Replacement language for C++? - programming-languages

When working on hobby projects I really like to program in low-level languages (in the sense that C and C++ are low level). I don't want to work with managed languages with garbage collection and whatnot that takes all the fun away (yeah, we're all different ;-) ).
Normally I use C++ for these type of projects. C++ is rather complex and not so elegant so I have been looking for a language to replace it. Anybody can give me suggestions?
Preferences (not requirements):
should be low-level (like C and C++)
compile to native code (kind of follows from the above but no harm in being explicit)
preferrably target win32/win64
object oriented
statically typed
I have looked at Objective C but I don't like it.

D? (Wikipedia page)
The D language is statically typed and
compiles directly to machine code.
It's multiparadigm, supporting many
programming styles: imperative, object
oriented, and metaprogramming. It's a
member of the C syntax family, and its
appearance is very similar to that of
C++. For a quick comparison of the
features, see this comparison of D
with C, C++, C# and Java.
I think that covers everything in your requirements except Windows support, which it has too.
Note that it has garbage collection, but your question seems to associate garbage collection with being managed - they're not the same thing. I believe garbage collection can be pretty tightly controlled in D.
I should note that I have absolutely no experience in the language whatsoever :)

Ada - http://en.wikipedia.org/wiki/Ada_programming_language
Oberon - http://en.wikipedia.org/wiki/Oberon_(programming_language)
Modula 3 - http://en.wikipedia.org/wiki/Modula-3

Delphi? Pascal syntax, but still quote powerful and just a little more high-level than C++.

Requesting no gc is rather strong and eliminate almost every modern language - things like Ocaml, for example, fill all the other requirements.
There is also ADA which fill every of your desire, but that's a very strict language. The syntax is somewhat similar to Pascal I think, and the language has much less holes compared to C. It has built-in support for threads and 'modules' (better than C headers).

FreePascal
Delphi
Oberon
Any 3 would be great replacements. They're easier to use than C++ too.

Ada is a really good language, however, it uses garbage collections (noticed that mamboking mentioned it.) Not sure about Oberon and Modula 3.
Pascal/Delphi is also using garbage collection as far as I know. (or at least smart pointers of some kind.)

I suggest Limbo!
It's a language created by Rob Pike (co-author with Kerninghan of many programming books). This language is interpreted by the DIS virtual (memory-to-memory) machine or compiled.
It has many data types built in like tuple, pipe, list, array, channel (useful to EASILY comunicate between thread), etc. it's concurrent, modular.
It implements many modern features! and it's used to write application for the Inferno OS.
Limbo review by Dennis Ritchie and
Limbo review by Kernighan

I would suggest Vala! try it is is amazing

Related

Is it true that anything that can be coded in one programming language can be done in any other language?

Is it true that anything that can be coded in one programming language can be done in any other language?
For instance, is it possible to code an Android App in c or c++ instead of Java?
Yes,the only difference being, some languages give inbuilt libraries for certain implementations while in others, you may have to implement it by yourself.
Take for example: consider A and B to be matrices, In Octave you can multiply them by just doing A*B, while in other languages, like C, you should write the full code yourself.
Yes of course no doubt. The only thing is that somethings can be done easily in one programming language while in other it may be a tough one.
This is my personal opinion; it is difficult to answer with 100% accuracy because I do not know the ins and outs of every language that exists but I will try to answer in two parts.
Short answer:
Yes; it is entirely possible to do anything in one language in another language. However, it may be harder to duplicate specific logic across languages.
Long answer:
Although it can be possible to implement the same program/class/software in one language in another language, this is not always the best thing to do.
For example, some languages have advantages over others in specific areas. FORTRAN, C, and C++ are all languages that can produce fast results for math operations when compared to languages like Java or C#. But C# for example, gives you much more flexibility than say C++ with object orientation.
So for example, you have millions of operations that need to be done, and time is important to you - C/C++ would be a better language to implement compared to C#.
But If you cared less about the efficiency, and wanted to leverage the benefits of OOD within C#, then you would use C#.
Note:
I tried to be simple with this example, remember a book could be written on this topic.
A programming language can do anything another can, but certain steps are put in place so they can not. You don't want Javascript calling to your windowAPI and bringing up windows outside your browser, or placing bat files on your computer without your permision

Choose splatform-independent language for math-intensive computations

I am planning on making a flame fractal engine (no GUI), similar to flam3,
but I need to chose a language. I have one such engine made in Java already, but it is too slow.
What I seek is a compiled language, that can be compiled to both windows and Linux (hence no .NET, GPU language), and preferably with garbage collecting and object-orientation (so no C, and C++).
What languages out there, except D, satisfy these conditions?
Any other thoughts on this?
EDIT: I am more after what similar alternatives there is to D, since D is still in development.
I will probably choose D, since it has native support for complex numbers, among other things.
However, C++ is more accessible to other developers, but it is a hard language, in my opinion.
This will undoubtedly start a new flamewar until someone closes the question. My personal opinion is you should use C++, where the missing garbage collection is something you should accept, since manual memory management offers you more performance tuning options.
Google announced a research paper yesterday about a Java / C++ / Go / Scala comparison, you may find it helpful:
https://days2011.scala-lang.org/sites/days2011/files/ws3-1-Hundt.pdf
You made yourself a very tough task (and asked an interesting question, by the way).
The only language that springs to my mind is Ada (it has an optional garbage collector, as discussed in this thread, and according to this book it support object-orientation). This Ubuntu comparison shows that Ada 2005 is quite fast, generally faster in benchmarks than Java, but slower than C/C++.
Disclaimer: I do not claim that Ada is superior to any other language. In fact, I have not used it in any reasonable application. I believe using C++ will produce faster code; moreover, probably the effort required to manage the memory manually in C++ is worth the speed improvement, but I am not an expert in this. This is not to start a flamewar (as #Doc pointed out, it may happen); just my opinion on the topic.
I decided to go for D, since it is closest to what I want.
I was merely curious what other languages that were comparable to D.

How to create a language these days?

I need to get around to writing that programming language I've been meaning to write. How do you kids do it these days? I've been out of the loop for over a decade; are you doing it any differently now than we did back in the pre-internet, pre-windows days? You know, back when "real" coders coded in C, used the command line, and quibbled over which shell was superior?
Just to clarify, I mean, not how do you DESIGN a language (that I can figure out fairly easily) but how do you build the compiler and standard libraries and so forth? What tools do you kids use these days?
One consideration that's new since the punched card era is the existence of virtual machines already bountifully provided with "standard libraries." Targeting the JVM or the .NET CLR instead of ye olde "language walled garden" saves you a lot of bootstrapping. If you're creating a compiled language, you may also find Java byte code or MSIL an easier compile target than machine code (of course, if you're in this for the fun of creating a tight optimising compiler then you'll see this as a bug rather than a feature).
On the negative side, the idioms of the JVM or CLR may not be what you want for your language. So you may still end up building "standard libraries" just to provide idiomatic interfaces over the platform facility. (An example is that every languages and its dog seems to provide its own method for writing to the console, rather than leaving users to manually call System.out.println or Console.WriteLine.) Nevertheless, it enables an incremental development of the idiomatic libraries, and means that the more obscure libraries for which you never get round to building idiomatic interfaces are still accessible even if in an ugly way.
If you're considering an interpreted language, .NET also has support for efficient interpretation via the Dynamic Language Runtime (DLR). (I don't know if there's an equivalent for the JVM.) This should help free you up to focus on the language design without having to worry so much about the optimisation of the interpreter.
I've written two compilers now in Haskell for small domain-specific languages, and have found it to be an incredibly productive experience. The parsec library makes playing with syntax easy, and interpreters are very simple to write over a Haskell data structure. There is a description of writing a Lisp interpreter in Haskell that I found helpful.
If you are interested in a high-performance backend, I recommend LLVM. It has a concise and elegant byte-code and the best x86/amd64 generating backend you can find. There is an optional garbage collector, and some experimental backends that target the JVM and CLR.
You can write a compiler in any language that produces LLVM bytecode. If you are adventurous enough to learn Haskell but want LLVM, there are a set of Haskell-LLVM bindings.
What has changed considerably but hasn't been mentioned yet is IDE support and interoperability:
Nowadays we pretty much expect Intellisense, step-by-step execution and state inspection "right in the editor window", new types that tell the debugger how to treat them and rather helpful diagnostic messages. The old "compile .x -> .y" executable is not enough to create a language anymore. The environment is nothing to focus on first, but affects willingness to adopt.
Also, libraries have become much more powerful, noone wants to implement all that in yet another language. Try to borrow, make it easy to call existing code, and make it easy to be called by other code.
Targeting a VM - as itowlson suggested - is probably a good way to get started. If that turns out a problem, it can still be replaced by native compilers.
I'm pretty sure you do what's always been done.
Write some code, and show your results to the world.
As compared to the olden times, there are some tools to make your job easier though. Might I suggest ANTLR for parsing your language grammar?
Speaking as someone who just built a very simple assembly like language and interpreter, I'd start out with the .NET framework or similar. Nothing can beat the powerful syntax of C# + the backing of the entire .NET community when attempting to write most things. From here i designed a simple bytecode format and assembly syntax and proceeeded to write my interpreter + assembler.
Like i said, it was a very simple language.
You should not accept wimpy solutions like using the latest tools. You should bootstrap the language by writing a minimal compiler in Visual Basic for Applications or a similar language, then write all the compilation tools in your new language and then self-compile it using only the language itself.
Also, what is the proposed name of the language?
I think recently there have not been languages with ALL CAPITAL LETTER names like COBOL and FORTRAN, so I hope you will call it something like MIKELANG with all capital letters.
Not so much an implementation but a design decision which effects implementation - if you make every statement of your language have a unique parse tree without context, you'll get something that it's easy to hand-code a parser, and that doesn't require large amounts of work to provide syntax highlighting for. Similarly simple things like using a different symbol for module namespaces and object namespaces ( unlike Java which uses . for both package and class namespaces ) means you can parse the code without loading every module that it refers to.
Standard libraries - include the equivalent of everything in C99 standard libraries other than setjmp. Add whatever else you need for your domain. Work out an easy way to do this, either something like SWIG or an in-line FFI such as Ruby's [can't remember module name] and Python's ctypes.
Building as much of the language in the language is an option, but projects which start out doing either give up (rubinius moved to using C++ for parts of its standard library), or is only for research purposes (Mozilla Narcissus)
I am actually a kid, haha. I've never written an actual compiler before or designed a language, but I have finished The Red Dragon Book, so I suppose I have somewhat of an idea (I hope).
It would depend firstly on the grammar. If it's LR or LALR I suppose tools like Bison/Flex would work well. If it's more LL, I'd use Spirit, which is a component of Boost. It allows you to write the language's grammar in C++ in an EBNF-like syntax, so no muddling around with code generators; the C++ compiler compiles the grammar for you. If any of these fail, I'd write an EBNF grammar on paper, and then proceed to do some heavy recursive descent parsing, which seems to work; if C++ can be parsed pretty well using RDP (as GCC does it), then I suppose with enough unit tests and patience you could write entire compilers using RDP.
Once I have a parser running and some sort of intermediate representation, it then depends on how it runs. If it's some bytecode or native code compiler, I'll use LLVM or libJIT to process it. LLVM is more suited for general compilation, but I like the libJIT API and documentation better. Alternatively, if I'm really lazy, I'll generate C code and let GCC do the actual compilation. Another alternative, is to target an existing VM, like Parrot or the JVM or the CLR. Parrot is the VM being designed for Perl. If it's just an interpreter, I'll walk the syntax tree.
A radical alternative is to use Prolog, which has syntax features which remarkably simulate EBNF. I have no experience with it though, and if I am not wrong (which I am almost certainly going to be), Prolog would be quite slow if used to parse heavy duty programming languages with a lot of syntactical constructs and quirks (read: C++ and Perl).
All this I'll do in C++, if only because I am more used to writing in it than C. I'd stay away from Java/Python or anything of that sort for the actual production code (writing compilers in C/C++ help to make it portable), but I could see myself using them as a prototyping language, especially Python, which I am partial towards. Of course, I've never actually done any of this before, so I'm not one to say.
On lambda-the-ultimate there's a link to Create Your Own Programming Language by Marc-André Cournoyer, which appears to describe how to leverage some modern tools for creating little languages.
Just to clarify, I mean, not how do you DESIGN a language (that I can figure out fairly easily)
Just a hint: Look at some quite different languages first, before designing a new languge (i.e. languages with a very different evaluation strategy). Haskell and Oz come to mind. Though you should also know Prolog and Scheme. A year ago I also was like "hey, let's design a language that behaves exactly as I want", but fortunatly I looked at those other languages first (or you could also say unfortunatly, because now I don't know how I want a language to behave anymore...).
Before you start creating a language you should read this:
Hanspeter Moessenboeck, The Art of Niklaus Wirth
ftp://ftp.ssw.uni-linz.ac.at/pub/Papers/Moe00b.pdf
There's a big shortcut to implementing a language that I don't see in the other answers here. If you use one of Lukasiewicz's "unparenthesized" forms (ie. Forward Polish or Reverse Polish) you don't need a parser at all! With reverse polish, the dependencies go right-to-left so you simply execute each token as it's scanned. With forward polish, it's the reverse of that, so you actually execute the program "backwards", simplifying subexpressions until reaching the starting token.
To understand why this works, you should investigate the 3 primary tree-traversal algorithms: pre-order, in-order, post-order. These three traversals are the inverse of the parsing task that a language reader (i. parser) has to perform. Only the in-order notation "requires" a recursive decent to re-construct the expression tree. With the other two, you can get away with just a stack.
This may require more "thinking' and less "implementing".
BTW, if you've already found an answer (this question is a year old), you can post that and accept it.
Real coders still code in C. Just that it's a litte sharper.
Hmmm... language design? or writing a compiler?
If you want to write a compiler, you'd use Flex + Bison. (google)
Not an easy answer, but..
You essentially want to define a set of rules written in text (tokens) and then some parser that checks these rules and assembles them into fragments.
http://www.mactech.com/articles/mactech/Vol.16/16.07/UsingFlexandBison/
People can spend years on this, The above article talks about using two tools (Flex and Bison) That can be used to turn text into code you can feed to a compiler.
First I spent a year or so to actually think how the language should look like. At the same time I helped in developing Ioke (www.ioke.org) to learn language internals.
I have chosen Objective-C as implementation platform as it's fast (enough), simple and rich language. It also provides test framework so agile approach is a go. It also has a rich standard library I can build upon.
Since my language is simple on syntactic level (no keywords, only literals, operators and messages) I could go with Ragel (http://www.complang.org/ragel/) for building scanner. It's fast as hell and simple to use.
Now I have a working object model, scanner and simple operator shuffling plus standard library bootstrap code. I can even run a simple programs - as long as they fit in one file that is :)
Of course older techniques are still common (e.g. using Flex and Bison) many newer language implementations combine the lexing and parsing phase, by using a parser based on a parsing expression grammar (PEG). This works for recursive descent parsers created using combinators, or memoizing Packrat parsers. Many compilers are built using the Antlr framework also.
Use bison/flex which is the gnu version of yacc/lex. This book is extremely helpful.
The reason to use bison is it catches any conflicts in the language. I used it and it made my life many years easier (ok so i'm on my 2nd year but the first 6months was a few years ago writing it in C++ and the parsing/conflicts/results were terrible! :(.)
If you want to write a compiler obviously you need to read the Dragon Book ;)
Here is another good book that I have just read. It is practical and easier to understand than the Dragon Book:
http://www.amazon.co.uk/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=language+implementation+patterns&x=0&y=0
Mike --
If you're interested in an efficient native-code-generating compiler for Windows so you can get your bearings -- without wading through all the unnecessary widgets, gadgets, and other nonsense that clutter today's machines -- I recommend the Osmosian Order's Plain English development system. It includes a unique interface, a simplified file manager, a friendly text editor, a handy hexadecimal dumper, the compiler/linker (of course), and a wysiwyg page-layout application for documentation. Written entirely in Plain English, it is a quick download (less than a megabyte), small enough to understand in short order (about 25,000 lines of Plain English code, with just 4,000 in the compiler/linker), yet powerful enough to reproduce itself on a bottom-of-the-line Dell in less than three seconds. Really: three seconds. And it's free to all who write and ask for a copy, including the source code and and a rather humorous tongue-in-cheek 100-page manual. See www.osmosian.com for details on how to get a copy, or write to me directly with questions or comments: Gerry.Rzeppa#pobox.com

Programming language with native code support, No framework (I write the framework)

I'm looking for a programming language. It should be an easy language to learn, and should have a Garbage Collector. It should be a basic language with features like basic types (integer, boolean), arrays and etc, and I should write the framework.
It is for a game editor I want to write. The editor's designer will write the code of the UI in this programming language. The framework will be a 2D graphics and audio framework, and in the future it'll be 3D too.
I thought about the new Go language, but it doesn't have much support and theres no binding to OpenGL and etc.
Any ideas?
Thanks.
The obvious two are [C](http://en.wikipedia.org/wiki/C_(programming_language)) or C++. However, [D](http://en.wikipedia.org/wiki/D_(programming_language)) is closer to Java and C# given that it has a garbage collector in the standard, as well as an alternative standard library that is fairly closer to Java than the C++ standard library. The downside with D is that they tools are not as mature as C++ or C and the community isn't as large.
The obvious solution though it to look down the list of compiled languages on wikipedia and see which you like the look of.
Well, that's a fairly broad question and without more specific requirements it is difficult to give a focused answer, but it sounds like C (or C++) would fit the bill for you. The languages you described all owe their syntax to C. C will compile to native code. C is basic language in that there is not much to learn beyond the basic syntax and it has all the basic primitives that you require.
Now that you've added the requirement of a garbage collected language, I suppose that you could try Go, but that language is not mature and there's always a risk there.
If you don't want to manage memory all by yourself like C or C++, you can try the new Go language. It compiles to native code (albeit for Linux and MacOSX only for now) and comes with a basic framework that can be easily replaced with your own framework.
It has a very active user base, so IMO it is possible to mature quickly.
You may want to look at Lua.
Lua is a relatively tiny language which manages to be capable and universal with just a few concepts. The BNF specification for the whole language fits easily on one page. It has numbers, booleans, tables and functions, and surprisingly that's all the datatypes it needs. It can even work in an object-oriented fashion.
There's a compiler, Luac, that compiles Lua to bytecode.
Lua is already being used as a UI programming language for games. Addons for World of Warcraft and a few other games are programmed in Lua. I believe Lua is a very good fit for this kind of task.
You want OpenGL? OK... http://luagl.wikidot.com/ is an OpenGL library for Lua.
Since we don't know what you want to do, I don't know what are the chances we success. Therefor, what about a language where you have to set the probability of your statement to fail :
Meet GOTO++.
Don't say "thanks you", it's on me.
Enjoy a challenge?
Try go.
Here's a tech talk by rob pike, and here is a discussion group: http://groups.google.com/group/golang-nuts/topics
.
C++ is Great, it's not scripting lang, so you don't even need a scripting host.

Which language would you use in your OS?

This is probably more of a subjective question, but which language (not API like .NET or JDK) would you use should you write your own operating system? Which language provides flexibility, simplicity, and possibly a low-level interface to the hardware? I was thinking Java or C...
C, of course.
Haskell.
Once you have flipped the right hardware bits, C is a terrible language to use for the rest of the OS. Things like the scheduler, filesystems, drivers, etc. are complex high-level algorithms, and you don't want to be writing those in assembly language (or C; same thing). It's too hard to get right. (The VM subsystem and memory manager may need to be written in something low-level, as you will need to bootstrap your high-level langauge's runtime somehow.)
Anyway, this isn't just a crazy idea that I am coming up with for SO. Here is an OS written in Haskell: http://programatica.cs.pdx.edu/House/
Lisp is another good choice; the original Lisp machines were infinitely more tweakable (at runtime) than "modern" OSes like UNIX and Windows.
Sometimes history forgets good ideas (often in the name of "maximum performance"), and that makes me sad.
D would be an interesting choice. From its own description:
D is a systems programming language. Its focus is on combining the power and high performance of C and C++ with the programmer productivity of modern languages like Ruby and Python. Special attention is given to the needs of quality assurance, documentation, management, portability and reliability.
The D runtime assumes the existence of a garbage collector, which would not be appropriate for the very lowest levels of the kernel. However, it would be appropriate for many of the higher layers.
Build the basic components like task schedulers and drivers etc with Assembly, then build the higher level components like applications and tools with C
I believe this is how Windows XP was built too (unsure about Windows Vista and Windows 7).
Definitely... C
C, ASM, C#
Singularity
Low-level in something like Haskell or D. Productivity over performance, in my opinion. You can rewrite slow parts in C++ or even assembly later if the need arises.
High-level in Python or Ruby. Ideally I'd also have a really fast JIT-capable VM for that language, but that's not going to happen for either language for a while. Lua would be a good alternative if speed gets in the way.
The kernel has to be written in a low-level language, C is by far the best choice for this, because it is so memory efficient. The higher levels could be built with a combination of Java or more ideally Objective-C, and scripting languages like python and ruby, or lua.
Honestly, I would either use C or some hierarchy of languages that I had either designed or fit together completely seamlessly. What I would be looking for is a seamless experience that starts at the bare metal level and then I could move to higher and higher level languages as I moved up the problem space. I would probably chose something like:
C - for bare metal stuff like drivers, kernel, etc
Java/C# - for application-level things like administration consoles, OS apps
Python/PowerShell - for scripting activities like common administrative tasks (creating a new user, etc)
Personally, I think C/C#/PowerShell is more tightly integrated and the type of experience I'd be looking for. Of course, if I ever got so ambitious as to write an OS, I would have a lot of spare time on my hands and would probably really enjoy tackling the language stack first. So maybe it would be L/L#/LScript ...
BitC seems to have this in mind. Despite it's name it seems to be the midpoint of assembly language and lisp. The goal was to make a language with a strong correspondence with machine language but have an intermediate representation that supports stronger correctness inferences than is possible with most other common languages. The languages was created as part of the Coyotos project, an operating system with lofty goals of security and reliability. Formal verification is made significantly possible with the ir used in BitC.
Ada:
Ada is a structured, statically typed, imperative, and object-oriented high-level computer programming language, extended from Pascal and other languages. It was originally designed by a team led by Jean Ichbiah of CII Honeywell Bull under contract to the United States Department of Defense (DoD) from 1977 to 1983 to supersede the hundreds of programming languages then used by the DoD. Ada is strongly typed and compilers are validated for reliability in mission-critical applications, such as avionics software.
Ada, because it was not only specifically developed for such projects, but it also provides support for several very useful high level features (such as support for strong typing, concurrency and abstraction) that are simply not available in standard C.
So that, even as a project grows, you don't have to work around language limitations (think encapsulation, abstraction, namespaces in C).
Don't get me wrong, C works obviously for a great many of projects, but once a project has gained a certain size (think Linux kernel, gcc, GNOME), you will inevitably appreciate certain features of more high level languages to make the development process less tedious and also less obfuscated.
In C however, these features usually end up being -pretty poorly- emulated by excessive and almost pervert use of the pre-processor (this can for example be seen in the gcc code base), so that you get to see lots of nested macros, that from an implementation point of view, actually emulate features found in other programming languages.
In addition, Ada is the only programming language, that I am aware of, that actually provides standardized support for source code analysis using the ASIS, having such a facility in place is however the prerequisite to actually be able to maintain and transform/re-engineer a code base in the long run (think refactoring).
Having an interface like ASIS available, means that you can actually implement "semantic patching", where you can automatically rename a file, function or variable/data structure and it will actually work.
Java ?? no jave runs on a virtual machine which needs an os to run on top of ,
maybe C and some ASM ;)
I would go with D to see whether it can do it.
I would only pick the following 3 out of practicality.
C (good old fashioned)
C++ (C with stuff tacked on. Windows is partially written in this)
Java (the medium level language that just might have a capable garbage collector with controllable pauses with G1).
If I were going to start a new OS I'd do it with the subset of C++ recommended by the embedded industry. You can use things like classes and use it "as a better C" and be just as fast. Just avoid things that have massive overhead. You can even use some template features, if you stick to a certain subet that basically don't have any overhead. Look on embedded.com for features in C++ that have little to no overhead, but will allow you organize your code better than you ever could in C.
Oberon? I guess I miss Pascal too much some times. C paid the bills for quite a while, but I don't really love it.
Lisp of course!
Title text: Some say the world will end in fire; some say in segfaults.
For an OS, you want speed at the lowest levels. So assembly, C, C++, Objective-C, or Java seem to be the current choices. Although it's just recently that Java got fast, and it's hard for me to imagine an OS with garbage collection.
If I were writing my own, it would be a mix of assembly and C.
A C or C++ microkernel with a JIT for a highly dynamic language like Ruby or maybe a language with native support for the Prototype pattern. Even device drivers in that language.
Not because it's practical but because it's really cool. Cool in the way that NeXTStep was cool for using Obj-C for pretty much everything.
http://www.dwheeler.com/sloc/redhat71-v1/redhat71sloc.html - share of languages in Linux's source code.
C, by a number of reasons. Other candidates, like D, are great. However, C has this advantage: there's a lot of available open-sourced C code that you could reuse in your project (much more than is for other languages appropriate for system programming).
I would be torn between using some existing low level language and write my own based on C# but with much better generics support.
In second case I would make each method generic, but all the constraints will be resolved by compiler - to allow "duck typing" like in Scala but still language should be static. Also static virtual methods would lower the codebase.
I've had that idea for a long time, but it never seems to be doable in real timeframe, so who knows maybe in the future. :-)
Some would say Java.
Note that openfirmware is written partly in Forth, and it's very low level.
Have an open mind.
"The kernel has to be written in a low-level language, C is by far the best choice for this, because it is so memory efficient. "
Um... What about FORTH?
FORTH can be low level and high level, so you could have a whole operating system written in FORTH from the ground up, and still have a nice easy REPL scripting environment on top, also in FORTH.
However, any decent operating system should support lots of langauges on top, from C all the way to Python Ruby and Javascript. Making FORTH the basis for it all has a lot of benefits though.
edit: I'd only ever attempt this for an embedded environment with a single known hardware set. Trying to write an OS that could compete with Linux or Windows is a fools job.
If this isn't a hypothetical question, and you're looking to create your own OS, I'd probably go with C because most of the examples out there are written in C.
Also, (And I haven't build an OS yet so take this with a grain of salt), I'm thinking that the c runtime libraries would be a lot easier to port to your new OS than say .NET.
Pascal + Oberon: they have the power of C and C++ but they're not as daunting to use. Both these languages are grossly under appreciated.

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