cout << "Unsatisfied preconditions so far: " << _goal.size() << ": ";
copy(_goal.begin(), _goal.end(), ostream_iterator<string>(cout, " "));
cout << endl;
cout << "Unsatisfied preconditions so far: " << _goal.size() << ": ";
copy(_goal.begin(), _goal.end(), ostream_iterator<string>(cout, " "));
cout << endl;