About pointers and references

1. Similarities and differences

Both the reference and the pointer are composite types (compound type), based on the existing type

A reference is a binding to an object, an alias to an object, not a specific object, a pointer to an object, a pointer itself an object

References must be initialized at the time of definition, and only one object cannot be modified; The pointer does not require initialization when it is defined, and the pointer can change the object pointed to

2. Initialization

Initialization of the reference:

1 int 3  2int &ra = A; 3 ++ra;   // a=4

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Initialization of the pointer:

1 int 4 ; 2 int *PB = &b;

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The pointer is initialized to NULL:

1 int 0 ; 2 int *p2 = nullstr; 3 int *p3 = NULL; // #include <cstdlib>

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Note: Initialize the pointer with the literal value of 0 , the following two scenarios:

1 int 0 ; 2 Const int 0 ; 3 int *pa = i;         // Error 4 int *PB = j;         // OK

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3. Reference to reference, pointer to pointer, reference to reference pointer and pointer

referenced reference: Because the reference itself is not a specific object, there is no reference to the reference

1 int 1 ; 2 int &ri = i; 3 int &rii = ri;     // OK 4 int& &riii = ri;   // Error

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Referring to a reference, first a reference, and then referencing the object is a reference, so parse int& &riii = ri; left side analysis from right to left &rii is a reference, int& the referenced object is a int Types of References

Pointer pointer: The pointer itself is an object, so you can define a pointer to the pointer

1 intx =0;2 int*PX = &x;3 int**pxx = &px;4 5cout << x <<" "<< *px <<" "<< **pxx <<Endl;6cout << &x <<" "<< px <<Endl;7cout << &px <<" "<< pxx << Endl;

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Pointer to reference : As with referenced references, it is clear that pointers to references do not exist

1 int& *p = &ra;

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reference to the pointer :

1 intA =1;2 int*PA = &A;3 int* &rpa =PA;4 5  6cout << PA <<" "<< RPA <<Endl;7cout << *pa <<" "<< *rpa <<Endl;8*rpa =2;9cout << a << Endl;

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Note: For the definition of a more complex variable, the right-to-left analysis method on the left side of the assignment operator is relatively clear

4. About void*

The void* pointer can hold an address of any data type, and other types of pointers can only point to objects of the same type

About pointers and references