OberonScript: a safe scripting language and runtime for web apps (2007)
ralphsommerer.com
ralphsommerer.com
Does the language do anything that Dart doesn't?
2007 probably needs to be added to the title. I get the feeling that progress is a bit slower than anticipated.
Oberon is one of the confusing family of Oberons that come from a confusing family of Modulas that comes from Pascal. Most of them come from Niklaus Wirth or try to build on his ideas.
The reason I say confusing is that, for example, there's no one Oberon. There's Oberon, Oberon 2, Active Oberon etc [1]. They differ in things like
- they may or may not have things like for loops
- they may or may not have various OOP features
- they may or may not have pointers
- they may or may not have three different types of looping constructs with different constraints (you can exit a do loop, but not a while loop etc.)
and so on, depending on ... well depending on nothing but Wirth's ideas of what a programming language should be. There are at least two OSes built with Oberon: Oberon and Bluebottle.
There are fans of this family of languages, and I've even participated in discussions (on a Russian programming forum) where people would defend to the death the choice of three different loop constructs with different semantics (you can break inside LOOP, but not inside FOR or WHILE etc.), or the difference between procedure and function etc.
[1] https://en.wikipedia.org/wiki/Oberon_(programming_language)
Sounds rather shallow to me, really. I can see the point in building a kernel in the safe subset of Rust, to provide strong assurances about memory-management. I can see the point in building a kernel in SPARK to provide even stronger and more general assurances of correctness. I see the point in developing a kernel using a fully formal methodology, like Sel4. I can see the fun in hand-tuned kernels written in assembly, like KolibriOS. What's interesting about using a language with slightly different imperative building-blocks? Rust wouldn't be worth learning if it were merely C with different iterative statements.
Or are there significant advantages to the various Oberons, that I'm unaware of?
Iirc, Wirth achieved some relatively lean but powerful languages at some point.
Also, I don't understand your opposition to writing a kernel in some form of Oberon, but accepting pretty much any other language/paradigm ?
¹ Not that there is only _one_ optimal language.
When people talk about developing a kernel in a language other than C, the question that springs to mind is So what does this choice of language bring to the table?
Rust and especially SPARK bring significant assurances of correctness, as they both improve greatly on the unsafety (supposing that's a word) of the C language.
The same is true of a middle-of-the-road language like Java, but Java isn't ideally suited to kernel development. (If OS researchers prove me wrong on this point, then that's great, of course.)
Assembly isn't a very compelling choice of language in terms of safety/correctness assurances, but I can see the appeal for a hobbyist OS, or for a carefully tuned high-performance codebase.
From what I know of Oberon, using it for kernel development isn't in itself very interesting. Does it offer the guaranteed absence of broad categories of runtime errors? I guess it's still probably a rather safer language than C, and I presume its performance is ok, but this isn't anything new.
(Of course, I've only talked about language. There are plenty of other ways an OS can be interesting besides the language it's implemented in, but that's the topic at hand.)
Microsoft had an experimental OS called Singularity [1]
--- start quote ---
The lowest-level x86 interrupt dispatch code is written in assembly language and C. Once this code has done its job, it invokes the kernel, which runtime system and garbage collector are written in Sing# (an extended version of Spec#, itself an extension of C#) and runs in unprotected mode.
--- end quote ---
And don't forget that SIM cards in your phone run a Java... -ish [2,3]
[1] https://en.wikipedia.org/wiki/Singularity_(operating_system)
[2] https://www.defcon.org/images/defcon-21/dc-21-presentations/...
Then besides JX, there was SquawkVM for SPOT, Solaris research for Java drivers, and embedded vendors like PTC and Aicas do support bare metal Java runtimes, which is basically an OS at that point.
I must admit I was a user of the system many years before I read the book, and I enjoyed reading the book considerably more than working with the system, but it's still a gem of a design. [Edited to fix link]
In the case of Sel4, yes. The ARMv7 assembly code has been shown to be free of bugs. [0][1]
SPARK Ada does not have a formally verified compiler, but there are various Ada compilers that are approved for use in life-and-death applications. The Boeing 777 flies on Ada code, for instance. [2] To my knowledge, compiler bugs aren't a major practical concern for SPARK, although a formally verified compiler would be a great addition.
C has a fully verified compiler in CompCert. [3] I know of no other language with a fully verified compiler. (CompCert supports almost all C features, so it will either produce a valid binary for the input C code, or else fail with an error.)
Rust has a bit of a history of troublesome compiler bugs. I think we're a way off seeing Rust used in critical systems, assuming it would even make sense to use a language like Rust. Memory management is handled quite differently in applications like avionics.
> Can a single person fully understand them?
The compilers/linkers? I imagine the most well-informed developers on the Rust and Ada compilers pretty much know how everything works, but really that's just a guess. If someone were to make a compiler specifically for SPARK, it could be simpler than a full Ada compiler, as SPARK forbids most Ada features. I don't know that this is likely to happen though.
[0] https://docs.sel4.systems/projects/sel4/frequently-asked-que...
[1] https://sel4.systems/Info/FAQ/proof.pml
[2] http://archive.adaic.com/projects/atwork/boeing.html (This is about Ada, and is not specifically about the SPARK subset)
It's a general purpose language you're comparing to other general purpose languages, so of course.
The different versions of oberon, ok, but look at the different versions of C#, scala, SQL, C++ etc etc.
> on nothing but Wirth's ideas of what a programming language should be
Produce something as good as pascal and then I'll be impressed (I've tried and it isn't easy). Wirth is a deeply competent language designer, the diss is undeserved.
He is a competent language designer, but his ideas about what a language should be are strange at best, and this is reflected in the languages he designs.
While Pascal was (and in many ways still is) a gem for its own time, all of the languages he produced since have been hardly more than a regurgitation of the same ideas, with a strange fixation on the "procedural programming purity at any and all costs" (hence the chase for a loop construct you can't exit, single-return procedures/functions etc.)
The looping issue is because modelling it - that is, giving it clear and simple formal semantics - was not trivial. The single-point of exit stuff is also there for the same reason. I'd agree that it's possibly not a good choice given the alternatives if you are doing non-verified code, but he had his reasons.
If you ever wonder why modula-3's garbage collector only collected memory, you could not hook into it in the form of a destructor for management of resources other than memory, go and read up the complexities that being able to piggyback on a destructor brings. It gets bad.
We could have some agreement but with "regurgitation", "strange fixation", "strange at best#" - this is the sound of you not understanding and not realising it, not wirth's deficiencies.
If you think you can do better then go ahead. You'll learn a lot.
Here's the Wikipedia page on the topic: https://en.wikipedia.org/wiki/Object_resurrection
Literally hundreds of programming languages have loops without unnecessary and random constraints
> The single-point of exit stuff is also there for the same reason.
The same reason of what exactly?
> I'd agree that it's possibly not a good choice given the alternatives if you are doing non-verified code
At what point Oberon code becomes verified?
> If you think you can do better then go ahead.
I realise that you haven't left Wirth's lab for the past 30 years, but there are hundreds of programming languages. Go ahead, you'll learn a lot.
Hm? show me the 'unnecessary and random constraints' in looping. It was fundamental to the semantics that looping wasn't simple formally IIRC
> he same reason of what exactly?
It's literally there in the preceding sentence.
> At what point Oberon code becomes verified?
It didn't (AFAIK), hence my "possibly not a good choice". But as you don't know history, https://en.wikipedia.org/wiki/Euclid_(programming_language) which "is descended from the Pascal programming language". IIRC the london underground train controller software was done with euclid. Please note the wide range of restrictions in the language - all for simplicity, from which reliability must in part depend.
> I realise that you haven't left Wirth's lab for the past 30 years,
don't be insulting
> but there are hundreds of programming languages. Go ahead, you'll learn a lot.
Like: scala? And C#? VB.net, VBScripting, a little bash, pascal, modula2, delphi, javascript, a flex/bison & antlr, python, sql, prolog (edit: C & C++) - these are all langs I've used commercially. If you want langs I've played with the list includes dylan, haskell, erlang, modula3 and others I can't think of now.
Like I said, If you think you can do better then go ahead.
Edit: what your angry reaction is concealing from you is I'm not unsympathetic to your view, but you can't see it and won't learn from it.
> don't be insulting
Let's see about "my" reactions and "being insulting"
- Unlike you I actually know about this stuff
- this is the sound of you not understanding and not realising it
- If you think you can do better then go ahead. You'll learn a lot.
Take your holier than thou attitude and shove it where the sun don't shine.
And if we look at his languages at continued attempts to find the optimum of that space they represent a great resource to tap into - decades of effort to find exactly the right primitives and featureset for the task. That doesn't mean they are the ones to use for all jobs, but "what did Wirth do" is a great starting point.
Edit: and by extraordinary coincidence PBH pops up on HN right now https://news.ycombinator.com/item?id=24913959
And the people in Wirth's orbit (The OberonScript author did his PhD with Wirth) were naturally interested in programming languages, and the compilers were small and well designed, so they were easy to modify.
Last of all, while Wirth is a very practical guy (having designed multiple workstations full-stack), but he never pursued commercial practicality or industrial applicability as an objective in itself. He'd rather pursue whatever his research agenda at the time was, and if industry found something useful to pick up, good for them.
No. But Oberon demonstrates how one can implement real systems with a very little language; and with an extremely small footprint compared to Dart (you can fit a whole operating system into one or two megabytes). There are a lot of other differences; Oberon is a truly statically/strictly typed language wheras the type system in Dart is intentionally optional; you can write an Oberon parser in a couple of hours (in contrast to more complex and ambiguous languages like Dart or Go). Oberon was optimized for use as an educational language and was successfully used for this purpose e.g. at the ETH Zurich. Wirth wanted the minimum necessary for his language, without unnecessary luxury, which only increases the development and learning effort.
(Curiously I was saying just the same thing yesterday about Tcl - https://news.ycombinator.com/item?id=24898886 )