Professional C++, 5th Edition

19Function Pointers, Function Objects, and Lambda Expressions

WHAT'S IN THIS CHAPTER?

• How to use function pointers
• How to use pointers to class methods
• How to use polymorphic function wrappers
• What function objects are and how to write your own
• Details of lambda expressions

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Functions in C++ are so-called first-class functions, as functions can be used in the same way as normal variables, such as passing them as arguments to other functions, returning them from other functions, and assigning them to variables. A term that often comes up in this context is a callback, representing something that can be called. It can be a function pointer or something that behaves like a function pointer, such as an object with an overloaded operator(), or an inline lambda expression. A class that overloads operator() is called a function object, or functor for short. Conveniently, the Standard Library provides a set of classes that can be used to create callback objects and to adapt existing callback objects. It's time to take a closer look at the concept of callbacks, because many of the algorithms explained in the next chapter accept such callbacks to customize their behavior.

FUNCTION POINTERS

You don't normally think about the location of functions ...