I share your enthusiasm but there are limits. C++ compilation speed (and thus interpretation speed) will make it quite impossible to use it as an extension language. And while I like and use C++ a lot I don't think it is the right language for this purpose. It can do quite a lot of things, but working in a homogeneous language in your extensions as well as your core product doesn't have enough benefits compared to using a systems programming language and an extension language.
> C++ compilation speed (and thus interpretation speed) will make it quite impossible to use it as an extension language.
I think you vastly underestimate the speed of the clang C++ compiler (or any modern C++ compiler at that). I can't imagine that the compilation time for anything that could be classified as an "extension" would be significant in any meaningful way.
clang doesn't outperform gcc on most projects I work on or that speed increase is not significant. I run quite a lot of test-suites - maybe I should try to measure them and provide some real numbers for reference instead of hand-wave myself through this argument.
If I where to provide extensions points to my C++ project they would certainly contain templates and that would also mean that they would require significant compilation time (compared to what you would expect). Even if I didn't, a single header that pulls in a huge preprocessor library could ruin speed. I'm inclined to believe you if we are talking about a Qt-style C++, but that is only a subset of possible code. I would be happy to be proven wrong, too.
> I'm inclined to believe you if we are talking about a Qt-style C++, but that is only a subset of possible code. I would be happy to be proven wrong, too.
If the alternative is to use a separate language altogether to implement extensions, then you are already limiting yourself to a subset of all possible (in C++) code, so what's wrong with doing that in C++ instead?
That being said, most of your problems can be solved with header optimization, we had gotten a full-rebuild of our multimillion line code-base down to about 2 minutes. So if an extension is only a file or two I'm sure you could manage very reasonable compile times, esp with optimization turned off.
> Even if I didn't, a single header that pulls in a huge preprocessor library could ruin speed.
In the case that you really need that header (If you are using as an extension language, it should be designed so you don't!) precompilation of certain units can greatly improve speed. clang in particular has very impressive precompilation support.
Well if it's possible for C++, it's definitely possible for D which is benchmarked to compile 100 times faster and has close-to-ruby's productivity in a close-to-metal language like C. An added benefit is that D already has most of the C++11 features and more.
I would very much like to use D as an extension language.
I can see it being helpful if you are working in C++ all day and need to try small things out. I use LinqPad for doing the same w/ C#, helps when you need to test out some smaller ideas w/o all the cruft of projects and references / includes / etc.
