Constant

#Programming/CPlusPlus

常量（constant） 是指不能改变的值。在 cpp 中，有两种类型常量：

命名常量（named constants）：有标识符的常量，也叫 符号常量（symbolic constants）
字面常量（literal constants）：没有标识符的常量

命名常量

在 cpp 中，命名常量有三种子类型：

const 关键词修饰的常量变量
- constexpr 关键词修饰的编译期（compile-time）常量
#define 定义的字符串替换宏
Enumerate 枚举常量

Introduction to constants

In programming, a constant is a value that may not be changed during the program’s execution.^[1]

C++ supports two different kinds of constants:

Named constants are constant values that are associated with an identifier. These are also sometimes called symbolic constants, or occasionally just constants.
Literal constants are constant values that are not associated with an identifier.

Types of named constants

There are three ways to define a named constant in C++:^[1:1]

Constant variables
Object-like macros with substitution text
Enumerated constants

What is literals?

Literals are values that are inserted directly into the code. Literals are sometimes called literal constants because their meaning cannot be redefined.^[2]