function structure = cbg2ese(system_name, system_type, system_cr, ...
    system_args, full_name, full_name_repetition, ...
    repetition,...
    structure, structure_file,infofilenum)
# Set up globals to count the component inputs and outputs. This relies on
# the named SS (the ports) being in the correct order. Using globals here
# avoids changing the common argument list for all _eqn files for something
# which is only used for named SS components.
  global local_u_index
  global local_y_index
  global at_top_level
# 
#     ###################################### 
#     ##### Model Transformation Tools #####
#     ######################################
# 
# Matlab function  cbg2ese.m
# Acausal bond graph to causal bond graph: mfile format
# Structure matrix [states,nonstates,inputs,outputs,zero_outputs]

# ###############################################################
# ## Version control history
# ###############################################################
# ## $Id$
# ## $Log$
# ## Revision 1.26  1998/08/24 14:53:55  peterg
# ## Uses new _cbg structure.
# ##
# ## Revision 1.25  1998/07/28 19:05:12  peterg
# ## Sttill has vector SS port bug?
# ##
# ## Revision 1.24  1998/07/27 10:26:02  peterg
# ## No change - but fixed bug in alias_args
# ##
# ## Revision 1.23  1998/07/08 12:33:51  peterg
# ## Reinstated the infofilenum parameter.
# ##
# ## Revision 1.22  1998/07/04 07:10:27  peterg
# ## Don't evaluate alias if no constitutive relationship or args and write
# ## message.
# ##
# ## Revision 1.21  1998/07/03 18:58:58  peterg
# ## Put arg alias stuff within function alias_args
# ## Called recursively to handle arithmetic expressions
# ##
# ## Revision 1.20  1998/07/03 14:39:09  peterg
# ## Added info messages a bit busy now!
# ##
# ## Revision 1.19  1998/04/12 11:58:19  peterg
# ## Rename port components by changing name_r to [name_r
# ##
# ## Revision 1.18  1998/04/11 18:59:16  peterg
# ## at_top_level now global - passed to SS components
# ##
# ## Revision 1.17  1998/04/04 10:47:31  peterg
# ## Uses (coerced) components from _cbg file - _abg not now used here.
# ##
# ## Revision 1.16  1998/03/06 09:38:58  peterg
# ## Now writes correct structure file for multiport C & I
# ##
# ## Revision 1.15  1997/12/16 18:24:33  peterg
# ## Added unknown_input to structure list
# ##
# ## Revision 1.14  1997/08/26 07:51:10  peterg
# ## Now counts the local input and outputs by order of appearence rather
# ## than by port number - it therfore handles ports with bicausality correctely.
# ##
# ## Revision 1.13  1997/05/19 16:45:56  peterg
# ## Fixed ISW bug -- deleted spurious ISW_eqn.m file
# ##
# ## Revision 1.12  1997/04/15  09:17:26  peterg
# ## Added the structure file - contains details of states etc.
# ## 
# ## Revision 1.11  1996/12/07 18:20:11  peterg
# ## Replaces null argument by a default and tells user.
# ##
# ## Revision 1.10  1996/12/07 17:37:07  peterg
# ## Now handles numbered SS ports appearing at top level.
# ##
# ## Revision 1.9  1996/12/04 21:49:47  peterg
# ## Compares full-name with empty string (instead of testing for zero
# ## length)
# ##
# ## Revision 1.8  1996/08/30  16:36:08  peter
# ## More info written to ese files.
# ##
# ## Revision 1.7  1996/08/30 11:23:13  peter
# ## Argument substitution implemented.
# ##
# ## Revision 1.6  1996/08/27  08:04:52  peterg
# ## Handles complex components and repetative components.
# ##
# ## Revision 1.5  1996/08/24  15:02:23  peter
# ## Writes `END;' to keep reduce happy.
# ##
# ## Revision 1.4  1996/08/19 09:03:41  peter
# ## Handles repeating components.
# ##
# ## Revision 1.3  1996/08/18 20:08:02  peter
# ## Included additional structure: structure(5) = zero_outputs.
# ##
# ## Revision 1.2  1996/08/08 18:08:11  peter
# ## Sorted out file naming sceme
# ##
# ## Revision 1.1  1996/08/08 15:53:23  peter
# ## Initial revision
# ##
# #############################################################

  system_name, system_type, full_name,

  pc = "%";

# Set up the names corresponding to the structure matrix.
  structure_name = [
		    "state        ",
		    "nonstate     ",
		    "input        ",
		    "output       ",
		    "zero_output  ",
		    "unknown_input"];

	
# Are we at the top level of the heirarchy?
  at_top_level = strcmp(full_name, "");

# Create the (full) system name
  if at_top_level
    full_name = system_name;
    full_name_repetition = system_name;
    system_type = system_name;
  else
    full_name = [full_name, "_", system_name];
    full_name_repetition = [full_name_repetition, ...
			    "_", system_name, "_", num2str(repetition)];
  end;
  
  

  cbg_name = [full_name, "_cbg"];
  if exist(cbg_name)~=2		# Return if cbg file doesn't exist
    disp([cbg_name, " does not exist"]);
    return
  end;
  
# Setup files
  ese_name = [full_name_repetition, "_ese.r"];
  ese_file = fopen(ese_name, "w");

  fprintf(ese_file, "\n%s%s Equation file for system %s (file %s)\n", ...
	  pc, pc, full_name_repetition, ese_name);
  fprintf(ese_file, "%s%s Generated by MTT\n\n", pc, pc);

# Evaluate the system function to get the bonds
  eval(["CBG = ", cbg_name, ";"]);
  #eval(["[bonds,status,system_type,components] = ", cbg_name, ";"]);
  abg_name = [system_type, "_abg"];
  cmp_name = [system_type, "_cmp"];
  alias_name = [system_type, "_alias"];

# No longer needed - cbg now has components:  
#  eval(["[junk,components]=", abg_name, ";"]);

  # Find number of bonds
  [n_bonds,columns] = size(CBG.bonds);
  if (columns ~= 2)&(n_bonds>0)
    error("Incorrect bonds matrix: must have 2 columns");
  endif;

#  # Find number of components
#  [n_components,columns] = size(components);
#  n_components = n_components
  
  # Set up the first dummy bond number - needed for repetative components
#  next_bond = max(max(abs(components)))+1;

  # Set up the counters for the labelled SS. These are, by definition,
  # encountered first and so the counters will not be messed up by subsystems.
  local_u_index = 0;
  local_y_index = 0;

  if (length(system_args)==0)
    mtt_info(sprintf("No arguments given so no argument aliasing done for system %s(%s)",\
		     system_name,system_type), infofilenum);
  endif;

  if (length(system_cr)==0)
    mtt_info(sprintf("No cr given so no cr aliasing done for system %s(%s)",\
		     system_name,system_type), infofilenum);
  endif;


  field=["ports";"subsystems"];	# Do for both ports and subsystems -
				# ports first
  for i=1:2
    if struct_contains(CBG,field(i,:));
      eval(["CBG_field = CBG.",field(i,:), ";"]);
      for [subsystem,comp_name] = CBG_field
				#comp = nozeros(components(i,:));
    	comp = subsystem.connections;
    	bond_list = abs(comp);
    	direction = sign(comp)'*[1 1];
				# Convert from arrow orientated to component orientated causality
    	comp_bonds = CBG.bonds(bond_list,:).*direction;
	
    	disp(["---- ", field(i,:), "Component ---"]);    
				# Get the component details
				#eval([ "[comp_type,comp_name,cr,args,repetitions] = ", cmp_name, "(i)"]);
    	
				# Alias the args list -- if not at top level
    	message = sprintf("\tfor component  %s (%s) within %s",\
			  comp_name,subsystem.type,full_name);    
    	if struct_contains(subsystem,"alias")
	  subsystem.arg = alias_args(subsystem.arg,subsystem.alias,";",message,infofilenum)
	  subsystem.cr = alias_args(subsystem.cr,subsystem.alias,";",message,infofilenum)
    	endif;

	
			# Substitute positional ($1 etc) arguments
    	subsystem.cr = subs_arg(subsystem.cr,system_cr, ...
				"lin",full_name,subsystem.type,comp_name,infofilenum);
    	subsystem.arg = subs_arg(subsystem.arg,system_args, ...
				 "1",full_name,subsystem.type,comp_name,infofilenum);
    	
				# change name of 0 and 1 components -- matlab doesn't like numbers here
    	if strcmp(subsystem.type,"0")
	  subsystem.type = "zero";
    	endif;
    	if strcmp(subsystem.type,"1")
	  subsystem.type = "one";
    	endif;
    	
    	ports = length(bond_list);
    	
    	if subsystem.repetitions>1
	  port_pairs = ports/2;
	  if round(port_pairs)~=port_pairs;
	    mtt_info(["Repeated component ", comp_name, ...
		      " has an odd number of ports - ignoring repetitions"], infofilenum);
	    subsystem.repetitions = 1;
	  endif;
    	endif;
    	
    	if subsystem.repetitions>1
	  odd_bonds = bond_list(1:2:ports-1);
	  even_bonds = bond_list(2:2:ports);
    	endif;
    	
    	for k = 1:subsystem.repetitions
	  
	  if subsystem.repetitions>1
	    
	    if k==1
	      bond_list(1:2:ports-1) = odd_bonds;
	    else
	      bond_list(1:2:ports-1) = bond_list(2:2:ports);
	    endif;
	    
	    if k==subsystem.repetitions
	      bond_list(2:2:ports) = even_bonds;
	    else
	      new_bonds = [next_bond:next_bond+port_pairs-1];
	      next_bond = next_bond+port_pairs;
	      bond_list(2:2:ports) = new_bonds;
	    endif;
	    
	  endif;
	  
				# Invoke the appropriate equation-generating procedure
	  name_r = full_name_repetition;
	  eqn_name = [subsystem.type, "_eqn"]
	  
	  if exist(eqn_name)~=2 # Try a compound component
	    disp("---PUSH---"); bond_list, comp_name, subsystem.type
	    structure = cbg2ese(comp_name, subsystem.type, subsystem.cr, subsystem.arg, ...
				full_name, full_name_repetition, ...
				k, structure,  structure_file, infofilenum);
	    
				# Link up the bonds
	    fprintf(ese_file, ...
		    "\n\t%s Equations linking up subsystem %s (%s)\n\n", ...
		    pc, comp_name, subsystem.type);
	    name_comp_name = sprintf("%s_%s_%d", ...
				     full_name_repetition, comp_name, k);
	    
	    printf("\n\t%s Equations linking up subsystem %s (%s)\n\n",\
		   pc, comp_name, subsystem.type);
	    bond_list
	    
	    u_index = 0; y_index = 0; # Count the inputs and outputs
	    for port_number=1:length(bond_list)
				# Effort
	      if comp_bonds(port_number,1)==1 # Source
	     	u_index = u_index + 1;
	     	fprintf(ese_file, "%s_MTTu%d := %s;\n", ...
		 	name_comp_name, u_index, varname(name_r, ...
							 bond_list(port_number),1));
	      else # Sensor
	     	y_index = y_index + 1;
	     	fprintf(ese_file, "%s := %s_MTTy%d;\n", ...
		 	varname(name_r, ...
				bond_list(port_number),1), name_comp_name, y_index);
	      end;
				# Flow
	      if comp_bonds(port_number,2)==-1 # Source
	     	u_index = u_index + 1;
	     	fprintf(ese_file, "%s_MTTu%d := %s;\n", ...
		 	name_comp_name, u_index, varname(name_r, ...
							 bond_list(port_number),-1));
	      else # Sensor
	     	y_index = y_index + 1;
	     	fprintf(ese_file, "%s := %s_MTTy%d;\n", ...
		 	varname(name_r, ...
				bond_list(port_number),-1), name_comp_name, y_index);
	      end;	
	    end;
	    
	    disp("---POP---");
	  else # its a simple component
	    fprintf(ese_file, "\n\t%s Equations for component %s (%s), repetition %d\n\n", ...
		    pc, comp_name, subsystem.type,k);
	    
	    
				# Is it a named port? (Name begins with [)
            Named_Port = (comp_name(1)=="[");
	    
	    if Named_Port #Add [ to start of name
	      name_r = ["[" name_r];
	    endif;
	    
				# Save the current structure
	    old_structure = structure;
	    
				# Generate the simple component equations
	    eval(["structure = ", ...
		  eqn_name, ...
		  "(name_r,bond_list,comp_bonds, ...
		    direction,subsystem.cr,subsystem.arg,structure,ese_file);" ]);
	    
				# If structure has changed, write info to structure file.
	    structure_change = structure-old_structure;
	    
				# The following line is to avoid probs with multiport C or I
				# it needs changing to handle multi ports correctly
	    structure_changes = sum(structure_change);
	    
	    structure_change = structure_change>zeros(size(structure_change));
 	    if structure_changes>0
 	      which_indices = getindex(structure_change,1);
 	      which_indices = which_indices(:,2)';
 	      for which_index=which_indices
 	    	value = structure(which_index);
	    	value_change=value-old_structure(which_index);
	    	for k=1:value_change
		  fprintf(structure_file, ...
			  "%s\t%1.0f\t%s\t%s\t%1.0f\n", ...
			  structure_name(which_index,:), value-k+1, ...
			  comp_name, full_name, repetition);
	    	endfor;
 	      endfor;
 	    endif;
	    
	  end;
    	end;
      endfor			# [subsystem,comp_name] = CBG_field
    endif			# struct_contains(CBG,field(i,:))
  endfor			# i=1:2
  # Close the files
  fclose(ese_file);

endfunction