Pointers

• is an object in its own right, unlike reference.
• also have two exceptios, the pointer and the object must match
• Note that it is possible for a pointer to an object and a pointer one past the end of a different object to hold the same address

Null Pointers

• ⭐️new standard introduce a literal nullptr.
• the literal 0.
• a preprocessor variable named NULL (in cstdlib header).

Attention

but can’t assign an int variable even if the value happens to be 0.

void* Pointers

The type void* is a special pointer type that can hold the address of any object.

• we can compare it to another pointer.
• we can pass it to or return it from a funtion.
• we can assign it to another pointer.
• we use a void * pointer to deal with memory as memory.

Pointers and const

Pointers to const

here const is a 🔗low-level const, so the pointer itself can change, but can’t change the underlain through the pointer.

int i = 0;
const int *p = i;

read from right to left: modifier indicates p is a pointer, and the base type says the pointer point to a const int.

const Pointers

here const is a 🔗top-level const, so the pointer itself cannot change, but can change the underlain through the pointer.

int i = 0;
int *const p = &i;
int const *p = &i;

again right from left.

Pointer Arithmetic

指针的加减法、比较等等，实际上是作为 iterators 时才有意义。而指针在数组中，是作为迭代器使用的，所以拥有迭代器的一切操作：

• compare
• addition
• subtraction of two pointers