The DConf Experience

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April 23rd, the deadline for DConf 2017 registrations, is just a few days away. Personally, I wasn’t sure if I’d be able to attend this year or not, but fortunately things worked out. While I’m looking forward to more great presentations this year, that’s not what keeps drawing me back (or makes me regret being unable to attend in 2014 and 2015).

The main draw for me is putting faces to all the GitHub and forum handles, then getting the opportunity to reconnect in person with those I’ve met at past conferences to talk about more than just the D programming language or the projects to which we all contribute.

I’m not the only one who feels that way. Walter Bright had this to say of DConf 2016:

Besides the technical content, I enjoyed the camaraderie of the conference. The pleasant walking and talking going between the Ibis hotel and the conference. The great food and conversations at the event. Chatting at the Ibis after hours.

If you’re staying at the Hotel Ibis Neukölln (which, unfortunately, is booked solid the week of the conference last I heard) and you’re an early riser, you’ll likely find Walter down in the lobby having First Breakfast and up for a good conversation.

Of course, the mingling isn’t necessarily confined to the conference hall or the hotel lobby. Conference goers sometimes share a room in order to save costs. That’s a great opportunity to learn something new about someone you might not otherwise have discovered, as GDC meister Iain Buclaw found out at DConf 2013 when he and Manu Evans were roomies for a few days:

I recall that I had gotten some microwavable food from the nearby groceries ahead of his arrival — “I didn’t know what you would like, or if you had allergies, so I went with the safe option and only got Vegan foods”. It was a pleasant surprise to discover we have a diet in common also.

At that edition, Iain, Manu and Brad Roberts were shuttled to and from the conference by Walter in his rental car. Carpooling has been a common part of the Stateside DConfs. At the venue in Berlin, there’s no need for it. The semi-official hotel is in walking distance and there’s a subway stop nearby for those who are further off. And, as Steven Schveighoffer can attest, rental bicycles are always an option.

I remember last year, Joseph Wakeling, Andrew Edwards and his son, and myself went for a great bike tour of Berlin given by native David Eckardt of Sociomantic. This included the experience of dragging our rented bikes on the subway, and getting turned away by police in riot gear when we had inadvertently tried to go somewhere that political demonstrations were happening. Highly recommended for anyone, especially if David is gracious enough to do the tour again! We randomly met Ethan Watson riding a rented bike along the way too 🙂

Speaking of Ethan, it appears there’s a good reason that he was riding his bike alone and in the wrong direction.

My first BeerConf was in 2016, located in the rather interesting city of Berlin. Every evening, we would gather and drink large amounts of very cheap beer. This would also coincide with some rather enjoyable shenanigans, be they in-depth conversations; pub crawls; more in-depth conversations; convenience store crawls (where the beer is even cheaper); even more in-depth conversations; and a remarkable lack of late night food.

Hours during the day were passed away at a parallel conference that I kinda stumbled in to, DConf. Interestingly, this was stocked with the same characters that I socialised with during BeerConf. Maybe I was drunk then. Maybe I’m drunk now. Did I present a talk there? I think I did, although I can only assume the talk did not have anything to do with beer.

I’ve found out recently that I’m dual-booked for BeerConf 2017 as well as presenting again at DConf. Since attending these events can only be achieved through a submission process my deduction is that I had a thoroughly good time meeting all these people and socialising them, as well as sharing knowledge and technical expertise, and decided I must do it again. Either that, or someone else signed me up. Don’t tell me which option is the truth, I’ll work it out.

Yes, the beer is a big part of it, too. This blog was born at the small bar in the lobby of the Ibis, over a couple of cold ones and the background cacophony of D programmer talk. Who could say what new D initiatives will spawn from the fermented grains this year?

But let’s not forget the presentations. While they’ll be livestreamed and those who don’t attend can watch them on YouTube in perpetuity, the social aspect lends a flavor to them that the videos just can’t. Andrew Edwards is a fan of one speaker in particular.

I’m always fascinated by Don Clugston’s talks. The most memorable is DConf 2013, during which he stated that, “The language made minor steps… We got here like miners following a vein of gold, not by an original master plan,” in his explanation of how D arrived at its powerful metaprogramming capabilities.

Where else can you hear “wonks” recounting their first hand experiences of what makes D “berry, berry good” for them? It is just a great experience talking and exchanging ideas with some of the greatest minds in the D community.

And there’s no substitute for being in the room when something unexpected happens, as it did during Stefan Koch’s lightning talk at DConf 2016, when he wanted to do a bit of live coding on stage.

There was no DMD on the computer 🙂 That surprised me.

Whether your interest is social, technical, alcohological, or otherwise, DConf is just a fun place to be. If you have the time and the means to attend, you’re  warmly invited to make your own DConf memories. Do yourself a favor and register before the window closes. If you can’t make it, be sure to follow the livestream (pay attention to the Announce forum for details) or pull up #D on to ask questions of the presenters. But we really hope to see you there!

I’ll leave you to consider Andrei Alexandrescu’s take on DConf, which concisely sums up the impact the conference has on many who attend:

To me, DConf has already become the anchoring event that has me inspired and motivated for the whole year. We are a unique programming language community in that we’re entirely decentralized geographically. Even the leadership is spread all over across the two US coasts, Western Europe, Eastern Europe, and Asia. Therefore, the event that brings us all together is powerful – an annual systole of the live, beating heart of a great community.

We don’t lack a good program with strong talks, but to me the best moments are found in the interstices – the communal meals, the long discussions with Walter and others in the hallway, the late nights in the hotel lobby. All of these are much needed accelerated versions of online exchanges.

I’m very much looking forward to this year’s edition. In addition to the usual suspects, we’ll have a strong showing of work done by our graduate scholarship recipients.

Thanks to Walter, Iain, Steven, Ethan, Andrew, Stefan and Andrei for sharing their anecdotes and thoughts.

Ruminations on D: An Interview with Walter Bright

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Joakim is the resident interviewer for the D Blog. He has also interviewed members of the D community for This Week in D and is responsible for the Android port of LDC.

d6Walter Bright is the creator and first implementer of the D programming language. He was an early developer of C++ compilers starting from the mid-’80s, including the first C++ compiler to translate source code directly to object code without using C as an intermediate, and has written compilers for ABEL, C, Java, and Javascript. He believes he is the only person to have written a full C++98 compiler by himself. Empire, one of the first computer strategy games, was written by Walter at Caltech. Before getting into computer programming full-time, Walter worked for Boeing from 1979-1982 on the 757’s flight controls, particularly the stabilizer trim gearbox and system and the elevators.

Joakim: D appears to be picking up speed. The fourth straight DConf took place earlier this year, Wired wrote a nice article a couple years ago, Gartner ranked it in the top 20 languages soon afterwards, and downloads of the reference compiler, DMD, average 1200 per day in recent years. Talk about the current popularity and status of the language and what you’re doing to take it to the next level.

Walter: I don’t worry too much about that. I spend my efforts making D the best language possible, and let the metrics take care of themselves. It’s like being a CEO; he shouldn’t be sweating the stock price, he should be working on making money for the company, then the stock price will take care of itself.

There’s always a stack of things to do, more or less with the most important one on the top, and I pop the top off and work on it, mostly the one with the maximum benefit/cost ratio. The ordering in the stack changes all the time. If an item has others strongly interested in working on it, I defer to them.

I get the jobs that nobody else wants to do. 🙂 Regression fixes for complex problems is a big one. It’s much more fun designing new stuff than maintenance on the existing stuff, dealing with technical debt, etc.

Joakim: In the last year, @nogc and interfacing with C++ have been at the top of your stack. Why? You always used to say that interfacing more with C++ would be too much work.

Walter: It became clear that the garbage collector wasn’t needed to be embedded in most things, that memory allocation could be decided separately from the algorithm. Letting the user decide seemed like a great way forward.

As for C++, I figured out a way to support it that avoided the problems I thought were impractical to deal with. I did a talk about it PDF slides here– and a Rust user wrote up a partial transcript.

Since that talk, I’ve come up with a solution for exceptions. C++ can throw/catch exceptions of any type. But few people do anything other than throw/catch a reference to a class, like std::exception. All D needed to do was allow throw/catch of a class marked with the extern (C++) attribute. Throw/catch of other types remains unsupported, and most likely will remain unsupported.

In order to make that work, the custom exception handling code in the code generation and the library had to change to work with the DWARF exception handling mechanism. That turned out to be a fair amount of work, as it is rather under-documented. But it’s pretty simple for the user.

Joakim: What do you plan on working on in D for the rest of the year? Work on @nogc and C++ support seems to be ongoing and you’ve tried to increase the use of ranges in the standard library for some time now. Anything else? What is the status of those efforts?

Walter: Those are still high-priority and ongoing efforts. But also we’re flexible; if a major opportunity comes up that needs us to push in a different direction, we’ll adapt. The pervasive use of ranges is advancing rapidly, I’ve been very pleased with the results.

The current focus is on improving memory safety. It’s become more and more important to have verifiable memory safety in a programming language, as the expenses involved when unsafe code is exploited in order to install malware become greater and greater. D has always supported memory safety, but recently we’ve embarked on a much more comprehensive review of memory safety in the core language and are making changes to close the gaps.

Joakim: How much time do you spend on D and what is your daily routine?

Walter: I work full time on D. I probably spend half my time working on the language, and the other half helping others with it, discussing things, doing interviews (!), writing articles, doing conferences, etc.

Joakim: You were 42 when you started working on D and I guess it is the first language you designed? Talk about why you started working on it so late–you were probably older then than most of the D contributors now–and what insights your experience gave you that your younger self or other young contributors may not have.

Walter: ABEL is the first language I designed, and was a solid success for Data I/O. It’s obsolete now, because the electronic devices it was aimed at are now obsolete, but it had a great run for 10 years or so.

Having been writing compilers my whole career, doing tech support for them, and following the various changes in the languages inevitably gave me much insight on what worked and what didn’t. Probably the biggest thing is that simpler is better. But making something simple is actually quite difficult. Anybody can (and does) design a complex solution, but few can see through the complexity to find the underlying simplicity.

Many successful languages were designed by older engineers.

Joakim: Please give some examples of such simplicity and how you were able to find it.

Walter: We nailed it with arrays (Jan Knepper’s idea), the basic template design, compile-time function execution (CTFE), and static if. I have no idea what the thought process is in any repeatable manner. If anything, it’s simply a dogged sense that there’s got to be a better way. It took me years to suddenly realize that a template function is nothing more than a function with two sets of parameters –compile time and run time–and then everything just fell into place.

I was more or less blinded by the complexity of templates such that I had simply missed what they fundamentally were. There was also a bit of the “gee, templates are hard” that predisposes one to believe they actually are hard, and then confirmation bias sets in.

I once attended a Scott Meyers presentation on type lists. He took an hour to explain it, with slide after slide of complexity. I had the thought that if it was an array of ints, his presentation would be 2 minutes long. I realized that an array of types should be equally straightforward.

With CTFE, we just went straight in the front door from asking the question “why can’t we execute this function at compile time, just like constant folding?” I did the initial one just by extending the constant folding logic. Don Clugston took it much further, but at its heart it’s still a modified dwarf. Stefan Koch is currently working on making a real interpreter out of it.

Joakim: Why do you think there hasn’t been a killer app for D yet? For example, Ruby was kind of an obscure language for a dozen years till Rails propelled it into the spotlight.

Walter: I suspect the age of the killer app is behind us. There is so much software existing and being written, for every imaginable purpose, that it’s hard to believe there will even be another killer app of any sort. Of course, predictions are notoriously unreliable.

Joakim: D has a unique approach in the compiled languages market, being mostly community-developed without a major corporate sponsor. C++ had Bell Labs, Rust has Mozilla, Go has Google; all have full-time paid devs on the language, even if they also take open-source contributions. Do you think this is a problem and is D being left behind?

Walter: We recently started a D foundation which will make it a lot easier for corporations to sponsor D.

Joakim: Do you make money off D? I know you’ve contracted with Facebook to write a C++ linter, Flint, and preprocessor, Warp, and that you work with Sociomantic and other companies using D.

Walter: I do some paid consulting work for D, but am careful not to take on so much that it interferes with working on D itself.

Joakim: Do you write much code in D outside of the standard library? If so, talk about recent stuff you’ve written and how the experience has been, plus a bit about using some of the new features.

Walter: D consumes so much of my efforts, there’s not much time to write other D apps other than smallish utilities. Currently, of course, the D compiler front end itself is now in D. But it’s been translated from C++, so isn’t idiomatic D.

Joakim: OK, so I guess Warp is the largest program you’ve written in D lately, about 10 klocs. Can you talk about the experience of actually coding that in D, as opposed to C/C++? What stood out for you?

Walter: What stood out is the speed with which it went together, and the remarkably small number of bugs that surfaced in it after it was released. I credit the extensive use of unit tests for the latter.

Having written another preprocessor before certainly helped, and it would be hard to tease that out as a separate effect. But I still believe that unit testing made the difference, because the way the preprocessor worked was very different from the one I’d done before.

What stood out with D was the ease of changing the data structures to try different ways, compared with doing this in other languages.

Joakim: When you think back to your vision for D as you were starting out in 1999, does it at all resemble that today? Anything big missing that you wanted back then?

Walter: D is far more advanced than what I thought of 15 years ago. Programming language ideas have certainly advanced since then, and D along with it.

D originally wasn’t going to have templates at all, based on my earlier experience with them. But finding a simple way to do them changed everything – even to the point where well over half of a modern D program is templates!

The idea of ranges slowly evolved over time, we’re still learning how to do it right.

bit as a basic type was unworkable. complex as a basic type turned out to be pointless (it works better as a library type). Auto-decoding of UTF-8 to code points turned out not nearly as useful as expected.

Transitive const was a leap of faith, and is consistently overlooked by other languages looking to adopt D features. I have a lot of faith in transitive const, and it is already paying off in making it possible to have pure functions, a key feature for modern programming.

The Why and Wherefore of the New D Improvement Proposal Process

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When a programmer sees fellow programmers contributing code to open source projects, it is unlikely that the question of why will ever come to mind in terms of motive. Regarding technical merit or usefulness, sure. But motive? Coders who are inclined to contribute bug fixes, new features, build systems, or other resources to open source projects do so for a variety of reasons, most of which other programmers will intuitively understand. But when a programmer volunteers to take over what is solely an administrative process for an open source project, that’s a different story altogether.

Code contributions are usually one-off affairs. They require a time investment up front, but once the PR or patch is merged, that’s often the end of it. Managing an administrative process, on the other hand, is an ongoing commitment. Time that could be spent coding is instead spent doing the proverbial paperwork. And the benefit to the volunteer may not always be clear. Implementing a ray tracer and going bungee jumping are things you might do for the hell of it. Administrative tasks? Not so much.

The most recent post on this blog highlighted two non-coding initiatives which were kicked off by members of the D community. One of them is a new process for handling D Improvement Proposals, or DIPs. This was the work of Mihails Strasuns. Not only did he put together a new process, he also volunteered to manage it. What on earth was he thinking?

There isn’t anything special or unique about DIPs. Most programming languages that rely heavily on community input get something similar at some point. Once a language matures, changing even small bits of it becomes challenging and needs careful consideration. All of the relevant information has to be published somewhere.

The previous DIP process looked like a collection of articles on a community wiki. It seemed to work pretty well initially, when the DIP count was low enough, but with the number of improvement proposals reaching 100 and most of them still remaining in “draft” status, scalability issues became noticeable.

He highlights three issues specifically. First up is quality control.

There was no quality control for submitted proposals and, as a result, submissions were often lacking detailed information about language impact.

With the DIPs being Wiki-based, anyone with a D Wiki account could add a page for a new DIP, but there was no one designated to ensure that new DIPs met any sort of standard. This resulted in quality ranging from a detailed treatise that covered all the bases, to something that looked like notes on a cocktail napkin. Some remain in draft status, having never been finalized by their authors.

Another issue is the lack of response from the leadership.

It was very rare to get a formal response from Andrei or Walter regarding a DIP, partially because proper reviewing of incomplete proposals was demanding too much time.

Walter and Andrei already have their hands full. The last thing they need is to spend time reviewing a DIP that isn’t ready for review. A DIP should be ready for their consideration before it is brought to their attention and not require them to ask for information that should already be there. Without a designated arbiter to decide when a DIP is complete, how are they to know? The author of a DIP may believe it ready, but all too often will be wrong.

Finally, there is the issue of maintaining the list of DIPs.

Abandoned or rejected proposals often were not marked as such because editing the list was purely a community effort.

With no one person responsible for maintaining the list, it was updated only when someone in the community noticed an update was needed and was willing to make the appropriate edits. The result was that there were only a small number of people who ever touched it.

So the solution Mihails came up with to address all of these problems, which he says is similar to that used with other modern programming languages, is described in the README of the new github project he set up to replace the Wiki. It outlines the procedure, including how to submit a DIP and how to get it approved, gives advice on how to write a great DIP, and even outlines the responsibilities of the new DIP manager. Which, for now, is him.

And that brings us back to the topic of the first couple of paragraphs. We now know the problems he saw with the process and how he decided to improve it, but we still don’t know why. So, why, Mihails?

There is, of course, a personal reason which caused me to step up with this process proposal. In a way, this is an attempt to solve a conflict of interest that arises from being employed by one of the largest D commercial users while being actively engaged in the language on my own. I want for the language to change and improve, but, at the same time, I have to ensure any such changes don’t cause too much disruption to our systems at work.

That commercial user of which he speaks is Sociomantic, hosts of the excellent DConf 2016 in Berlin and maintainers of the ocean and makd projects they opened up for the D community.

Having a formalized process for language changes helps a lot in that regard. It means there is a single information feed to follow if one doesn’t want to miss anything of major impact. It’s much more concise than a newsgroup or mailing list. And volunteering to handle the DIP bureaucracy allows me to make timely suggestions for better ways to handle any changes so that they don’t cause too much trouble to existing code.

The DIP process arose organically to fill a void. Its was, perhaps, inevitable that its ad hoc existence take another step in its evolution. It was just waiting for the right person with the right ideas and the willingness to make it happen. That person turned out to be Mihails Strasuns. The D communnity will be better off thanks to his efforts.

The DLang Vision and Improvement Process

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The evolution of D has been a process of steady, if not always speedy, improvement. In the early days, Walter was the only person working on the language, the reference compiler, and the standard library, though he did accept contributions. Today, numerous people contribute to or maintain a piece of every aspect of D’s development. Semi-formal processes exist where none did before. Things have come a long way.

As with anything in life, those who come later are unaware of the improvements that came before. If you’ve just stepped off the boat into D Land, you don’t remember the days before core D development moved to github, or the time before the first release of Visual D, the D plugin for Visual Studio developed and maintained by Rainer Schuetze. All you’re going to see is that your pet Pull Request hasn’t yet been merged, or that Visual D doesn’t allow you to do all of the things that the core of Visual Studio allows. You’ll rightly head over to the forums to complain about the PR merge process, or request a new feature for Visual D (or gripe about its absence).

And so the story goes, ad infinitum. Along the way, the community loses some members who once found promise in the language, but become frustrated because their pet peeves have not been addressed. And herein lies the point of this post.

The D Programming Language is a community driven language. As such, there is no formal process for creating opportunities to fix and improve the areas that need fixing and improving. Walter has his head down in compiler code and often barely has time to come up for air. Andrei is stretched thin in the additions he has planned for Phobos, the work he does on behalf of the D Foundation, and his numerous other commitments. It’s up to the community to get things moving on other fronts.

Most often, improvements come at the instigation of one highly motivated individual, who either gets busy with the rolling up of sleeves or keeps pushing until someone better positioned takes up the challenge. Still others want to contribute, but aren’t sure where to begin. One place is the documentation, as described the last time this blog touched on this theme. For other areas, the place to look is the D Vision Document.

Andrei started the Vision Document as a means to let the community know the direction in which he and Walter expect the language to go, with plans to release an updated document biannually. Each document lists progress that has been made in the preceding six months and the goals for the coming six. The first document focused on goals the D leadership will personally enable or make happenThe latest document, which was put up for feedback recently in the forums, includes additional goals the leadership strongly believe are important for the success of the D language. This new addition is the result of an initiative by community member Robert Schadek.

Robert took the simple step of creating a Wiki page to collate the wishlist items that Walter and Andrei mention in the forum now and again. These are things they would like to see completed, but have no time to make happen themselves. Andrei merged these items into the Vision Document so that there is only one document to maintain and one source for the information. This is a perfect example of a low-barrier community contribution that has led to an overall improvement (though Robert is no stranger to higher-barrier contributions) and shows how there are ways other than submitting Pull Requests to improve the D Programming Language experience.

A higher-level means of helping to improve the language is through D Improvement Proposals. A DIP is a formal proposal to make changes or additions to the language. The author of the DIP need not be the implementer. For some time, these have primarily been loosely maintained in an informal process at the D Wiki. Recently, Mihails Strasuns decided the process needed better management, so he created a github repository for DIPs as part of a new process to address some shortcomings of the old system. Then he made a forum announcement about it, including the news that he is, for now, volunteering his services as the new DIP manager.

So, to recap, if you are itching to contribute to D in some way that you know will have an impact, the latest Vision Document is the place to go for inspiration. As I write, that’s the 2016H2 document. If you have an idea for a new feature or improvement to the language, creating a DIP is the way to go (a future post here will say more about the DIP process). There are numerous other areas where contributions are welcome, like fixing or reporting bugs, reviewing PRs, and taking the initiative to contribute to the D process like Robert and Mihails have done.

If you don’t have the time, motivation, or inclination to contribute, that’s fine, too. Just keep in mind when you come to the forums to vent about one frustration or another (and please, feel free to do so) that much of what exists in the D ecosystem today, along with nearly every improvement that will come for the foreseeable future, is the result of someone in the community expending their own time and effort to make it so, usually with no financial incentive (the exception being bug bounties). Please let that knowledge color your perspective and your expectations. If you can’t, or won’t, work to resolve shortcomings in the language, the processes, or the ecosystem yourself, your goal in bringing them to the community should be to motivate someone else to do so. Not only will that increase the odds of fixing your issues, it will help all D users inch closer to the ultimate D Nirvana.

The D Website and You

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For those who have been around the D community for a long time, it’s all too easy to look at the website we have today and think how much better it is than anything we’ve had in the past. It’s miles ahead. Unfortunately, that perspective doesn’t lend itself well to recognizing actual problems that newcomers might face when visiting the site for the first time. Their point of reference is quite often the current website of another language, making their perspective on what does and doesn’t work very different.

It goes without saying that D is primarily a community-driven language. It doesn’t have a large company with a dedicated team of paid workers pushing its development. The website is one of the areas where this has a major impact. Its quality is almost entirely dependent on community contributions. Quite often, it’s recent additions to the community, those who have fresh eyes, who step up and push for improvements to the site. Several have been implemented in the past few weeks, thanks to community members who saw a void and took the initiative to get it filled.

André Stein put together an interactive tour of the language and set it up online. Now, that is part of the official site as, available from the menu bar at the top of most pages by clicking on Learn. This is a tremendous improvement over what existed before, when users had to browse through different link categories to find the resources they needed, none of which were such a quick introduction to the language.

Sebastian Wilzbach has initiated a number of additions and improvements to the website in the short time he has been active in the community. One such addition is a page listing a number of organizations currently using D. Before, this information was only available on the Wiki. Now, it’s a first-class citizen of

Sebastian also put forth a suggestion for a major change in how the website is deployed. Previously, changes to the site had to be manually deployed, a process which caused a delay between when the changes were made and when they became visible. This led to a situation where news on the front page could become horribly outdated. Sebastian’s suggestion was approved and now updates to the site are deployed automatically when they are merged.

Another user, Ozan Nurettin Süel, was looking for the D Foundation website and coming up empty. A post about it in the forum led to a new page being added to the site. Anyone who wants to learn about the Foundation and, once memberships are open, how to join now has somewhere to go for that information under the umbrella.

As Andrei said in his DConf keynote this year, the first five minutes become the next five years. The website plays a major role in that first five minutes. It’s up to us as a community to ensure that it meets the needs of potential new users instead of getting in their way. Small changes can often have a big impact. Whether you are an old timer or a newcomer, if you see something that is missing from the site, or have an idea for how to improve it, please let us know. If you notice broken links, incorrect text, or other such issues, please report them. Only then can evolve to fully meet the needs of those coming to it for the first time.