Book Image

Boost C++ Application Development Cookbook - Second Edition

By : Anton Polukhin Alekseevic
Book Image

Boost C++ Application Development Cookbook - Second Edition

By: Anton Polukhin Alekseevic

Overview of this book

If you want to take advantage of the real power of Boost and C++ and avoid the confusion about which library to use in which situation, then this book is for you. Beginning with the basics of Boost C++, you will move on to learn how the Boost libraries simplify application development. You will learn to convert data such as string to numbers, numbers to string, numbers to numbers and more. Managing resources will become a piece of cake. You’ll see what kind of work can be done at compile time and what Boost containers can do. You will learn everything for the development of high quality fast and portable applications. Write a program once and then you can use it on Linux, Windows, MacOS, Android operating systems. From manipulating images to graphs, directories, timers, files, networking – everyone will find an interesting topic. Be sure that knowledge from this book won’t get outdated, as more and more Boost libraries become part of the C++ Standard.
Table of Contents (19 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Using an unordered set and map


In the previous recipe, we saw how string comparison can be optimized using hashing. After reading it, the following question may arise: can we make a container that will cache hashed values to use faster comparison?

The answer is yes, and we can do much more. We may achieve almost constant search, insertion, and removal times for elements.

Getting ready

Basic knowledge about C++ and STL containers are required. Reading the previous recipe will also help.

How to do it...

This will be the simplest of all recipes:

  1. All you need to do is just include the <boost/unordered_map.hpp> header, if you wish to use maps. If we wish to use sets, include the <boost/unordered_set.hpp> header.
  2. Now, you are free to use boost::unordered_map instead of std::map and boost::unordered_set instead of std::set:
#include <boost/unordered_set.hpp>
#include <string>
#include <cassert>

void example() {
    boost::unordered_set<std::string> strings;

    strings...