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 Be sure that knowledge from this book won’t get outdated, as more and more Boost libraries become part of the C++ Standard.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

Evaluating metafunctions lazily


Lazy evaluation means that the function is not called until we really need its result. Knowledge of this recipe is highly recommended for writing good metafunctions. The importance of lazy evaluation will be shown in the following example.

Imagine that we are writing some metafunction that accepts a function Func, a parameter Param, and a condition Cond. The resulting type of that function must be a fallback type if applying the Cond to Param returns false, otherwise the result must be a Func applied to Param:

struct fallback;

template <
        class Func,
        class Param,
        class Cond,
        class Fallback = fallback>
struct apply_if; 

This metafunction is the place where we cannot live without lazy evaluation, because it may be impossible to apply Func to Param if the Cond is not met. Such attempts will always result in compilation failure and Fallback is never returned.

Getting ready

Reading Chapter 4, Compile-time Tricks, is highly recommended...