C++ decltype总结

decltype 的中英文对照总结：

中文	English
概念	Concept
decltype 是 C++11 引入的关键字，用于在编译期获取表达式的类型。	decltype is a keyword introduced in C++11 that obtains the type of an expression at compile time.
它能够准确推导表达式的类型，包括常量、引用、指针等属性。	It accurately deduces the type of an expression, including constness, references, and pointers.
定义	Definition
语法：decltype(expression) varName;	Syntax: decltype(expression) varName;
返回表达式的类型，用于声明变量或函数返回值类型。	Returns the type of the expression, used for declaring variables or function return types.
用途	Usage
- 类型推断，获取复杂表达式的精确类型。	- Type deduction to get the exact type of complex expressions.
- 避免重复书写类型，减少错误。	- Avoids manual repetition of types and reduces errors.
- 模板编程中根据表达式类型推断实现通用代码。	- Enables generic code in templates by deducing types from expressions.
- 与 auto 结合，能区分引用与非引用类型。	- Works with auto to distinguish between reference and non-reference types.
运行时执行	Runtime Execution
decltype 仅在编译期起作用，不会在运行时执行或产生代码。	decltype works only at compile time and does not execute or generate code at runtime.

---

示例 Example

int x = 10;

int& ref = x;

decltype(x) a = x;    // a 是 int 类型 / a is of type int

decltype(ref) b = x;  // b 是 int& 类型 / b is of type int&

---