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C++17 in Detail: A Deep Dive

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Introduction

Language Features Working With Maps Debug Printing Let's Start!

Removed or Fixed Language Features

Introduction Removed Elements Removing the 'register' Keyword Removing Deprecated Operator ++ (bool)Removing Deprecated Exception Specifications Removing Trigraphs Fixes static_assert With No Message Compiler Support

Removed And Deprecated Library Features

Introduction Removing auto_ptr Removed std::random_shuffle Removing Old functional Stuff `std::iterator` Is Deprecated Other Smaller Removed or Deprecated Items Compiler Support

Language Clarification

Introduction Expression Evaluation Order Evaluation Order in C++17 Guaranteed Copy Elision Named Return Value Optimization Non-movable/Non-copyable type Updated Value Categories Simplification of gl/prvalue Dynamic Memory Allocation for Over-Aligned Data Exception Specifications in the Type System Quiz Compiler Support

Templates

Introduction Template Argument Deduction for Class Templates Deduction Guides Fold Expressions Examples - Fold Expression if constexpr Template Code Simplification Examples - Template Code Simplifications Declaring Non-Type Template Parameters With auto Other Modifications in C++ 17 Quiz Compiler Support

General Language Features

Introduction Structured Binding Declarations The Syntax Modifiers & Limitations Binding Providing Structured Binding Interface for Custom Class Init Statement for if and switch Using if In A Search Statement Inline Variables How Can It Simplify The Code constexpr Lambda Functions Capturing [*this] in Lambda Expressions Nested Namespaces __has_include Preprocessor Expression Quiz Compiler Support

Standard Attributes

Introduction Why do we need attributes?Before C++11 Attributes in C++11/C++14 C++17 additions Third standard attribute Namespaces/enumerators attributes More on attributes Summary Quiz Compiler Support

std::optional

Introduction The Standard Library Changes A Basic Example Of std::optional std::optional Creation in_place Construction Default Construction Constructors With Many Arguments Returning std::optional Be Careful With Braces When Returning Accessing The Stored Value Operations on std::optional Examples Of std::optional Performance & Memory Consideration Special case: optional<bool> and optional<T*>Summary Quiz Compiler Support

std::variant

std::variant demo

When to Use std::variant

std::variant Creation

In Place Construction

Ambiguity and Complex Types

Changing the values

Object lifetime

Accessing Stored Value

Visitors for std::variant

Visiting Multiple Variants

Exception safety guarantees

Performance & Memory Considerations

Examples of std::variant

Parsing command line

Parsing and State Machines

Compiler Support

std::any

Introduction The Basics Object Creation Accessing The Stored Value Performance & Memory Considerations Migration from boost::any Summary Compiler Support

std::string_view

Introduction The Basics When to Use The std::basic_string_view Type std::string_view Creation Other Operations Risks Using string_view Problem With The Initial Example Reference Lifetime Extension Choosing between string & string_view Initializing string Members from string_view Handling Non-Null Terminated Strings Printing With printf()Conversion Functions Like atoi()/atof()General Solution Performance & Memory Considerations Strings in Constant Expressions Migration from boost::string_ref and boost::string_view Example: Working with Different String APIs Example: String Split Wrap Up Quiz Compiler Support

Searchers and String Matching

Introduction Overview of String Matching Algorithms New Algorithms Available in C++ 17 Using Searchers Examples - Using Searchers DNA Matching Summary Compiler Support

String Conversions

Introduction Elementary string conversions from_chars Examples to_chars The benchmark Summary Quiz Compiler Support

Filesystem

Introduction Overview Demo Example for Path Object The Path Object Path Composition The Directory Entry & Directory Iteration Supporting Functions File Permissions Error Handling & File Races Examples of using std:filesystem Summary Compiler Support

Parallel STL Algorithms

Introduction C++17's Parallelism Execution Policies Par/Seq Policy Usage Exceptions Algorithm Update For_Each and Reduce Algorithms More Algorithms Performance of Parallel Algorithms Benchmark I Benchmark II Processing Containers Erroneous Techniques in Parallel Algorithms Counting Elements Summary Quiz Compiler Support

Other Changes in the Library

Introduction std::byte Improvements for Maps and Sets Emplace Enhancements for Maps and Unordered Maps Return Type of Emplace Methods Sampling Algorithms New Mathematical Functions Shared Pointers and Arrays Non-member size(), data() and empty()constexpr Additions to the Standard Library std::scoped_lock Polymorphic Allocator Compiler Support

Refactoring with std::optional and std::variant

Introduction The Use Case The Tuple Version A Separate Structure With std::optional With std::variant Wrap Up

Enforcing Code Contracts With [[nodiscard]]

Introduction Where Can It Be Used?Everywhere?!How to Ignore [[nodiscard]]Summary

Replacing enable_if with if constexpr - Factory with Variable Arguments

Introduction With if constexpr Summary

How to Parallelise CSV Reader

Introduction Application Requirements The Serial Version The Core Parts Converting Lines into Records The OrderRecord Class Calculations Using Parallel Algorithms Data Size and Instruction Count Matters Parallel Data Conversion Parallel Calculations Tests Wrap Up & Discussion

Changing the values

This lesson addresses the ways of changing values of the variant.

We'll cover the following

- Changing Values of the variant

Changing Values of the variant

There are four ways to change the current value of the variant:

• the assignment operator

• emplace

• get and then assign a new value for the currently active type

• a visitor (you cannot change the type, but you can change the value of the current alternative)

The important part is to know that everything is type-safe and also that the object lifetime is honoured.

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