Constant pointer, pointer constant

C Constant pointers in languages 、 Pointer constant in lua Application in

A constant pointer is a pointer to a constant , There are two ways to define it .

const int* n;

int const* n;

We need to pay attention to two points ：

1、 Constant pointer means that the value of a variable cannot be changed through this pointer , But you can still change the value of the variable through other references .

int a=5;

const int* n=&a;

a=6;

2、 The value that the constant pointer points to cannot be changed , But that doesn't mean the pointer itself can't change , Constant pointers can point to other addresses .

int a=5;

int b=6;

const int* n=&a;

n=&b;

Pointer constant means that the pointer itself is a constant , Can't point to another address , It is written as follows ：

int*const n;

It should be noted that , The address that the pointer constant points to cannot be changed , But the value stored in the address can be changed , It can be modified by other pointers to address change .

int a=5;

int*p=&a;

int* const n=&a;

*p=8;

The key to distinguish a constant pointer from a pointer constant is the position of the asterisk , We use the asterisk as the dividing line , If const To the left of the asterisk , Is a constant pointer , If const To the right of the asterisk is the pointer constant . If we read the asterisk as ‘ The pointer ’, take const pronounce as ‘ Constant ’ Words , The content is just in line with .int const * n; It's a constant pointer ,int *const n; It's a pointer constant .

Constant pointer to constant

const int* const a;

It's a combination of the two , The position that the pointer points to cannot be changed and the value of the variable cannot be changed through this pointer , But you can still change the value of the variable through other normal pointers .

const int* const luaX_tokens [];

stay lua In the source code, a constant array is implemented in this way , Defines a constant pointer to this constant array .