Const and pointers in C + +

Const modifier

When you use the const modifier variable, the value of the variable is not modifiable and therefore needs to be initialized.

For example const int s = 0;

At this point s is the variable with the value immutable.

So based on this, there are three things when the const modifier pointer is:

(1) const int *p;

The const modifier is *p instead of p, so the value of *p is immutable, and the value of p is variable, so p is not initialized.

For example

int s = 0,t = 1;

const int *p;

p = &s;

cout<<*p<<endl;

p = &t;

cout<<*p<<endl;

The above code output:

0

1

But at this point, no matter p points to s or T, you cannot modify the value of the variable p points to by *p, such as *p = 2; (This is wrong because Const modifies the *p, and *p is immutable at this time)

(2) int *const p = &s;

At this point the position of the * is in front of the const, and the const directly modifies p, so the point of P is fixed and immutable, so it must be initialized.

At this point, however, you can still modify the value of the variable that p points to by *p.

For example, int s = 0;

int * Const P = &s;

cout<<*p<<endl;

*p = 3;

cout<<*p<<endl;

The above code output is:

0

3

(3) const int *const p = &s

In this case, both P and *p are immutable, so initialization must be required.

The third situation is actually the combination of the first two cases, it is not specifically analyzed.

Const and pointers in C + +