Trailing-Edge - PDP-10 Archives - clisp - clisp/flavors/notes.txt
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The files in this directory should allow you to bring up a reasonable subset of
Symbolics v5.0 Flavors portably.  Some amount of minor hacking will need to be
done in order to interface your own system to instances, e.g. to make TYPE-OF
of an instance return its flavor-name.  More complicated hacking needs to be
done to make sending a message fast; ideally SEND is in microcode.

Symbol-macros are what implement instance variables portably, by analyzing
method code.  The portable macro (in symmac.slisp) that implements this is slow
and probably not yet bug-free (especially since the current version is untested
- I don't have access to a system providing environments).  However, hacking
symbol-macros into our (Spice Lisp) interpreter and compiler was easy and even
fun.  Of course, it helped that both were fairly simple and well-organized.

The kernel is the extremely hairy part of the system.  Its basic function is to
hide the implementation of instance variables and the various method machinery.
Most of what might be changed for efficiency's sake has been separated into the
kernel-kernel (pkkernel for portable).

The kernel-kernel (or pkkernel, for portable) implements the instance datatype.
All minor hooks into the system appear at this level.  The printer,
type-system, and optionally the fasloader may be changed to know about
instances.  The purpose of separating this out is so that other systems might
use the same hooks.

The file flavors.slisp uses the kernel and kernel-kernel.  I haven't bothered
to "correctly" implement all the various hacks that save one microcycles, but
if anyone wants to spend the time, I may accept the changes into future
releases.  I'm currently working on a document that describes the differences
between this and v5.0 Symbolics Flavors.

The file Vanilla.slisp contains all the default defined combinations and the
vanilla flavor definition.  You might want to add the "magic number" to the
print-self routine, among other things.  Note that since this uses flavors, you
have to (compile and) load the other files before compiling or loading this.