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?

Answer 1

Templates make it possible without type erasure, but that's it:

template
struct foo {
    T t;
};

template
foo::type>
make_foo(T&& t)
{
    return { std::forward(t) };
}

// ...
auto f = make_foo([] { return 42; });

Repeating the arguments that everyone has already exposed: []{} is not a type, so you can't use it as e.g. a template parameter like you're trying. Using decltype is also iffy because every instance of a lambda expression is a notation for a separate closure object with a unique type. (e.g. the type of f above is not foo.)