Modern C++ Programming Cookbook

How to do it...

In order to write a recursive lambda function, you must perform the following:

• Define the lambda in a function scope.
• Assign the lambda to an std::function wrapper.
• Capture the std::function object by reference in the lambda in order to call it recursively.

The following are examples of recursive lambdas:

• A recursive Fibonacci lambda expression in the scope of a function that is invoked from the scope where it is defined:

        void sample()         {           std::function<int(int const)> lfib =              [&lfib](int const n)             {               return n <= 2 ? 1 : lfib(n - 1) + lfib(n - 2);             };           auto f10 = lfib(10);         }

• A recursive Fibonacci lambda expression returned by a function, that can be invoked from any scope:

 std::function<int(int const)> fib_create() ...