Book Image

C++17 STL Cookbook

By : Jacek Galowicz
Book Image

C++17 STL Cookbook

By: Jacek Galowicz

Overview of this book

C++ has come a long way and is in use in every area of the industry. Fast, efficient, and flexible, it is used to solve many problems. The upcoming version of C++ will see programmers change the way they code. If you want to grasp the practical usefulness of the C++17 STL in order to write smarter, fully portable code, then this book is for you. Beginning with new language features, this book will help you understand the language’s mechanics and library features, and offers insight into how they work. Unlike other books, ours takes an implementation-specific, problem-solution approach that will help you quickly overcome hurdles. You will learn the core STL concepts, such as containers, algorithms, utility classes, lambda expressions, iterators, and more, while working on practical real-world recipes. These recipes will help you get the most from the STL and show you how to program in a better way. By the end of the book, you will be up to date with the latest C++17 features and save time and effort while solving tasks elegantly using the STL.
Table of Contents (18 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
Index

Adding polymorphy by wrapping lambdas into std::function


Let's say we want to write an observer function for some kind of value, which might change sometimes, which then notifies other objects; like a gas pressure indicator, or a stock price, or something similar. Whenever the value changes, a list of observer objects should be called, which then react their way.

In order to implement this, we could store a range of observer function objects in a vector, which all accept an int variable as the parameter, which represents the observed value. We do not know what these function objects do in particular when they are called with the new value, but we also don't care.

Of what type will that vector of function objects be? The std::vector<void (*)(int)> type would be correct if we were capturing pointers to functions with signatures such as void f(int);. This would indeed also work with any lambda expression that does not capture any variables, such as [](int x) {...}. But a lambda expression...