backtracking combinator

bt-search.coffee

# searches a combination of the given elements that matches toMatch
#  @param c array - initially empty, carries the current combination throught
#                   the recursion
#  @param els array - the predefined set of elements
#  @param toMatch string - the rest-string to be matched with the elements
#
#  @return an array of combinations that recursively match
searchCombination = (c, els, rest) ->
  return c if rest.length==0

  searchCombination(c.concat([el]), els, rest.slice(el.length)) \
      for el in els when rest.indexOf(el) == 0

# test
console.log(JSON.stringify(
  searchCombination(
    c=[],
    els=['H','He','Li','Be','B','C','N','O','F','Ne','L','Na','Mg','Al','Si','P','S','Cl','Ar','M','K','Ca','Sc','Ti','V','Cr','Mn','Fe','Co','Ni','Cu','Zn','Ga','Ge','As','Se','Br','Kr','N','Rb','Sr','Y','Zr','Nb','Mo','Tc','Ru','Rh','Pd','Ag','Cd','In','Sn','Sb','Te','I','Xe','O','Cs','Ba','Hf','Ta','W','Re','Os','Ir','Pt','Au','Hg','Tl','Pb','Bi','Po','At','Rn','P','Fr','Ra','Rf','Db','Sg','Bh','Hs','Mt','Ds','Rg','Cn','Uut','Uuq','Uup','Uuh','Uus','Uuo','Q','La','Ce','Pr','Nd','Pm','Sm','Eu','Gd','Tb','Dy','Ho','Er','Tm','Yb','Lu','Ac','Th','Pa','U','Np','Pu','Am','Cm','Bk','Cf','Es','Fm','Md','No','Lr'],
    rest='FNORD'
  )
))

bt-search.js

(function() {
  var c = [], 
      els = ['H','He','Li','Be','B','C','N','O','F','Ne','L','Na','Mg','Al','Si','P','S','Cl','Ar','M','K','Ca','Sc','Ti','V','Cr','Mn','Fe','Co','Ni','Cu','Zn','Ga','Ge','As','Se','Br','Kr','N','Rb','Sr','Y','Zr','Nb','Mo','Tc','Ru','Rh','Pd','Ag','Cd','In','Sn','Sb','Te','I','Xe','O','Cs','Ba','Hf','Ta','W','Re','Os','Ir','Pt','Au','Hg','Tl','Pb','Bi','Po','At','Rn','P','Fr','Ra','Rf','Db','Sg','Bh','Hs','Mt','Ds','Rg','Cn','Uut','Uuq','Uup','Uuh','Uus','Uuo','Q','La','Ce','Pr','Nd','Pm','Sm','Eu','Gd','Tb','Dy','Ho','Er','Tm','Yb','Lu','Ac','Th','Pa','U','Np','Pu','Am','Cm','Bk','Cf','Es','Fm','Md','No','Lr'],
      rest = 'PUNK',
      searchCombination;

  searchCombination = function(c, els, rest) {
    var el, _i, _len, _results;
    if (rest.length === 0) return c;
    _results = [];
    for (_i = 0, _len = els.length; _i < _len; _i++) {
      el = els[_i];
      if (rest.indexOf(el.toUpperCase()) === 0) {
        _results.push(searchCombination(c.concat([el]), els, rest.slice(el.length)));
      }
    }
    return _results;
  };

  console.log(JSON.stringify(searchCombination(c, els, rest)));

}).call(this);