lambda expressions

The new C++11 feature of lambda expressions provides the possibility to create unnamed function objects capable of capturing variables in scope.

[ captures ] ( params ) -> ret { body }

The capture list [] allows to specify what is visible in the function body:

[] : no variables visible

[var1, var2] : listed variables

[&] : all variables by reference

[=] : all variables by value

Specifying a return type is optional. The type of the lambda function itself is unique and unnamed:

  auto f = [](int a, int b) {return a * b;};

  decltype(f) g = f; // decltype determines the type of f
  cout << g(2, 3) << endl;

In-place function definitions can be useful as parameters for other functions:

std::vector<int> v{-8,3,5};
std::sort(v.begin(), v.end(), [](int x, int y) { return abs(x) < abs(y); });