C++ Concepts: Usage Guide

In C++20, Concepts are a new language feature used to define type requirements and constraints. They can be applied to constrain the parameter types of function templates, class templates, and regular functions to ensure that the parameter types meet specific requirements.

Concepts can be used to describe the interface of a class or function, specifying the member functions, type members, function signatures, and so on that parameters must have. Using concepts can improve code readability and maintainability, while also providing better error checking and hints at compile time.

Here is a simple example demonstrating how to use Concepts in C++ to define a basic type requirement:

template <typename T>
concept Numeric = std::is_arithmetic_v<T>;

template <Numeric T>
T add(T a, T b) {
    return a + b;
}

int main() {
    int result = add(2, 3); // 编译通过
    // float result = add(2.5, 3.5); // 编译错误，float不符合Numeric要求
    return 0;
}

In the above example, we defined a Concept named Numeric, which requires parameters to be arithmetic types. Then we defined a function template add, which only accepts parameter types that satisfy the requirements of Numeric. Finally, in the main function, we can see that calling add with an int parameter is legal, while passing in a float parameter will result in a compilation error. This demonstrates the usage of Concepts in C++.