What's New in C++23

Introduction

• Presenter: Software architect and project manager at Nikon Metrology (Belgium)
• Author of several books, including Professional C++ (5th edition)
• Founder of the Belgian C++ Users Group, organizes events
• Overview of C++23 features, focusing on high-level insights

Agenda

• Overview of new language features
• Overview of new standard library features
• Questions will be held at the end of the session

Core Language Features

Explicit Object Parameters

• Replaces implicit this pointer in member functions
• Allows ref-qualified member functions to be more obvious
• Example: class Cell { void setValue(Cell& self) { self.m_value = 42; } }
• Enables writing recursive lambda expressions

If Const Eval

• Syntax: if const eval a else b
• Simplifies compile-time evaluation checks
• More robust than isConstantEvaluated function

Multidimensional Subscript Operator

• Allows proper multidimensional indexing using operator[]
• Simplifies access to multidimensional data structures

Attributes on Lambda Expressions

• Attributes can now be placed before or after parentheses
• New placement modifies effects on the function call operator

New Integer Literal Surfaces

• Introduces UZ (size_t) and Z (signed size type)
• Improves type safety in integer operations

New Preprocessor Markers

• Introduces lifdef, lifendef for improved preprocessor directives
• New warning directive to emit compiler warnings

Unreachable Code

• Use std::unreachable to mark unreachable code sections
• Helps compiler optimize performance by omitting unnecessary checks

Compiler Optimizations

• Introduces standard assumptions to help optimize code
• Use [[assume]] syntax for performance hints

Example:

Standard Library Features

String Formatting Improvements

• New std::print and std::println simplify output operations
• Much faster than previous std::cout and std::format

New Containers

• Introduces flat_map, flat_set for optimized performance
• Uses underlying sequence containers for better memory management

std::span and md_span

• md_span supports multidimensional views and layout policies

Generators

• Standard coroutine generator for simplifying value sequences
• Example of a generator function iterating through values

Optional Monadic Operations

• New monadic operations (transform, and_then, or_else)
• Allows chaining operations without explicit checks for emptiness

Stack Traces

• Use std::stacktrace to retrieve current stack trace easily
• Can embed stack trace information in custom exceptions

Ranges

• New features: zip, pairwise, chunk, join, and more
• Enhancements for handling ranges and views

Expectation Type

• Introduces std::expected to represent value or error states
• Simplifies error handling in functions

Move-Only Functions

• std::move_only_function for lambdas with captured variables

Conclusion

• C++23 introduces many new features to enhance performance, usability, and expressiveness
• Encourages developers to explore and adopt new language features

Questions

• Open floor for questions
• Discussed implications of infinite views and performance optimization strategies.