How do define anonymous functions in C++?

Question

Can I define functions in C++ inline? I am not talking about lambda functions, not the inline keyword that causes a compiler optimization.

Answer 1

C++11 added lambda functions to the language. The previous versions of the language (C++98 and C++03), as well as all current versions of the C language (C89, C99, and C11) do not support this feature. The syntax looks like:

[capture](parameters)->return-type{body} 

For example, to compute the sum of all of the elements in a vector:

std::vector<int> some_list; int total = 0; for (int i=0;i<5;i++) some_list.push_back(i); std::for_each(begin(some_list), end(some_list), [&total](int x) {   total += x; }); 

Answer 2

In C++11, you can use closures:

void foo() {    auto f = [](int a, int b) -> int { return a + b; };     auto n = f(1, 2); } 

Prior to that, you can use local classes:

void bar() {    struct LocalClass    {        int operator()(int a, int b) const { return a + b; }    } f;     int n = f(1, 2); } 

Both versions can be made to refer to ambient variables: In the local class, you can add a reference member and bind it in the constructor; and for the closure you can add a capture list to the lambda expression.