1 lambda表达式定义
lambda_declearation.png
2 lambda [] 使用
lambda_capture.png
[&epsilon] capture by reference
[&] captures all variables used in the lambda by reference
[=] captures all variables used in the lambda by value
[&, epsilon] captures variables like with [&], but epsilon by value
[=, &epsilon] captures variables like with [=], but epsilon by reference
