Book Image

C++20 STL Cookbook

By : Bill Weinman

Book Image

C++20 STL Cookbook

By: Bill Weinman

Overview of this book

Fast, efficient, and flexible, the C++ programming language has come a long way and is used in every area of the industry to solve many problems. The latest version C++20 will see programmers change the way they code as it brings a whole array of features enabling the quick deployment of applications. This book will get you up and running with using the STL in the best way possible. Beginning with new language features in C++20, this book will help you understand the language's mechanics and library features and offer insights into how they work. Unlike other books, the C++20 STL Cookbook takes an implementation-specific, problem-solution approach that will help you overcome hurdles quickly. You'll learn core STL concepts, such as containers, algorithms, utility classes, lambda expressions, iterators, and more, while working on real-world recipes. This book is a reference guide for using the C++ STL with its latest capabilities and exploring the cutting-edge features in functional programming and lambda expressions. By the end of the book C++20 book, you'll be able to leverage the latest C++ features and save time and effort while solving tasks elegantly using the STL.

Preface

About this book

Who this book is for

What this book covers

Conventions used

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Chaper 1: New C++20 Features

Chaper 1: New C++20 Features

Technical requirements

Format text with the new format library

Use compile-time vectors and strings with constexpr

Safely compare integers of different types

Use the "spaceship" operator <=> for three-way comparisons

Easily find feature test macros with the <version> header

Create safer templates with concepts and constraints

Avoid re-compiling template libraries with modules

Create views into containers with ranges

Free Chapter

Chapter 2: General STL Features

Chapter 2: General STL Features

Technical requirements

Use the new span class to make your C-arrays safer

Use structured binding to return multiple values

Initialize variables within if and switch statements

Use template argument deduction for simplicity and clarity

Use if constexpr to simplify compile-time decisions

Chapter 3: STL Containers

Chapter 3: STL Containers

A quick overview of the STL container types

Technical requirements

Use uniform erasure functions to delete items from a container

Delete items from an unsorted vector in constant time

Access vector elements directly and safely

Keep vector elements sorted

Efficiently insert elements into a map

Efficiently modify the keys of map items

Use unordered_map with custom keys

Use set to sort and filter user input

A simple RPN calculator with deque

A word frequency counter with map

Find long sentences with a vector of vectors

A ToDo list using multimap

Chapter 4: Compatible Iterators

Chapter 4: Compatible Iterators

Iterators are fundamental

Technical requirements

Create an iterable range

Make your iterators compatible with STL iterator traits

Use iterator adapters to fill STL containers

Create a generator as iterators

Use reverse iterator adapters to iterate backward

Iterate objects of unknown length with a sentinel

Build a zip iterator adapter

Create a random-access iterator

Chapter 5: Lambda Expressions

Chapter 5: Lambda Expressions

Lambda expressions

Technical requirements

Use lambdas for scoped reusable code

Use lambdas as predicates with the algorithm library

Use std::function as a polymorphic wrapper

Concatenate lambdas with recursion

Combine predicates with logical conjunction

Call multiple lambdas with the same input

Use mapped lambdas for a jump table

Chapter 6: STL Algorithms

Chapter 6: STL Algorithms

Technical requirements

Copy from one iterator to another

Join container elements into a string

Sort containers with std::sort

Modify containers with std::transform

Find items in a container

Limit the values of a container to a range with std::clamp

Sample data sets with std::sample

Generate permutations of data sequences

Merge sorted containers

Chapter 7: Strings, Streams, and Formatting

Chapter 7: Strings, Streams, and Formatting

String formatting

Technical requirements

Use string_view as a lightweight string object

Concatenate strings

Transform strings

Format text with C++20's format library

Trim whitespace from strings

Read strings from user input

Count words in a file

Initialize complex structures from file input

Customize a string class with char_traits

Parse strings with Regular Expressions

Chapter 8: Utility Classes

Chapter 8: Utility Classes

Technical requirements

Manage optional values with std::optional

Use std::any for type safety

Store different types with std::variant

Time events with std::chrono

Use fold expressions for variadic tuples

Manage allocated memory with std::unique_ptr

Share objects with std::shared_ptr

Use weak pointers with shared objects

Share members of a managed object

Compare random number engines

Compare random number distribution generators

Chapter 9: Concurrency and Parallelism

Chapter 9: Concurrency and Parallelism

Technical requirements

Sleep for a specific amount of time

Use std::thread for concurrency

Use std::async for concurrency

Run STL algorithms in parallel with execution policies

Share data safely with mutex and locks

Share flags and values with std::atomic

Initialize threads with std::call_once

Use std::condition_variable to resolve the producer-consumer problem

Implement multiple producers and consumers

Chapter 10: Using the File System

Chapter 10: Using the File System

Technical requirements

Specialize std::formatter for the path class

Use manipulation functions with path

List files in a directory

Search directories and files with a grep utility

Rename files with regex and directory_iterator

Create a disk usage counter

Chapter 11: A Few More Ideas

Chapter 11: A Few More Ideas

Technical requirement

Create a trie class for search suggestions

Calculate the error sum of two vectors

Build your own algorithm: split

Leverage existing algorithms: gather

Remove consecutive whitespace

Convert numbers to words

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Copy from one iterator to another

The copy algorithms are generally used to copy from and to containers, but in fact, they work with iterators, which is far more flexible.

How to do it…

In this recipe, we will experiment with std::copy and std::copy_n to get a good understanding of how they work:

Let's start with a function to print a container:

void printc(auto& c, string_view s = "") {
    if(s.size()) cout << format("{}: ", s);
    for(auto e : c) cout << format("[{}] ", e);
    cout << '\n';
}

In main(), we define a vector and print it with printc():

int main() {
    vector<string> v1
        { "alpha", "beta", "gamma", "delta", 
          "epsilon" };
   ...