function findeigenvalues(funcName,tol)

% FINDEIGENVALUES This function will set up a Graphical Object 
%        which can be used to find the eigenvalues of some
%        specified Schrodinger equation.  It does this by
%        a binary search method, and the user must supply
%        an upper and lower bound for the calculation. 
%        The call to this function is:
%               findeigenvalues(funcName,tol)
%        tol : tolerance for the calculation (default 0.0001)
%        funcName : the name of the function (a string) which
%        calculates the getjunction at x=0 between two halves of 
%        the wave function.  Both variables are optional. 
%        This package could be used to find a zero of any 
%        function of one variable, but it is designed to be 
%        used in the Introduction to Quantum Theory 
%        course.  Therefore if it is not explicitly passed,
%        the variable funcName is assumed to be: 'getjunction'.
%        At the end, the value E, for which: 'funcName'(E) = 0,  
%        will appear on the screen, and will be stored in an
%        array called 'spectrum' in the command workspace.

%--------------------------------------------------------------------
%         Open the GUI environment
%--------------------------------------------------------------------

% Make sure the object containing all the global variables is open.

setglobals('Hidden');

set(0,'ShowHiddenHandles','on');

%--------------------------------------------------------------------
%         Test the entry information is in order
%--------------------------------------------------------------------

global psi;   % To share results with function 'funcName'

% Set up default variables if they weren't explicitly passed.
if nargin==0,
   funcName = 'getjunction';
end;

% The variable funcName is used on different entry modes. 
switch funcName
   case {'DoTheHunt','ShowYmax','ShowYmin',...
	     'ClearDisplay','ExportResult','Exit'}
      action = funcName;
otherwise
	  action = 'Initialize';
	  if nargin<2,
	     tol = 0.0001;
      end;   
end;

% ------------------------------------------------------------------
%         INITIALIZE THE GRAPHICAL USER INTERFACE
% ------------------------------------------------------------------

if strcmp(action,'Initialize')

   % ---------------------------------------------------
   %     Reopen the finder object or make a new one
   % ---------------------------------------------------

   tealColor  = [0.0,0.57,0.50];
   lightColor = [0.0 0.73 0.60];

   h_figs = get(0,'children');
   Hf_hunt = findobj(h_figs,'flat','tag',funcName);
   % Note: the finder is tagged with the funcName.
   % If it's not there the figure will have to be initialized.
   
   if length(Hf_hunt)==0
      Hf_hunt = figure('color',tealColor,...
                       'units','normalized', ...
                       'position',[0.36 0.70 0.60 0.23],...
                       'Name','Eigenvalue finder',...
					   'HandleVisibility','off',...
				       'Tag',funcName,...
				       'NumberTitle','off');
				 
      % ------------------------------------------------
	  % Set up objects on first GUI input frame
	  % All the handles are saved in the variable "handles"

      % The upper frame
      hndl_dummy = uicontrol(Hf_hunt,...
	                        'style','frame',...
                            'backgroundcolor',tealColor,...
                            'units','normalized',...
		    				'position',[0.03 0.50 0.80 0.45]);
      % The label for xMax 
      hndl_dummy = uicontrol(Hf_hunt,...
	                        'style','text',...
                            'backgroundcolor',tealColor, ...
                            'units','normalized',...
    						'position',[0.05 0.75 0.30 0.15],...
                            'string','Enter an upper bound');
      % The input for xMax
      handles.xmax = uicontrol(Hf_hunt,...
	                        'Style','edit',...
                            'units','normalized',...
   					        'position',[0.37 0.75 0.20 0.15]);
      % The button for yMax
      handles.bmax = uicontrol(Hf_hunt,...
	                        'Style','pushbutton',...
                            'backgroundcolor',tealColor,...
                            'units','normalized',...
   						    'position',[0.30 0.55 0.28 0.15],...
                            'string','Calculate the function:');
      % The value of yMax
      handles.ymax = uicontrol(Hf_hunt,...
	                        'Style','text',...
                            'backgroundcolor',lightColor,...
                            'units','normalized',...
   				            'position',[0.60 0.55 0.20 0.15]);
 
      % ------------------------------------------------
	  % Set up objects on second GUI input frame

      % The lower frame
      hndl_dummy = uicontrol(Hf_hunt,...
	                        'style','frame',...
                            'backgroundcolor',tealColor,...
                            'units','normalized',...
				    		'position',[0.03 0.00 0.80 0.45]);
      % The label for xMin
      hndl_dummy = uicontrol(Hf_hunt,...
	                        'style','text',...
	                        'backgroundcolor',tealColor, ...
	                        'units','normalized',...
						    'position',[0.05 0.25 0.30 0.15],...
	                        'string','Enter an lower bound');
      % The input for xMin
	  handles.xmin = uicontrol(Hf_hunt,...
	                        'Style','edit',...
	                        'units','normalized',...
						    'position',[0.37 0.25 0.20 0.15]);
	  % The button for yMin
	  handles.bmin = uicontrol(Hf_hunt,...
	                        'Style','pushbutton',...
	                        'backgroundcolor',tealColor,...
	                        'units','normalized',...
						    'position',[0.30 0.05 0.28 0.15],...
	                        'string','Calculate the function:');
	  % The value of yMin
	  handles.ymin= uicontrol(Hf_hunt,...
	                        'Style','text',...
	                        'backgroundcolor',lightColor,...
	                        'units','normalized',...
						    'position',[0.60 0.05 0.20 0.15]);

      % ------------------------------------------------
	  % Set up objects on right hand GUI input frame

	  % The right frame
	  hndl_dummy = uicontrol(Hf_hunt,...
	                         'style','frame',...
	                         'backgroundcolor',tealColor,...
                             'units','normalized',...
							 'position',[0.86 0.00 0.14 0.95]);
	  % The button to hunt
	  handles.bhunt = uicontrol(Hf_hunt,...
	                         'Style','pushbutton',...
	                         'backgroundcolor',tealColor,...
	                         'units','normalized',...
					         'position',[0.88 0.71 0.10 0.18],...
	                         'string','Hunt');
							 
	  % The button to Export the solution
	  handles.bexpt = uicontrol(Hf_hunt,...
	                         'Style','pushbutton',...
	                         'backgroundcolor',tealColor,...
	                         'units','normalized',...
    				         'position',[0.88 0.49 0.10 0.18],...
	                         'string','Export');
	
	  % The button to clear the display
	  handles.bclr = uicontrol(Hf_hunt,...
	                         'Style','pushbutton',...
	                         'backgroundcolor',tealColor,...
	                         'units','normalized',...
						     'position',[0.88 0.27 0.10 0.18],...
	                         'string','Clear');
	
	  % The button to escape
	  handles.besc = uicontrol(Hf_hunt,...
	                         'Style','pushbutton',...
	                         'backgroundcolor',tealColor,...
	                         'units','normalized',...
 						     'position',[0.88 0.05 0.10 0.18],...
	                         'string','Close');
				 
      % ------------------------------------------------
	  % Re-open the wave solution graph, or open a new one
	  	  
	  handles.grph = OpenSolutionGraph;
	  
	  % This is in the SUBSIDIARY FUNCTION section
	  % If the solution is to be plotted, the handle to its
	  % figure will be stored as the 16th handle. 
							 
      % ------------------------------------------------	  
      % Store other handles and passed variables for use in callBacks

      handles.tol = tol;
	  % NOTE: The variable 'tol' is stored as the 17th handle.
	  %       The name of the function is stored in the 'tag' 
	  %       of the figure. It can't be stored in 'userdata'.  
      handles.E = 0;
	  %       The final result of the search is stored as
	  %       the 18th handle so it can be displayed later.
	  set(Hf_hunt,'userdata',handles);

      % ------------------------------------------------
	  % Set up the callBack events for data entry buttons

	  inputMaxCall = ...
	         ['findeigenvalues(''ShowYmax'');'];
		
      set(handles.xmax,'callBack',inputMaxCall);
	  set(handles.bmax,'callBack',inputMaxCall);
		
	  inputMinCall = ...
	         ['findeigenvalues(''ShowYmin'');'];
		
      set(handles.xmin,'callBack',inputMinCall);
	  set(handles.bmin,'callBack',inputMinCall);
		

      % ------------------------------------------------
	  % Set up the callBack events for control buttons

 	   huntCall = ...
	         ['findeigenvalues(''DoTheHunt'');'];
	   set(handles.bhunt,'callBack',huntCall);
	   
 	   ExportCall = ...
	         ['findeigenvalues(''ExportResult'');'];
	   set(handles.bexpt,'callBack',ExportCall);
	
	   clearCall = ...
	         ['findeigenvalues(''ClearDisplay'');'];
	   set(handles.bclr,'callBack',clearCall);
	   
	   closeCall = ...
	        ['set(0,''ShowHiddenHandles'',''on'');'...
			 'close;'...
			 'set(0,''ShowHiddenHandles'',''off'');'];
	   set(handles.besc, 'callBack',closeCall);
	   
      % ------------------------------------------------

   else   % if length(Hf_hunt)~=0, tolerance might have changed
      Hf_hunt = gcf;
      handles = get(gcf,'userdata');
	  if nargin>1 
	     handles.tol = tol;
		 set(gcf,'userdata',handles);
	  end;
   end; 
   
   figure(Hf_hunt);

end; % if strcmp(action,'initialize')

% ------------------------------------------------------------------
%         PART 2: HUNT FOR THE ZERO
% ------------------------------------------------------------------

if strcmp(action,'DoTheHunt')

   Hf_hunt  = gcf;
   handles  = get(gcf,'userdata');
   tol      = handles.tol;	  
   funcName = get(gcf,'tag');
   OpenSolutionGraph;
   
   % ---------------------------------------------------
   %        Check appropriate bounds are entered
   % ---------------------------------------------------

   OKtoProceed = 1;
   xMaxStr = get(handles.xmax,'string');
   xMinStr = get(handles.xmin,'string');
   if (isempty(xMaxStr))|(isempty(xMinStr)),
      warndlg('Both bounds have not been entered.');
      OKtoProceed = 0;
   else
      xMax = str2num(get(handles.xmax,'string'));
      yMax = str2num(get(handles.ymax,'string'));
	  xMin = str2num(get(handles.xmin,'string'));
      yMin = str2num(get(handles.ymin,'string'));
      if yMax*yMin>0,
         warndlg('Both endpoints have the same sign.');
         OKtoProceed = 0;
      end;
   end;

   % ---------------------------------------------------
   %        Narrow the bounds by binary chop
   % ---------------------------------------------------

   if OKtoProceed==1
      for counter=1:25
          xNew = (xMin + xMax)/2;
          yNew = feval(funcName,xNew,'show');
          if (yNew*yMin>0),  xMin=xNew; yMin=yNew; end;
          if (yNew*yMin==0), break, end;
          if (yNew*yMin<0),  xMax=xNew; yMax=yNew; end;
          if (abs(xMax-xMin)<tol*abs(xNew)), break; end;
      end; 
   % ---------------------------------------------------
   %        Display final bounds and function
   % ---------------------------------------------------

      set(handles.xmax, 'string',num2str(xMax));
      set(handles.ymax, 'string',num2str(yMax));
      set(handles.xmin, 'string',num2str(xMin));
      set(handles.ymin,'string',num2str(yMin));
	  
	  % Calculate best guess at final result
	  if (yMin~=yMax);
         x0 = (yMax*xMin - yMin*xMax)/(yMax-yMin);
      else
         x0 = (xMin+xMax)/2;
      end;

      OpenSolutionGraph;
      y0 = feval(funcName,x0,'final');

	  figure(Hf_hunt);
	  handles.E = x0;
	  set(gcf,'userdata',handles);
	  
   end;   % OKtoProceed==1

end; % if strcmp(action,'DoTheHunt')

% ------------------------------------------------------------------
%         PART 3A: DISPLAY VALUE OF YMAX
% ------------------------------------------------------------------

if strcmp(action,'ShowYmax')

   Hf_hunt  = gcf;
   handles  = get(Hf_hunt,'userdata');
   tol      = handles.tol;	  
   funcName = get(gcf,'tag');

   OpenSolutionGraph;
   xMax = str2num(get(handles.xmax,'string'));
   yMax = feval(funcName,xMax,'show');
   temp = gcf;         
   
   figure(Hf_hunt);
   set(handles.ymax,'String',num2str(yMax));
   set(gcf,'userdata',handles);

end; % if strcmp(action,'ShowYmax')

% ------------------------------------------------------------------
%         PART 3B: DISPLAY VALUE OF YMIN
% ------------------------------------------------------------------

if strcmp(action,'ShowYmin')

   Hf_hunt  = gcf;
   handles  = get(gcf,'userdata');
   tol      = handles.tol;	  
   funcName = get(gcf,'tag');

   OpenSolutionGraph;
   xMin = str2num(get(handles.xmin,'string'));
   yMin = feval(funcName,xMin,'show');
   temp = gcf;

   figure(Hf_hunt);
   set(handles.ymin,'String',num2str(yMin));
   set(gcf,'userdata',handles);

end; % if strcmp(action,'ShowYmin')

% ------------------------------------------------------------------
%         PART 4: EXPORT THE RESULT
% ------------------------------------------------------------------

if strcmp(action,'ExportResult')

   Hf_hunt  = gcf;
   handles  = get(gcf,'userdata');
   funcName = get(gcf,'tag');
   
   E = handles.E;
   set(handles.xmax,'string',num2str(E,8));
   set(handles.xmin,'string',num2str(E,8)); 
    
 % Display the final graph
   OpenSolutionGraph;
   cla;
   y0 = feval(funcName,E,'export');
 
   figure(Hf_hunt);
   set(handles.ymax,'string',num2str(y0));
   set(handles.ymin,'string',num2str(y0));

end; % if strcmp(action,'ExportResult')

% ------------------------------------------------------------------
%         PART 5: CLEAR THE DISPLAY
% ------------------------------------------------------------------

if strcmp(action,'ClearDisplay')

   Hf_hunt = gcf;
   handles = get(gcf,'userdata');
   set(handles.xmax, 'string','');
   set(handles.ymax, 'string','');
   set(handles.xmin, 'string','');  
   set(handles.ymin,'string','');
   
   OpenSolutionGraph;
   cla;
   figure(Hf_hunt);

end; % if strcmp(action,'ClearDisplay')

set(0,'ShowHiddenHandles','off');

return;
% ------------------------------------------------------------------
%                   END OF MAIN FUNCTION
% ------------------------------------------------------------------

% ******************************************************************
% ******************************************************************
% ******************************************************************


% ------------------------------------------------------------------
%                  SUBSIDIARY FUNCTIONS 
% ------------------------------------------------------------------
function thisHandle = OpenSolutionGraph

H_figs = get(0,'children');
thisHandle = findobj(H_figs,'flat','tag','eigenGraph');
% Note: the finder is tagged with the name 'eigenGraph'.
% If it's not there the figure will have to be initialized.
if length(thisHandle)==0
   thisHandle = figure('units','normalized', ...
                     'position',[0.36 0.20 0.60 0.40],...
                     'Name','Wave equation solution',...
				     'Tag','eigenGraph',...
				     'NumberTitle','off');
end;     % if length(Hf_graph)==0
figure(thisHandle);

return;

% ------------------------------------------------------------------
%               END OF SUBSIDIARY FUNCTIONS
% ------------------------------------------------------------------