1--Lambda expression
1-1--Basic usage
① [] is used to capture variables, generally used to use and modify external variables, and can be empty;
② (int a, int b) indicates the parameter list, which can be omitted;
③ -> int defines the return type, which can generally be omitted and let the compiler infer it automatically;
④ auto f means to assign the defined lambda expression to the object f, and auto is used to automatically infer the type;
The basic usage is as follows:
#include <iostream>
int main(int argc, char *argv[]){
auto f = [](int a, int b) -> int{
return a + b;
};
std::cout << f(1, 2) << std::endl;
return 0;
}1-2--Other usages
① Use and modify external variables
Modify (pass by reference) and use external variables by capturing variables:
#include <iostream>
int main(int argc, char *argv[]){
int M = 10, N = 20;
auto f = [&M, N](int a, int b){
std::cout << "N:" << N << std::endl; // 使用外部变量
M = 30; // 修改外部变量
return a + b;
};
std::cout << f(1, 2) << std::endl;
std::cout << "M: " << M << std::endl;
return 0;
}② Custom variables
Customize variables by capturing variables without appearing outside;
#include <iostream>
int main(int argc, char *argv[]){
int M = 10, N = 20;
auto f = [&M, N, c=3](int a, int b){
std::cout << "N:" << N << std::endl; // 使用外部变量
M = 30; // 修改外部变量
return (a + b) * c;
};
std::cout << f(1, 2) << std::endl;
std::cout << "M: " << M << std::endl;
return 0;
}