Usage of & in c++

In C, the & operator is used to obtain a reference: obtain an lvalue reference (modifiable value): & variable or expression. Get an rvalue reference (only values ​​can be read): & rvalue (temporary or expression result). Get function return type reference: & function name. Advantages of & operator: avoid copying and can modify the original value. Note: References need to be initialized, cannot point to null values, and have a consistent life cycle.

Usage of & operator in C

& Meaning of operator:

& Operator is used to get a reference. A reference is a data type that points directly to another variable rather than a copy of its value.

& Usage of operator:

& operator can be used in the following scenarios:

• Get lvalue Reference: Apply the & operator to a variable or expression and return an lvalue reference pointing to the variable or expression. An lvalue reference can modify the object it refers to.

For example:

int a = 10;
int& b = a;
b++; // 等价于 a++

• Getting an rvalue reference: Apply the & operator to an rvalue (such as a temporary value or expression result), Returns an rvalue reference pointing to this rvalue. An rvalue reference can only read the object it refers to, not modify it.

For example:

const int& c = 10; // c 是指向字面量 10 的右值引用

• Get a reference to the function return type: Apply the & operator to the function name to return a reference to the function return type .

For example:

int& foo(); // foo 返回指向 int 类型的左值引用

& Advantages of operator:

• Can avoid copying: Direct Manipulating references improves program efficiency by avoiding the creation of copies.
• The original value can be modified: An lvalue reference can modify the object it refers to, while an rvalue reference can only read.

& Notes on operators:

• References must be initialized: References must be initialized at declaration or assignment time.
• References cannot point to null values: References cannot point to null values ​​or undefined variables.
• A reference must have the same lifetime as the object it refers to: A reference must be valid for the lifetime of the object it refers to.

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