c++ - Why I cannot convert unique_ptr to a raw pointer in assignment? -

when writing simple binary search tree insertion, encountered compilation error in g++ 4.7

error: cannot convert ‘node_ptr {aka std::unique_ptr<node>}’ ‘node*’ in assignment 

for line node* n = root.get() in bst_insert function. don't understand why?

struct node;  typedef std::unique_ptr<node> node_ptr;  struct node {         node(int k) : key(k) {};         int key;         node_ptr left = nullptr;         node_ptr right = nullptr; };  void bst_insert(node_ptr& root, node_ptr z) {     node* p = nullptr;     node* n = root.get();     while (n != nullptr) {         p = n;         n = z->key < n->key ? n->left : n->right;     }     if (p == nullptr)         root = std::move(z);     else if (z->key < p->key)         p->left = std::move(z);     else p->right = std::move(z); } 

n = z->key < n->key ? n->left : n->right; 

this line. n->left , n->right std::unique_ptrs , trying assign unique ptr raw pointer. change line to:

n = z->key < n->key ? n->left.get() : n->right.get();