Historically the Scheme48 abstract machine was written in Pre-Scheme, a Scheme subset restricted enough to compile straightforwardly to C.

For me, using Pre-Scheme to write graphics kernels was great fun, and produced decently fast code :)

Historically? It still is! :)

I think VLISP is, as well. VLISP (not the French one from the 80s, the other one, though the French one was interesting in its own right [1]), was a verified Scheme implementation written in a verified version of Pre-Scheme. Sweet research project, but I haven't seen any public releases of it :/

There are some papers about both here: http://library.readscheme.org/page8.html

[1]: http://www.artinfo-musinfo.org/en/issues/vlisp/index.html

VLISP was a precursor to Le-Lisp [2], which was massively popular and influential in Europe, and could run faster on commodity hardware than Lisp Machine Lisp on the Symbolics 3600.

[2]: http://lelisp.org/ (under construction, but with some useful links for the time being).

France was actually a hotbed of Lisp across the pond and, along with the UK, pretty invested in a European standard for Lisp, first EuLisp (which was an excellent language but somehow flopped unfortunately) and ISLISP (an ISO standard that's not so excellent -- basically a crippled version of Common Lisp -- and also pretty much flopped). I've been in talks with some of the Le-Lisp guys about the possibility of open-sourcing Le-Lisp now that it's no longer commercially viable -- fingers crossed! :)

P.S., if anyone from INRIA happens to be reading this: pretty please?? Jérôme agrees! :)

Large part of low-level runtime of Gauche (Scheme dialect) is written in "C in S-expression", the same idea with this.

I found it so pleasant writing C in S-expr that I gradually rewriting my C code with it.

I'd be surprised if something exactly like this but more mature and with a lot more questionable legacy design decisions doesn't already exist.

There's L++: https://bitbucket.org/ktg/l

And, for people who refuse to let go of curly braces, there's this shameless plug: https://github.com/eudoxia0/cmacro

There is the GSL by iMatix https://github.com/imatix/gsl (so closely associated with Pieter Hintjens of http://zeromq.org/)