case state::binary : 
                                        if ( i != input.end() && ((*i)->type == state::value || (*i)->type == state::expression || (*i)->type == state::id ) ) {
                                            i1 = i ;
                                            ++i ;
                                            if ( i != input.end() && ((*i)->type == state::operation || (*i)->type == state::expression) && (*i)->token == *str_i) {
                                                node *o = *i ;
                                                ++i ;
                                                if ( i != input.end() && ((*i)->type == state::value  || (*i)->type == state::expression || (*i)->type == state::id ) ) {
                                                    o->left = *i1 ;
                                                    o->right = *i;
                                                    o->type = state::expression ;
                                                    input.erase(i1) ;
                                                    input.erase( find(input.begin(), input.end(), o->right ) ) ;
                                                    i = input.begin() ;
                                                    state = state::binary ;
                                                    ++count ;
                                                }
                                            }
                                        }
                                        else if ( i != input.end() ) {
                                            state = state::binary ;
                                            ++i ;
                                        }
                                        else if ( str_i != operators.end() ) {
                                            state = state::binary ;
                                            i = input.begin() ;
                                            ++str_i ;
                                        }
                                            else {
                                            state = state::quit ;
                                            
                                        }
                                        
                                        break ;