forma(varargin);

function [A] = forma(varargin);
%
% Estimates the formula matrix of the specified list of chemical species.
% It is possible to recognize 103 chemical elements.
%
% Created by A. Trujillo-Ortiz, R. Hernandez-Walls, K. Barba-Rojo
%            and A. Castro-Perez
%            Facultad de Ciencias Marinas
%            Universidad Autonoma de Baja California
%            Apdo. Postal 453
%            Ensenada, Baja California
%            Mexico.
%            [e-mail]
%
% Copyright. November 20, 2006.
%

persistent name;

if (isempty(name))
  name = {'H' ,'He','Li','Be','B' ,'C' ,'N' ,'O' ,'F' ,'Ne','Na','Mg',...
          'Al','Si','P' ,'S' ,'Cl','Ar','K' ,'Ca','Sc','Ti','V' ,'Cr',...
          'Mn','Fe','Co','Ni','Cu','Zn','Ga','Ge','As','Se','Br','Kr',...
          'Rb','Sr','Y' ,'Zr','Nb','Mo','Tc','Ru','Rh','Pd','Ag','Cd',...
          'In','Sn','Sb','Te','I' ,'Xe','Cs','Ba','La','Ce','Pr','Nd',...
          'Pm','Sm','Eu','Gd','Tb','Dy','Ho','Er','Tm','Yb','Lu','Hf',...
          'Ta','W' ,'Re','Os','Ir','Pt','Au','Hg','Tl','Pb','Bi','Po',...
          'At','Rn','Fr','Ra','Ac','Th','Pa','U' ,'Np','Pu','Am','Cm',...
          'Bk','Cf','Es','Fm','Md','No','Lr'}';
end
 
varargin = unpack(varargin);
A = zeros(length(name),length(varargin));
 
Species = varargin;
 
for i=1:length(varargin),
  [s,A(:,i)] = forve(varargin{i},A(:,i),name,1.0);
end
 
i = find(sum(A,2)>0);
A = A(i,:);
b = {name{i}}';

%Elements = b

function [out] = unpack(in);
out  = {};
for i=1:length(in);
  if (iscell(in{i}))
    tmp = unpack(in{i});
    out = {out{:},tmp{:}};
  else  
    out = {out{:},in{i}};
  end
end
 
function [s,b] = forve(s,b,name,factor)

coef = '';
sym = '';

while not(isempty(s)),
  next = s(end);
  s = s(1:end-1);
  if isletter(next)
    sym = strcat(next,sym);
    i = strmatch(sym,name,'exact');
    if any(i)
      b(i) = b(i) + factor*stoi(coef);
      coef = '';
      sym = '';
    end
  elseif isnumber(next)
    coef = strcat(next,coef);
    sym = emptystring(sym);
  elseif isright(next)
    [s,b] = forve(s,b,name,factor*stoi(coef));
    coef = '';
    sym = emptystring(sym);
  elseif isleft(next)
    sym = emptystring(sym);
    return;
  end
end

sym = emptystring(sym);
     
function [s] = emptystring(s)
if (not(isempty(s)))
  disp(['Unrecognized string: ',s]);
end
sym = '';
 
function [i] = isnumber(s)
i = or(and(ge(abs(s),48),le(abs(s),57)),eq(abs(s),46));

function [i] = isleft(s)
i = eq(abs(s),40);

function [i] = isright(s)
i = eq(abs(s),41);
 
function [n] = stoi(s)
if isempty(s)
  n = 1;
else
  n = str2num(s);
end