Hi,
I have a minimal LISP-1.5-resembling interpreter in C that now can also interpret itself
https://gitlab.com/janneke/mesIt was inspired by the seemingly often ignored bootstrapping question made so painfully visible by GuixSD and by OriansJ with their self hosting hex assembler project.
As a next step after a hex assembler I was thinking of getting Scheme up and running and use that to create a tiny C compiler, probably using PEG. For that I think we need define-syntax, which I had a peek at and still scares the all-sorts-of-things out of me :-)
I searched for minimal Lisp/Scheme to get that going and found an article called the Maxwell Equations of Software with a pointer to the 1962 LISP 1.5 paper by John McCarthy.
First I `implemented' Mes/LISP-1.5: the bottom half of page 13 and the necessary helper procedures defined on pages 8-12 using Guile, removing all but the primitives needed to run LISP-1.5/Mes (I think): car, cdr, cond, cons, define, eq?, '()/nil, null?, pair? and quote. I cheated with read, and with display and newline for debugging.
Then I translated the program into C and got rid of read by using getchar/ungetchar.
It's been great fun and now I'm kind of stuck a bit at the point of implementing macros. I have a simplistic version in C but want to remove that again --I like the idea of having the absolute minimal LISP interpreter in C-- and only introduce macros after having bootstrapped into the LISP/Mes domain.
Greetings,
janneke