Introducing C++

Chapter 6. Lambdas and the Ranges Library

You used a few algorithms in Chapter 5. Some take a function, and you used a handwritten negative function to find negative numbers. Using a named function is fine, but C++ provides alternatives. For example, you also used function objects, including std::greater. C++ gives you another way to provide functions to algorithms: using lambdas, or anonymous (unnamed) functions. Lambdas offer a concise way to write short functions, letting you write the predicates and other functions directly in the call to the standard algorithms.

This chapter will show you how to write lambdas and give you further practice using algorithms. You used some range algorithms in the previous chapter. Ranges also offer several library features, including views, so you’ll see how to use some of these. You’ll also learn in this chapter how to use lambdas for more than the standard library algorithms.

In Chapter 5, you wrote a function called get_prices in main, in Example 5-3. This used the get_number function you defined in input.cpp. In this chapter, you will write a more general-purpose get_prices function, which you can use in subsequent chapters, as well as a couple of trading strategies. They won’t make you much money but will show you more C++. By the end of this chapter, your analysis and input source files will be more useful, and from there, Chapter 7 will show you how to generate prices rather than typing them in.

Removing Negative Numbers Using a Lambda ...