The role and usage of const in c++

const stands for immutability in C and is used to force a variable, function parameter, or class member to remain constant so that its value cannot be modified while the program is running. Specific usage includes: modifying variables to force immutability, such as const int my_age = 30;; modifying function parameters to pass immutable values, such as void print_name(const string& name);; modifying class members to declare immutable variables, such as class Person {public: const string name;};.

The role and usage of const in C

const is a keyword in C, which is used to modify variables , function or class member, indicating that its value is a constant, that is, it cannot be modified.

Function:

• Enforce immutability: Ensure that the value of a variable or object remains unchanged throughout the running of the program.
• Improve code security: Enhance the robustness and reliability of your code by preventing accidental modifications.
• Enhance readability and maintainability: Clearly indicate that the value of a variable or object is a constant, making the code easier to understand and maintain.

Usage:

Variables:

const int my_age = 30; // 声明一个不可变整型变量

Function parameters:

void print_name(const string& name); // 声明一个接受不可变字符串参数的函数

Class members:

class Person {
public:
    const string name; // 声明一个类中的不可变成员变量
};

Note:

• const modifier must be placed before the variable or member, for example const int, const string&.
• Immutable variables must be assigned a value when initialized and cannot be modified thereafter.
• For references (&), the const modifier can be placed before or after the reference symbol, such as const string& (passing an immutable string passed by reference) or string& const (immutable string passed by reference). The latter usage is less common.
• The const modifier can only be applied to primitive types, object pointers, and references. It cannot be applied to arrays or structures.

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