%%%%%%%%%%%%%%%%%%%%% Word driven tesselation  %%%%%%%%%%%%%%%%%%%
%
% CTESS
% Usage: T = DTESS(p,q,r,word,ti,drawIT,T0,e)
%
% Inputs:  p,q,r  - real numbers with 1/p +1/q +1/r < 1 
%                   see SCHWARTZ for the interpretation of p,q,r
%          word   - the sequence of reflections to drive the tesellation 
%          ti     - title of tesselation
%          drawIT - draw initial triangle
%          T0     - optional starting triangle
%          e      - optional erasure parameter, see below
%          e is a string composed of the following options
%               'B'   erase at beginning start with new boundary circle
%               'b'   do not erase at beginning 
%               'F'   clear graphics at end 
%               'f'   do not clear graphics at end  
%               default is 'BF'
%
%          the sequence of reflections given by word are used to tile the disc
%          with a p-q-r schwartz triangle

function T = ctess(p,q,r,word,ti,drawIT,T0,e)

% colour plotting options
vc1 = 'r';
vc2 = 'y';
vc3 = 'g';
cc  = 'y';
icc = 'k';
invisible = get(gcf,'Color');
verttxt =  [inttostr(p)  inttostr(q)  inttostr(r)]; 

% initializations
I = sqrt(-1);  

if (nargin >= 6)
     DIT = drawIT;
    else 
     DIT = 1;
   end; 
   
if (nargin >= 7)
     T = T0;
    else 
     T =schwartz(p,q,r);
   end; 
   
if (nargin < 8) e ='BF'; end;
erase = [sum(e == 'B') sum(e == 'F')];

if erase(1) boundary(ti,'','w'); end;
if DIT plottri(T,'w'); end;   
%plotvert(T,vc1,vc2,vc3);    % remove comment character to plot vertices in colour 
%plotvrtt(T,verttxt);        % remove comment character to plot vertex orders 

word = word(:);
n = length(word);
for i = 1:n
    side = word(i);
    T2 = trirefl(T, side);
    if (side >= 'a')&(side <= 'c')
       plottri(T2,'w');
       pause(1);
       plottri(T2,'r');
        %plotvert(T2,vc1,vc2,vc3);  % remove comment character to plot vertices in colour 
        %plotvrtt(T2,verttxt);      % remove comment character to plot vertex orders  
        end;
        T = T2;
    end;
if erase(2) clf; end;