std::expected - Monadic Extensions -- Bartlomiej Filipek

By Blog Staff | May 23, 2024 02:44 PM | Tags: None

The new std::expected feature from C++23 not only offers a robust error-handling mechanism but also introduces functional programming techniques like chaining operations with and_then, transforming results with transform, and managing errors using or_else and transform_error. This article explores these features, demonstrating how they can streamline your code by reducing redundant error checks while elegantly managing success and error states. Stay tuned as we dive into practical examples and see how these techniques are applied in real-world projects.

std::expected - Monadic Extensions

by Bartlomiej Filipek

From the article:

std::expected from C++23 not only serves as an error-handling mechanism but also introduces functional programming paradigms into the language. In this blog post, we’ll have a look at functional/monadic extensions of std::expected, which allow us to chain operations elegantly, handling errors at the same time. The techniques are very similar to std::optional extensions - see How to Use Monadic Operations for `std::optional` in C++23 - C++ Stories.

Here’s a brief overview of these functional capabilities:

and_then()
 

The and_then member function enables chaining operations that might produce a std::expected object. It’s invoked when the std::expected object holds a value and allows for seamless operation chaining without manual error checking after each step.

CppCon 2023 Back to Basics: Iterators in C++ -- Nicolai Josuttis

By Blog Staff | May 22, 2024 01:41 PM | Tags: None

Registration is now open for CppCon 2024! The conference starts on September 15 and will be held in person in Aurora, CO. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from last year's conference. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2024!

Back to Basics: Iterators in C++

by Nicolai Josuttis

Summary of the talk:

One key success factor of C++ was the introduction of the Standard Template Library (STL) bringing together containers/ranges and algorithms using iterators as glue API to iterate over elements of collections.

This talk will present the basics of the design of iterators, the various consequences, remarkable corner cases, and what this means when using ranges and views as introduced with C++20.

Adding State to the Update Notification Pattern, Part 5 -- Raymond Chen

By Blog Staff | May 20, 2024 02:27 PM | Tags: None

Managing stateful notifications is challenging when multiple requests arrive, and the goal is to only notify about the latest one. In the EditControl class, we use a counter to track the most recent request, updating it on the UI thread to ensure accurate ordering and prevent stale data from being processed. This approach works but is inefficient due to redundant calculations. Next time, we'll refine this strategy for greater efficiency.

Adding State to the Update Notification Pattern, Part 5 

by Raymond Chen

From the article:

We’ve been looking at the problem of a stateful but coalescing update notification, where multiple requests for work can arrive, and your only requirement is that you send a notification for the last one.

This time, we’ll apply the trick of using a counter to record who is doing the work on behalf of the most recent change. Here’s our first attempt:

 

class EditControl
{
    ⟦ ... existing class members ... ⟧

    unsigned m_latestId;
};

winrt::fire_and_forget
EditControl::TextChanged(std::string text)
{
    auto lifetime = get_strong();

    co_await winrt::resume_background();

    auto id = ++m_latestId;

    std::vector<std::string> matches;
    for (auto&& candidate : FindCandidates(text)) {
        if (candidate.Verify()) {
            matches.push_back(candidate.Text());
        }
    }

    co_await winrt::resume_foreground(Dispatcher());

    if (id != m_latestId) co_return;

    SetAutocomplete(matches);
}

CppCon 2023 Whitespace: A Humorous Short Talk -- Dan Curran

By Blog Staff | May 19, 2024 01:38 PM | Tags: None

Registration is now open for CppCon 2024! The conference starts on September 15 and will be held in person in Aurora, CO. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from last year's conference. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2024!

Lightning Talk: Whitespace: A Humorous Short Talk

by Dan Curran

Summary of the talk:

i want a holy war over whitespace. the most productive discussion.

2024-05 Mailing Available

By Administrator | May 18, 2024 11:14 AM | Tags: None

The 2024-05 mailing of new standards papers is now available.

CppCon 2023 C++23: An Overview of Almost All New and Updated Features -- Marc Gregoire

By Blog Staff | May 17, 2024 01:22 PM | Tags: None

Registration is now open for CppCon 2024! The conference starts on September 15 and will be held in person in Aurora, CO. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from last year's conference. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2024!

C++23: An Overview of Almost All New and Updated Features

by Marc Gregoire

Summary of the talk:

As I have done for previous C++ Standard versions, I will explore almost all new and updated C++ features that come with the C++23 standard. C++23 is not as big of an update as C++20 was, but it does contain numerous new and updated features to both the core language and the Standard Library. The goal of this session is not to discuss all new and changed features in detail, as that is not possible in a one-hour session. Instead, at the end of the session, you should have a high-level overview of everything that's new or changed in C++23, and it might even change how you are using existing features.

The session will touch on the following core language and Standard Library topics.

C++23 core language changes include explicit object parameters (deducing this), if consteval, multidimensional subscript operators, built-in decay copy support, ability to mark unreachable code, support for specifying platform-independent assumptions, named universal character escapes, and more.

C++23 Standard Library changes include string formatting improvements, formatting of entire ranges, standard named modules std and std.compat, new containers flat_map and flat_set, multidimensional span aka mdspan, a standard generator coroutine, monadic operations on optionals, working with stacktraces at run time, many changes to the ranges library, std::expected as an alternative to exceptions, and more.

Throughout the session, the slides will contain references to other CppCon sessions with more details on specific topics.

Noisy: The Class You Wrote a Hundred Times -- Vincent Zalzal

By Blog Staff | May 16, 2024 05:45 PM | Tags: None

You have probably written a class that prints a message in all its special member functions. And like me, you probably wrote it multiple times. I decided to write it well once and for all, and share it.

Noisy: The Class You Wrote a Hundred Times

by Vincent Zalzal

From the article:

Recently, I was writing some code involving structured bindings and I was unsure whether it would incur unintended copy or move operations. As usual, when I am in this situation, I open up Compiler Explorer and test it. For the nth time, I ended up coding a class like this one:

struct S { 
S() { std::cout << "ctor\n"; } 
~S() { std::cout << "dtor\n"; } 
// ... and so on with copy and move operations 
}

I don’t know how many times I wrote this class! I thought maybe it was time I write it well, once and for all, and then reuse it when I need it. And then, I thought that I am probably not the only one having written that class over and over again, am I? Maybe this could be useful to others.

The Performance Impact of C++'s `final` Keyword -- Benjamin Summerton

By Blog Staff | May 14, 2024 05:40 PM | Tags: None

If you're writing C++, there's a good reason (maybe...) as to why you are. And probably, that reason is performance. So often when reading about the language you'll find all sorts of "performance tips and tricks" or "do this instead because it's more efficient". Sometimes you get a good explanation as to why you should. But more often than not, you won't find any hard numbers to back up that claim. I recently found a peculiar one, the final keyword.

The Performance Impact of C++'s `final` Keyword

by Benjamin Summerton

From the article:

Multiple blog posts claim that it can improve performance(sorry for linking a Medium article). It almost seems like it's almost free, and for a very measly change. After reading you'll notice something interesting: no one posted any metrics. Zero. Nada. Zilch. It essentially is "just trust me bro." Claims of performance improvements aren't worth salt unless you have the numbers to back it up. You also need to be able to reproduce the results. I've been guilty of this in the past (see a PR for Godot I made).

Being a good little engineer with a high performance C++ pet project, I really wanted to validate this claim.

CppCon 2023 A Journey Into Non-Virtual Polymorphism in C++ -- Rudyard Merriam

By Blog Staff | May 13, 2024 01:17 PM | Tags: None

Registration is now open for CppCon 2024! The conference starts on September 15 and will be held in person in Aurora, CO. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from last year's conference. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2024!

CppCon 2023 A Journey Into Non-Virtual Polymorphism in C++

by Rudyard Merriam

Summary of the talk:

Join me on an introductory journey into polymorphism that doesn't use class inheritance and virtual functions. I'll share my amazement at how polymorphism permeates C++. Then we'll visit the long-used Curiously Recurring Template Pattern (CRTP) with its modernization using implicit this.

Do you like lambdas? So does the override pattern, which uses them to handle std::tuples and std::variants with std::apply and std::visit.

Want to walk through a container of disparate types invoking their functions? You'll see this and all the above in code examples galore.

Afterward, you'll be eager to learn more on your own!

Pure Virtual C++ 2024 Recordings Available

By TartanLlama | May 13, 2024 08:09 AM | Tags: community

The recordings for all Pure Virtual C++ 2024 sessions are now online. This includes the 5 main sessions plus over a dozen pre-conference videos.

Pure Virtual C++ 2024 Recordings Available

By Sy Brand

From the article:

All recordings for our Pure Virtual C++ 2024 conference are now available. Thanks to everyone who came along and hope to see you again next year! You can find the full playlist on YouTube.