function structure =  SS_eqn(bond_number,bonds,direction,cr,args, ...
                            structure,filenum);

% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %% Version control history
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %% $Id$
% %% $Log$
% %% Revision 1.2  1996/08/08 16:38:19  peter
% %% Changed to filenumer type of fprintf
% %%
% %% Revision 1.1  1996/08/08 16:19:08  peter
% %% Initial revision
% %%
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


% The string 'cr' contains the effort attributes;  
% 'arg' contains the flow attributes. 
% external indicates an external variable
% internal indicates an internal variable
% anything else is the name of a constant.
% Blank is taken to be external

effort_attribute = cr;
flow_attribute = args;

if length(effort_attribute)==0
  effort_attribute = 'external';
end;

if length(flow_attribute)==0
  flow_attribute = 'external';
end;

inputs = structure(3);
outputs = structure(4);

% Effort
if strcmp(effort_attribute, 'external')
  if bonds(1,1)==-1 % Source