...one of the most highly
regarded and expertly designed C++ library projects in the
world. — Herb Sutter and Andrei
Up until now, the most basic ingredient is missing: creation of and access to local variables in the stack. When recursion comes into play, you will soon realize the need to have true local variables. It may seem that we do not need this at all since an unnamed lambda function cannot call itself anyway; at least not directly. With some sort of arrangement, situations will arise where a lambda function becomes recursive. A typical situation occurs when we store a lambda function in a Boost.Function, essentially naming the unnamed lambda.
There will also be situations where a lambda function gets passed as an argument to another function. This is a more common situation. In this case, the lambda function assumes a new scope; new arguments and possibly new local variables.
This section deals with local variables and nested lambda scopes.