I know this is a big controversial can of worms, but as a filthy casual who just...

kkylin · on Nov 28, 2018

Not a R6RS fan myself, so no definitive answer. But AFAIK Chez (now open source as someone else posted) is R6RS-compliant and one of the fastest implementations. Also, R7RS-small is final I think. Not sure about R7RS-large. Here's an old discsussion: https://news.ycombinator.com/item?id=11700167.

ballpark · on Nov 28, 2018

I think Chicken Scheme recently became r7rs in their new version 5

Globz · on Nov 28, 2018

Chicken R7RS is still a work in progress AFAIK

gus_massa · on Nov 29, 2018

Racket has an official R5RS and an official R6RS modes (you must start your program with #lang r6rs or with #!r6rs) and also an unofficial R7RS mode.