Tree& Tree::operator+ (Tree& other_tree){
    Tree* first_tree = new Tree(*this);
    Tree* second_tree = new Tree(other_tree);

    if (first_tree->root != NULL){
        Node* parent_of_leaf = &(first_tree->findParentOfLeaf());
        if (!parent_of_leaf->isLeaf()){
            int number_of_child_leaf = parent_of_leaf->whichChildIsLeaf();
            delete parent_of_leaf->children[number_of_child_leaf];
            parent_of_leaf->children[number_of_child_leaf] = second_tree->root;
            first_tree->temporary = true;
            second_tree->temporary = true; //czy trzeba?
            return (*first_tree);
        }
        else{
            delete first_tree;
            second_tree->temporary = true;
            return *second_tree;
        }
    }
    else{
        second_tree->temporary = true;
        return *second_tree;
    }
}

Tree& Tree::operator=(Tree& other_tree){
    Node* copied_root = new Node(*other_tree.root);
    arguments.clear();
    errors.clear();
    if (root != NULL) {
        delete root;
        root = copied_root;
    }
    for (int i=0; i<other_tree.arguments.size(); i++){
        arguments.push_back(other_tree.arguments[i]);
    }
    for (int i=0; i<other_tree.errors.size(); i++){
        errors.push_back(other_tree.errors[i]);
    }
    if (other_tree.temporary) {
        delete &other_tree;
    }
    return (*this);
}