Stalin is an aggressively optimizing Scheme compiler. It is the most highly
optimizing Scheme compiler, and in fact one of the most highly optimizing
compilers of any sort for any language. Stalin is publicly & freely available,
licensed under the GNU GPL. It was written by Jeffrey M. Siskind.

In detail, Stalin is a whole-program compiler that uses advanced flow
analysis & closure conversion techniques. It compiles Scheme to highly optimized
C. Stalin has a few very significant limitations, however:
- it takes a long time to compile anything including the compiler
- it is not designed for interactive use or debugging
- it does not support R4RS/R5RS high-level macros
- it does not support the full numeric tower