April 2023

Functional exception-less error handling with C++23’s optional and expected -- Sy Brand

std::optional has been updated in C++23, and std::expected added as a new way of representing errors in your code. Read more about them here:

Functional exception-less error handling with C++23’s optional and expected

by Sy Brand

From the article:

std::optional<T> expresses “either a T or nothing”. C++23 comes with a new type, std::expected<T,E> which expresses “either the expected T, or some E telling you what went wrong”. This type also comes with that special new functional interface. As of Visual Studio 2022 version 17.6 Preview 3, all of these features are available in our standard library. Armed with an STL implementation you can try yourself, I’m going to exhibit how to use std::optional‘s new interface, and the new std::expected to handle disappointments.

Simple Usage of C++20 Modules -- Victor Zverovich

SimpleUsage-Zverovich.jpgIn my previous post I showed how to compile {fmt} as a C++20 module with clang. Although taking only two commands, ideally it’s not something you should be doing manually. So in this post, I’ll talk about module support in CMake, everyone’s favorite not a build system.

Simple Usage of C++20 Modules

by Victor Zverovich

From the article:

My first attempt was to use the CMake’s built-in functionality advertised in “import CMake; C++20 Modules”. And after some struggle I made it to work with clang but unfortunately it was very limited. Here are some of the problems and limitations that I discovered:

  1. It only worked with ninja and while I don’t have anything against this build system it’s an extra hassle to get this additional dependency installed while make is usually available by default. This restriction also likely means that you cannot use such a CMake config with IDEs.
  2. Native CMake support only worked with clang 16 while the fmt module can be built manually with clang 15.
  3. It required the latest version of CMake and a lot of ceremony to set up, including some incomprehensible things.
  4. There were issues in dynamic dependency extraction both in clang-scan-deps and CMake itself.


Functional Exception-less Error Handling with C++23’s Optional and Expected -- Sy Brand

This post is an updated version of an article from five years ago, now that everything Sy talked about is in the standard and implemented in Visual Studio.

Functional Exception-less Error Handling with C++23’s Optional and Expected

by Sy Brand

From the article:

In software things can go wrong. Sometimes we might expect them to go wrong. Sometimes it’s a surprise. In most cases we want to build in some way of handling these misfortunes. Let’s call them disappointments.

std::optional was added in C++17 to provide a new standard way of expressing disappointments and more, and it has been extended in C++23 with a new interface inspired by functional programming.

C++23’s New Fold Algorithms -- Sy Brand

This post explains the benefits of the new “rangified” algorithms, talks you through the new C++23 additions, and explores some of the design space for fold algorithms in C++.

C++23’s New Fold Algorithms

by Sy Brand

From the article:

C++20’s algorithms make several improvements to the old iterator-based ones. The most obvious is that they now can take a range instead of requiring you to pass iterator pairs. But they also allow passing a “projection function” to be called on elements of the range before being processed, and the use of C++20 concepts for constraining their interfaces more strictly defines what valid uses of these algorithms are. These changes allow you to make refactors like:

// C++17 algorithm
cat find_kitten(const std::vector<cat>& cats) {
    return *std::find_if(cats.begin(), cats.end(),
        [](cat const& c) { return c.age == 0; });

// C++20 algorithm
cat find_kitten(std::span<cat> cats) {
    return *std::ranges::find(cats, 0, &cat::age);

2023 Annual C++ Developer Survey "Lite"


The annual global C++ developer survey is now open. As the name suggests, it's a one-pager:

2023 Annual C++ Developer Survey "Lite"

Please take 10 minutes or so to participate! A summary of the results, including aggregated highlights of common answers in the write-in responses, will be posted publicly here on isocpp.org and shared with the C++ standardization committee participants to help inform C++ evolution.

The survey closes in one week.

Thank you for participating and helping to inform our committee and community!

Broker -- Rainer Grimm

The Broker Pattern structures distributed software systems that interact with remote service invocations. It is responsible for coordinating the communication, its results, and exceptions.


by Rainer Grimm

From the article:

The Broker Pattern from the book  "Pattern-Oriented Software Architecture, Volume 1" helps solve many challenges of distributed systems, such as finding the appropriate service provider, communicating with them securely, using the right programming language, or dealing with errors. This will not go into the details. It should only provide you with a rough idea of the Broker Pattern. For further information, study the pattern in the book "Pattern-Oriented Software Architecture, Volume 1".

C++20 Lambda Extensions: Lambda Default Constructors -- Gajendra Gulgulia

GajendraGulgulia.pngIn this article, I cover Default constructuctible lambdas.

C++20 Lambda Extensions: Lambda Default Constructors

by Gajendra Gulgulia

From the article:

1. Default construction: Very short background

In C++ objects are default constructible if they satisfy certain conditions. The set of conditions vary and I’ll not go into all the details of what they are as it will be out of the scope of this article. Consider the Person class with default constructor in line 3. 

class Person{
         Person() = default;   //default constructor
         Person(std::uint32_t age, std::string name):
         age_{age}, name_{name}
         { /*empty body */ }

         std::string getName()  const { return name_;}
         std::uint32_t getAge() const { return age_; }
        void setAge(const std::uint32_t age) {age_ = age;}
        void setName(const std::string& name){name_ = name;}
       std::uint32_t age_{};
       std::string name_{};

TCP/IP Networking with Boost.Asio -- Richard Thomson

Utah C++ Programmers has released a new video:

TCP/IP Networking with Boost.Asio

by Richard Thomson

From the video description:

Boost.Asio is a cross-platform C++ library for network and low-level I/O programming that provides developers with a consistent asynchronous model using a modern C++ approach.

This month, Richard Thomson will continue our look at Boost.Asio with a look at TCP/IP networking. We'll look at how to implement an NNTP (Network News Transport Protocol) client using Boost.Asio. NNTP is a line-oriented protocol for reading usenet news articles. This will give us insight into all the typical issues involved in a TCP/IP networking application:

- How do we resolve a host name into an IP address?
- How do we establish a long-lived connection to an NNTP server?
- How do we handle the arbitrarily large amounts of data from an NNTP server that arrives asynchronously?
- How do we coordinate user input with NNTP I/O?
- How do we handle unexpected network errors?


C++23’s New Fold Algorithms -- Sy Brand

If you want to find out more about the std::ranges::fold_* algorithms in C++23, here's a new post for you.

C++23’s New Fold Algorithms

By Sy Brand

From the article:

C++20 added new versions of the standard library algorithms which take ranges as their first argument rather than iterator pairs, alongside other improvements. However, key algorithms like std::accumulate were not updated. This has been done in C++23, with the new std::ranges::fold_* family of algorithms.