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Introduction

About This Course

New C++20 Features

Chapter Overview 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 Quiz: C++20 Features

General STL Features

Chapter Overview Use the New Span Class to Make Our 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 Quiz: General STL Features Challenge: Make Our Code Safer and Easier to Read

STL Containers

Chapter Overview 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 Quiz: STL Containers Challenge: Let's Play with Containers

Compatible Iterators

Chapter Overview Iterators Are Fundamental Create an Iterable Range Make Our 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 Quiz: Compatible Iterators Challenge: Reverse Everything in a String

Lambda Expressions

Chapter Overview Lambda Expressions 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 Quiz: Lambda Expressions Challenge: Output with Lambda Expressions

STL Algorithms

Chapter Overview 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 Quiz: STL Algorithms Challenge: Let's Dive into Algorithms

Strings, Streams, and Formatting

Chapter Overview 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 Quiz: Strings, Streams and Formatting Challenge: String With a Zero Space

Utility Classes

Chapter Overview 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 Quiz: Utility Classes Challenge: Let's Check Out the Type of Data

Concurrency and Parallelism

Chapter Overview 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 Quiz: Concurrency and Parallelism Challenge: Sleep in a Multithread Function Call

Using the File System

Chapter Overview

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

Quiz: Usage of the File System

Challenge: What's Inside a Path?

A Few More Ideas

Chapter Overview Create a Trie Class for Search Suggestions Implement Multiple Producers and Consumers Calculate the Error Sum of Two Vectors Build Our Own Algorithm: Split Leverage Existing Algorithms: Gather Remove Consecutive Whitespace Convert Numbers to Words Quiz: Trie, Gather Function, and White Space Removal Challenge: Remove Whatever is White!

Conclusion

C++20 STL Cookbook/

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Use Manipulation Functions with Path

Use Manipulation Functions with Path

Learn to use manipulation functions with path.

We'll cover the following...

How to do it
How it works

The filesystem library includes functions for manipulating the contents of path objects. In this recipe, we will consider a few of these tools.

How to do it

In this recipe, we examine some functions that manipulate the contents of path objects:

We start with the namespace directive and our formatter specialization. We do this in every recipe in this chapter:

namespace fs = std::filesystem;
template<>
struct std::formatter<fs::path>: std::formatter<std::string> {
    template<typename FormatContext>
    auto format(const fs::path& p, FormatContext& ctx) {
        return format_to(ctx.out(), "{}", p.string());
    }
};

We can get the current working directory with the current_path() function, which returns a path object:

cout << format("current_path: {}\n", fs::current_path());

Output:

current_path: /usr/include

The absolute() ...

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