code: function fromBLC(source){
      var index = 0;
      return (function go(){
        if (source[index] === "0")
          return source[index+1] === "0"
            ? (index+=2, Lam(go()))
            : (index+=2, App(go(), go()));
        for (var i=0; source[index]!=="0"; ++i)
          ++index;
        return (++index, Var(i-1));
      })();
    }
docs: String -> Term Converts a binary lambda calculus string to a term.