I check out the “Scheme universe” every couple years or so, and it’s a big and varied place now!
I was aware of “Guile and Chicken” a decade ago.
- Chez was open-sourced
- Racket (re-)built itself on top of Chez
- R7Rs became a reality
- Gambit has been around for a while, I was simply ignorant
- Guile got a lot of upgrades (including a JIT) and is the basis for Guix
- Gerbil scheme got built on top of Gambit
If someone’s looking to dip their toes in this universe today, they’re really spoilt for choice, between very high-performant implementations (Chez and Gambit/Gerbil), pretty well-supported ones (Racket & Guile).