C++11 lambda as member variable?

Question

Can lambda's be defined as class members?

For example, would it be possible to rewrite the code sample below using a lambda instead of a function object?

struct Foo {     std::function<void()> bar; }; 

The reason I wonder is because the following lambda's can be passed as arguments:

template<typename Lambda> void call_lambda(Lambda lambda) // what is the exact type here? {      lambda(); }  int test_foo() {     call_lambda([]() { std::cout << "lambda calling" << std::endl; }); } 

I figured that if a lambda can be passed as a function argument then maybe they can also be stored as a member variable.

After more tinkering I found that this works (but it's kind of pointless):

auto say_hello = [](){ std::cout << "Hello"; }; struct Foo {     typedef decltype(say_hello) Bar;     Bar bar;     Foo() : bar(say_hello) {} }; 

Answer 1

A lambda just makes a function object, so, yes, you can initialize a function member with a lambda. Here is an example:

#include <functional> #include <cmath>  struct Example {    Example() {     lambda = [](double x) { return int(std::round(x)); };   };    std::function<int(double)> lambda;  };