标准库的链接列表Node uses the Option type:
struct Node<T> {
next: Option<NonNull<Node<T>>>,
prev: Option<NonNull<Node<T>>>,
element: T,
}
并使用以下代码创建一个 node :
Node {
next: None,
prev: None,
element,
}
BTree中LeafNode的实现，标准库uses a raw pointer for the parent node:
struct LeafNode<K, V> {
parent: *const InternalNode<K, V>,
parent_idx: MaybeUninit<u16>,
len: u16,
keys: MaybeUninit<[K; CAPACITY]>,
vals: MaybeUninit<[V; CAPACITY]>,
}
并创建新的叶 node by setting parent to ptr::null:
LeafNode {
keys: MaybeUninit::uninitialized(),
vals: MaybeUninit::uninitialized(),
parent: ptr::null(),
parent_idx: MaybeUninit::uninitialized(),
len: 0
}
我们可以用nullptr来实现C++中的上述代码，那么Option和std::ptr::null()之间的区别是什么？建议用什么方式表示空指针？