We have a macro expander for pascal written in scheme (quick and dirty draft made by me that worked so well it stayed). We had some performance problems with some crazy recursive macros (it generates a _lot_ of code. Don&#x27;t ask, I am not allowed to talk much about it), so I investigated porting it to chez.<p>Instead I just switched to  guile (scheme implementation) trunk and got a 3x speedup. Did some optimizing work and it ended up at 4x, which is good enough.