Emerged since c++11, lambda expression/function is an unnamed function object capable of capturing variables in scope.
1. syntax of a lambda expression
[ captures ] <tparams>(optional)(c++20) ( params ) specifiers exception attr -> ret requires(optional)(c++20){ body }
[ captures ] ( params ) -> ret { body }
[ captures ] ( params ) { body }
[ captures ] { body }
examples:
[](){} //barebone lambda
[](){}() // immediately execute a lambda
auto print = [](const int& n) { n = n+1; std::cout << " " << n; };std::for_each(v.begin(), v.end(), print); // caller of the lambda expression
std::for_each(v.begin(), v.end(), [](int &n){ n++; });