turtles

g. You program in Lisp (specifically a variant of Scheme) on a larger system; it then compiles to a VM that runs on the target. Currently it does not support the 6502, but the system is designed to be portable and it looks to me that it'd be relatively easy to port to a 6502. Lysp [7] (MIT license) is another small implementation of Lisp. It doesn't directly support 6502 and is in C, but it's small... so it might not be hard to transliterate. A related program from the same developer is Maru [8], which can self-host. This could be a reasonable starting point for creating a 6502 Lisp. Turning the Apple //e into a lisp machine, part 1 [9] refers to this Lisp interpreter for the Apple //e [10] (MIT license). They also show a clever bootstrap approach: they send code via the audio jack (!). There's more that can be done; Lisp was originally developed in 1965, on even smaller systems. The book "Lisp in Small Pieces", Program Transformation in Lisp [11], this Scheme page [12] and these details on implementation [13] are all of interest. R. Kent Dybvig's "Three Implementation Models for Scheme" [14] shows how to implement Scheme while still keeping most stuff on the stack. Tagging could be difficult, but an alternative (that I believe was done for early Lisp implementations) is to partition the memory into regions; to determine the tag, just check which memory region it is in. It might be possible to start with PicoLisp [15] to create a 6502 version. There is a trivial ACL2 implementation of Lisp (GPL) [16] that I converted into Common Lisp ( compiler [17], run-time [18]; See Wolfgang Goerigk's "Compiler Verification Revisited" [19] for more). I know that there was an "InterLISP 65" available for Atari's 6502-based line. Various full LOGO implementations were available as well. [1] skimp: http://web.archive.org/web/20100131151915/http://www.ip9.org... [2] discussion: [missing] [3] Three Implementation Models for Scheme: https://web.archive.org/web/20160817185323/http://www.cs.ind... [4] neslisp: https://web.archive.org/web/20160319025751/http://gomez.yell... sources: https://web.archive.org/web/20160619185108/http://gomez.yell... [5] google code nelisp: [missing] [6] Picobit: https://web.archive.org/web/20150106110223/https://github.co... current: https://github.com/stamourv/picobit [7] Lysp: https://web.archive.org/web/20180929064442/http://piumarta.c... source: browse: https://web.archive.org/web/20170507045957/http://www.piumar... download: https://web.archive.org/web/20180929064442/http://piumarta.c... [8] Maru: https://web.archive.org/web/20181206222700/http://piumarta.c... source: browse: https://web.archive.org/web/20181206222700/http://piumarta.c... download: https://web.archive.org/web/20181206222700/http://piumarta.c... [9] Turning the Apple //e into a lisp machine, part 1: https://web.archive.org/web/20190109003417/http://blog.nulls... [10] google code turtles: https://web.archive.org/web/20180611002847/https://github.co... current: https://github.com/hausdorff/turtles [11] Program Transformation in Lisp: http://www.findinglisp.com/blog/2004/06/program-transformati... [12] this Scheme page: [missing] [13] these details on implementation: https://web.archive.org/web/20180801195133/http://library.re... [14] Three Implementation Models for Scheme: https://web.archive.org/web/20190503102138/https://cs.indian... [15] PicoLisp: https://web.archive.org/web/20181124064229/http://www.softwa... [16] ACL2 implementation of Lisp (GPL): https://web.archive.org/web/20090217043459/http://www.cs.ute... [17] compiler: https://web.archive.org/web/20160320015734/http://www.dwheel... [18] runtime: [missing] [19] Compiler Verification Revisited: [missing] citation: https://dl.acm.org/citation.cfm?id=369101 buy chapter: https://link.springer.com/chapter/10.1007/978-1-4757-3188-0_...