Programming in D: Tutorial and Reference
133 comments
·April 25, 2025usrbinenv
realharo
Dart is much worse than TypeScript. The over-reliance on codegen for the most simple things (e.g. https://pub.dev/packages/freezed#primary-constructors), the lack of expressiveness of the type system (it only got sum types very recently), and a lot of other little annoyances are ever present when having to write Dart.
old-gregg
Languages do not matter as much as you think. Ecosystems are everything. Twice in my life I started companies (the first one took all my life savings) and in both cases the right call was what you called an "inferior language".
I actually liked D very much, and WB had been a personal hero of mine when I was in college. But I am not betting my career on an ecosystem built around by a single brilliant guy. For high-stakes projects, a wise decision is building on a platform with several deep-pocketed backers.
And for toy/personal projects... do you even need a language anymore? Just ask your favorite LLM to generate you an executable which does what you want (partially joking here).
WalterBright
D's ImportC feature makes it super easy to access C libraries from D code. That means D fits right in with a C ecosystem, as it's no longer necessary to attempt to translate the .h files into D.
It's not perfect, as some people cannot resist using the C preprocessor for some bizarre constructions.
I used to write those bizarre things myself in C, and was proud of my work. But one day I decided to remove them all, and the code was better.
giancarlostoro
One area where Go, C# and Rust beat D is packages in a few different ways.
For C# Microsoft eventually embraced NuGet their package manager, and used it to put core packages that don't need to be fully available OOTB but can then benefit from frequent updates on a per project basis as opposed to updating the entire language runtime.
For Go it was the out of the box packages, like if I want to make a website, I can pull in net/http and their templating packages that come out of the box with Go, maybe a reasonably simple core maintainer package or packages that go into Dub would be a strong selling point. Right now Vibe.d is the only option for web dev, but there's no reason a much simpler web server couldn't exist.
For Rust, I just really love Cargo, I think its one of the nicest package managers I've ever used.
The other thing that would really help D is if something significant is built around D, whether it be a framework (like what Rails did for Ruby) or some major application that needs D to function at its core and is used by many, this could be a groundbreaking modern IDE, or anything really, a database that uses the best bits and pieces of D to scale, or even a really rich cross-platform GUI stack (my kingdom for std.gui to be a thing in D, and reasonably exhaustive).
I wish I had unlimited time and money, I would invest it in D. Alas, I'm not a language maintainer, just a guy who loves really good tools.
kev009
It seems like the parent was trying to paint a situation of you being a bottleneck to success. It seems a bit Schrödinger's BFDL though.. is Linus a bottleneck to the most used server operating system? Did Guido hold back Python? The existence of the GDC and LDC compilers torpedoes toolchain concerns.. I'd be more worried about Java or Golang suffering from some eventual corporate buffoonery.
To the parent's point of startups, betting the farm on something like a particular language out of some sense of superiority might mean you are not focusing on the right problems. But if the founders happen to know a less widely used tool it doesn't seem inappropriate either. The type of employee that can drive a startup or a big tech project forward is not going to be thwarted by a language, and they might find something new to learn fun.
zerr
Any plans to implement Swift like C++ interop?
ofrzeta
It would be great if D supported something like OpenAPI generator https://github.com/OpenAPITools/openapi-generator
Maybe it exists and I am just ignorant but it doesn't seem to be in the list of supported languages.
pjmlp
I belive asking the favorite LLM to generate an executable will be the future, just like high level languages drove Assembly development into a niche.
Yes it isn't here today, just like it took several decades for optimizing compiler backends to do a very good job.
In fact one of the reasons why Matt Goldbolt created Compiler Explorer was to have a way to settle arguments he was having in the games industry.
Koshkin
> LLM to generate an executable
... and the job of a programmer will be to explain, in as precise terms as possible, what they need the executable to do. (Reminds me of the idea of programming based on a natural language.)
pjmlp
What pains me in Python adoption, beyond its use as Perl replacement, is that we have so much better dynamic languages with advanced JIT implementations, but have to reach out writing extensions in native languages instead.
At least Python as DSL for GPU JIT compilers is a thing now.
Yes, I know about PyPy in the corner looking for attention.
creata
> we have so much better dynamic languages with advanced JIT implementations
What are some of these better languages that you're referring to? (The usual dynamic language JITs I hear people praise are LuaJIT and Chez. And V8. And the JVM?)
pjmlp
Smalltalk, Self, whose research lead to Hotspot and V8, Common Lisp.
And the usual, in Python everything is dynamic, well it is even more so in an image based live coding environment, where any break into the debugger, with code changes and resume execution can come back to a complete different world.
Additionally there are features like Smalltalk become: message, where two objects can change places everywhere they are used in the image, and current execution.
esafak
I'd suggest F#, Clojure, Elixir, Scala, and TS, if that counts.
__s
Even Ruby has JIT now
chenzhekl
The superior languages on your list just reflect your personal preferences. There are not perfect languages, just appropriate languages for given application.
ofrzeta
It's quite subjective what you consider to be better. Is Ruby better than Python? Maybe so, but Ruby only ever had one killer app that is Rails while Python has a vast ecosystem. Is Crystal better than Go? Maybe so, but Go ist just so much more mature (plus the ecosystem argument).
nilslindemann
> Python preferred over Ruby
Python's syntax is closer to written human language, and it uses more obvious words.
> TypeScript preferred over Dart or even JavaScript
Typescript is a strict superset of JavaScript.
> Go is preferred over Crystal and D
Go is backed by a big Corp
bnolsen
Regarding ruby and python I thought the 2 were in the same league, esp compared to perl. Over 20 years ago I evaluated both and went ruby because of the more consistent api and of course pythons forced whitespace is an easy tie breaker against it. At this point I'm not to pleased that many younger programmers that python as some sort of default and tend to end up writing far too fancy code in it when it ends up being the wrong tool.
Shorel
Performance matters (as long as most other things are the same).
Python won over Ruby because of performance. Ruby is easily the slowest of all mainstream languages.
WalterBright
Currently I'm working on adding an AArch64 code generator to the venerable dmd D compiler. It's fun as it's completely differernt from the X86_64. In some ways very clever and in some ways completely wacky.
zascrash
D deserves more recognition. It's a cool language under the radar for too long. I wish a major corporation backed it. I had a great time learning D. Also I admire Walter Bright If I could achieve even a fraction of his productivity, that would be awesome.
creata
Sincere question, not meant to be a shallow dismissal: Where is D a better choice than C++? In what aspects is it enough of an improvement over C++ to justify using a niche language?
Neku42
Programming in D after C++ is like the opposite of death by 1000 cuts - its just a constant stream of finding nice little things that simplify your life or avoid footguns. You become accustomed to all the niceties very fast and its hard to justify going back haha.
D is by no means perfect (and over the years it has accumulated lots of warts) but if you know what you are doing it enables amazing productivity and almost never gets in your way. If you have an idea about solving a problem in a particular way there's almost always a path available to do just that without running into "computer says no" situations (stares at Go).
acehreli
D is technically better than C++ in most features. (It has always lead C++. For example, among about 100 new feauters that C++11 brought, only 2 were not already in D. No C++ designer will ever admit this fact.)
D is safer and more productive. It's a joy to write in D because most of the time it feels like whatever you think, you code. This is unlike C++ where you fight the language all the time. C++ is not a productive programming language. I say this with experience: I coded in C++ as an "expert" for many many years, including these last couple of years. It's not fun to write in C++, which translates to another kind of loss of productivity.
C++ is a burden and liability for companies but no CTO will be blamed for chosing it because it's popular. I can list so many popular things and persons that worth nothing but I will refrain from getting political.
Yes, on paper, there are way more C++ programmers out there than D programmers. But I interview these C++ programmers occasionally. Most of them don't even have an inkling that they don't know C++ at all.
How about engineering with C++? That is such a difficult task. I went over header file hygiene with a colleague a couple of months ago. The number of points that you should pay attention to is mind boggling: Don't #include unnecessarily, do forward declare as much as possible (but what can be forward declared is hard to understand even for experienced programmers), #include your own API header first to prove that it's complete (and good luck!), don't forget header guards, don't reuse header guards, etc. etc. This is just efficient header file usage! We haven't started coding yet!
My friends, the emperor doesn't have clothes. C++ simply is not a tool that is designed well. People who choose it do so because they have to or they are masochists. (True story: I asked a relatively young Google meetup presenter once why he was using C++ instead of a modern language and he said "because it is hard".) C++ separates the elite from the masses; I used to strive to be a C++ elite; I am not interested a bit anymore; I want to write useful programs with D; and I do.
D is niche only because humans are populists. We are not encouraged to use tools (or products) that are designed better. We follow popular leaders. It takes one some time to find his or her own voice to reject bad products and use only good ones. I am extremely lucky to work for a company that allows me to use D to write useful products.
I still take the same joy from programming that I did when I first learned it.
Then there is the human aspect of it: I want to be associated with real people isntead of snobby elites. (Remember how C++ was marketed at around 2000? "Yes, C++ is hard but it was never meant to be for normal programmers anyway." Ha ha ha! I am old enough now to reject that mentality. Bad design is bad design my friends; you can't defend it by blaming the user for not being elite.)
I can go on and on...
Now it's my turn to ask: Why would anyone choose C++ for their projects despite the production costs that it brings? None of your programmers really know it; they introduce hidden liabilities in the projects, their source code become non-refactorable monsters. Why waste that money on C++ when you can produce products easily. Products that just work...
creata
> Why would anyone choose C++ for their projects despite the production costs that it brings?
Familiarity, and all the libraries and tools available for C++. I see that D has a section on C++ interop,[0] but it looks about as painful as FFI usually is, and even more painful given how template-heavy C++ code tends to be.
(Completely unrelated: I can't mention FFI without also mentioning how amazing LuaJIT's C FFI is. The developer(s) really nailed it.)
monkeyelite
I actually don’t think C++98 was that bad or complex. Yes nobody knew how to use it and wrote Java instead, but I think the hate comes from having code spanning so many different features and idioms that also require a compiler expert to understand.
shoozza
Slightly off topic: Is D a good language for creating tiny windows or Linux executables? There is an upcoming game jam (4mb jam 2025) which gives extra points for game submissions <= 8KB. With c you can fit a window with graphics update in an executable of less than 900 bytes[0]. Granted it's using crinkler for linking which does some compression.
0: https://gist.github.com/ske2004/336d8cce8cd9db59d61ceb13c1ed...
monkeyelite
Yes. Just use the “better C” mode
mariusor
... which is not D any more though.
WhereIsTheTruth
It's like saying "C is no longer C if you don't link with libc", it just is not true at all, and honestly, a pretty stupid thing to say
monkeyelite
What essential features are missing for you?
Daunk
I feel like D is such an underrated language.
WalterBright
We're not good at marketing! But we're very good at language ergonomics.
jadbox
Just to add, I learned D in a day and finished most of project euler without needing to look up the manual. D is more "python" than python in that it makes coding very.
IMHO, Zig is the closest thing to being D-esk (like with comptime), but it's still not a mainstream option yet.
jadbox
* makes coding very straight forward. Most of the time I find what I needed in the language just using intuition.
kingbob000
Love D! I used it a bit in college when it was required for a programming language class. It's hard to justify using it nowadays though.
bsdooby
Utah Valley University? Or Romania, or Turkey? And why is D's usage hard to justify (because of Rust and/or contemporary C++)?
acehreli
Mike Shah has been using D for teaching software engineering at Northeastern University and Yale. Here is his DLang playlist: https://www.youtube.com/playlist?list=PLvv0ScY6vfd9Fso-3cB4C...
MikeShah
We have also been using D for computer graphics and game programming as of this year! :D
kingbob000
Yes, UVU. And also yes. If I find myself needing something low-level and performant, I have a hard time justifying the ramp-up time required to use D since there is a near zero chance I would use it in my current or future employment. While that isn't always how I decide what technologies to use in my personal time, it definitely is a factor that tips the scales towards a more mainstream language
croemer
Anything compiled with LDC2 >=1.29 (3y old) will immediately crash/segfault on macOS >=15.4
A fix is on master/beta but will still take some time to be released.
acehreli
Author here... AMA.
usrbinenv
I recently read almost the whole book in a week or so. It's excellent and I feel like I can write in D pretty well after reading it. Too bad that I most likely won't be writing in D, but, at least, I'm confident I can come back to it anytime and be up to speed if I ever need to. This book should be the goto for anyone who wishes to quickly learn the language.
bachmeier
Been a heavy user of the language since 2013. This book was very helpful at the time. I don't think it was a book at that time, though, more a lengthy collection of notes as I recall.
acehreli
Exactly. It really was a happy accident. I talked about it here: https://dlang.org/blog/2016/06/29/programming-in-d-a-happy-a...
pmags
It's been about 10 years since I last dipped my toes in the D waters.
At the time (v 2.067) I stumbled across some surprisingly bad warts in the standard library that prevented me from using it for my intended purposes which writing software tools for bioinformatics.
As other posters have noted, language elegance is secondary to the ecosystem when you want to get things done.
For anyone who has been using D for an extended period, has the D ecosystem improved / expanded considerably in the last 5-10 years?
Alifatisk
The Youtube channel Tsoding did a great overview of the D language, overall, he liked it!
nerdralph
I tried D several years ago, and liked the language. I didn't stick with it because of the lack of libraries compared to perl, python, C++, etc.
jpecar
Is D runtime still crashing when host has more than 128 cpu cores? I learned this the hard way ...
alphaglosined
Are you talking about "Issue 24254 - LDC crash on Epyc Bergamo"?
That was fixed within the week, with a notification given that it had been sent to the reporter.
null
I constantly feel like inferior languages are picked up, while superior languages are discarded. It's almost as if the universe had a law: "inferior technology is always preferred no matter how hard you seethe".
Examples:
While Python, TypeScript and Go are quite alright, there is no doubt in my mind that their alternatives are absolutely superior as languages. Yes, in case of Dart, Crystal and D the ecosystem doesn't have the abundance of well-tested libraries, but as languages they are simply better. The Go argument that it's popular because it's simpler is absurd in the sense that no one really forces you to write complex code and use classes or other advanced OOP features in D.