Book Image

Template Metaprogramming with C++

By : Marius Bancila
Book Image

Template Metaprogramming with C++

By: Marius Bancila

Overview of this book

Learn how the metaprogramming technique enables you to create data structures and functions that allow computation to happen at compile time. With this book, you'll realize how templates help you avoid writing duplicate code and are key to creating generic libraries, such as the standard library or Boost, that can be used in a multitude of programs. The introductory chapters of this book will give you insights into the fundamentals of templates and metaprogramming. You'll then move on to practice writing complex templates and exploring advanced concepts such as template recursion, template argument deduction, forwarding references, type traits, and conditional compilation. Along the way, you'll learn how to write variadic templates and how to provide requirements to the template arguments with C++20 constraints and concepts. Finally, you'll apply your knowledge of C++ metaprogramming templates to implement various metaprogramming patterns and techniques. By the end of this book, you'll have learned how to write effective templates and implement metaprogramming in your everyday programming journey.
Table of Contents (16 chapters)
1
Part 1: Core Template Concepts
5
Part 2: Advanced Template Features
9
Part 3: Applied Templates
Appendix: Closing Notes

Exploring generic lambdas and lambda templates

Lambdas, which are formally called lambda expressions, are a simplified way to define function objects in the place where they are needed. This typically includes predicates or comparison functions passed to algorithms. Although we will not discuss lambda expressions in general, let's take a look at the following examples:

int arr[] = { 1,6,3,8,4,2,9 };
std::sort(
   std::begin(arr), std::end(arr),
   [](int const a, int const b) {return a > b; });
int pivot = 5;
auto count = std::count_if(
   std::begin(arr), std::end(arr),
   [pivot](int const a) {return a > pivot; });

Lambda expressions are syntactic sugar, a simplified way of defining anonymous function objects. When encountering a lambda expression, the compiler generates a class with a function-call operator. For the previous example, these could look as follows:

struct __lambda_1
{
   ...