Re: on bootstrapping: introducing Mes

[ludo@gnu.org (Ludovic Courtès)]

Hi!

Jan Nieuwenhuizen <janneke@gnu.org> skribis:

> I have a minimal LISP-1.5-resembling interpreter in C that now can
> also interpret itself
>
>     https://gitlab.com/janneke/mes
>
> It 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.

Sounds fun!

> 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 1) with a pointer to
> the 1962 LISP 1.5 paper by John McCarthy 2).
>
> 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.

From a bootstrapping viewpoint, since Mes is in C, we’re back to the
same problem we have with Guile.  :-) Guile has an interpreter written
in C, for bootstrapping purposes, and it’s capable of running any kind
of Scheme code, I think, including the full macro expander.

To make the bootstrap Guile smaller, maybe we could remove .go files
from it and build them as the initial step.  That would be comparable to
the strategy you suggest, I think.

Cheers,
Ludo’.