Introduction
Functions are a fundamental concept in programming; regardless of the topic we discuss, we end up writing functions. Trying to cover functions in a single chapter is not only hard but also not very rational. This book contains recipes related to functions in all the other chapters. This chapter, however, covers modern language features related to functions and callable objects, with a focus on lambda expressions, concepts from functional languages such as higher-order functions, and type-safe functions with a variable number of arguments.