thank you! the scryer community deserves much of the credit too. everyone is welcome and encouraged to join us at https://github.com/mthom/scryer-prolog! some exciting plans in the pipe
Several innovations are documented in the README. Both the Prolog implementation and the type checker are written in / hosted by Scryer (Prolog implementation is done, the type checker is in progress). Scryer has many powerful constructs for monotonic reasoning which should help to take Shen's type checker in particular to new heights of power!
The ISO standard does not yet say anything about FFIs. I've heard that SWI's FFI is hampered by its garbage collection somehow. Since I'm working on a GC for Scryer now, it's probably a good idea to consider FFI concurrently. "A beginning is such a delicate time." I remember reading that somewhere.
No FFI yet, no. I'll first try to adapt LispWork's Foreign Language Interface by writing a compatibility layer for Rust. If that goes well, I'll begin to explore writing a Common Lisp FFI to Scryer, which may give insights on how to interface Scryer to languages like C and Java.