CLASP is a really interesting project.

For one, it's created and written by a Chemistry PhD researcher (Christian Schafmeister), not someone with a traditional CS background.

For another, it's one of the few languages that has ever attempted to interface with C++ at the template level - you can instantiate C++ template classes from CL, and catch C++ exceptions etc.

For yet another, he does compacting garbage collection for the C++ objects used in the CL implementation, with pointer patching and everything else.

There's a nice Google Tech Talk about it [0], that goes into both why he did this, and how he implemented this.

[0] https://www.youtube.com/watch?v=8X69_42Mj-g

Dr Schafmeister is occasionally present on the LLVM Discord. The CLASP project is something else. That hour-long talk he gives on Youtube about it blew my mind.

I guess it helps that it is pretty much a Lisp for the research work that they are doing, instead of trying to cater to everyone.

Last I checked SBCL and CCL (both open source native compiled CL implementations) are quite a bit faster than Clasp.

However, if you are primarily e.g. calling computational chemistry libraries written in C++, Clasp is the way to go. It's the only non-C++ language implementation I know of with actually usable C++ support.

C++/CLI comes to mind, as means to merge .NET and C++ worlds together.

Oh gosh, I forgot about that. Is that Windows only though? I remember MSVC had managed/unmanaged C++ and allowed calling between the two.

Sadly yes.

And although they don't have much love for it, they still keep it relatively up to date.

It was one of the .NET Core 3.1 main milestones.

However I would say for the purpose of binding .NET and C++, probably it doesn't need to understand everything anyway.

The C++/CLI compiler is definitely Windows-only. But I'm not sure whether the generated code would be, if you compile with /clr:pure (which can still handle everything except for setjmp/longjmp).

/clr:pure has been deprecated for some time now, unfortunately. But older compilers are still around...