[z-machine] [Inform mntce] The Z-machine and Informs 6 and 7

[David Kinder]

Graham Nelson wrote:

 > Inform 6.31 is undergoing maintenance, and we're looking
 > around to see what it needs before it can be released:
 > testing, seems to be the answer.

Well, and there's some worry about the library changes Cedric made.
One possible approach would be to just update the compiler and not
the library, but before doing that it would be good to scan the CVS
history to see if any of the compiler changes are tied to library
changes.

 > That said, I currently have three preoccupations about Inform and
 > the Z-machine:
 >
 > (a) I would like better and more transparent Unicode support.
 > Ideally, I6 should read a UTF-8 input file and write a story file
 > which an interpreter with one of the "big" fonts would simply get
 > right. I've largely forgotten the issues involved, but I have a feeling
 > that it isn't completely trivial, and there are awkward dictionary
 > issues involved. I just feel that any 21st-century Z-machine ought
 > to understand Unicode. This might need careful thought.

I don't think that this is too hard a problem, overall. On the Z-machine
level, the specification provides reasonably decent Unicode support, I
think. My understanding of the remaining problems:

1) Dictionary resolution. Having only 9 bytes of dictionary resolution
causes lots of problems when you try to use lots of different characters
in dictionary words. Sam's V9 work has a solution to this, and in fact is
probably my favourite bit of V9: it just allows longer dictionary entries.

It occurs to me that perhaps this variable dictionary length could be moved
from V9 into Z-Spec 1.1, maybe?

2) Arbitrary Unicode output. Earlier Z-Spec revisions had a scheme for
printing out any Unicode character sequence embedded in a string, though
after debate it was dropped from the last version. Perhaps it should be
brought back.

3) Compiler support. Most of the work is in getting I6 to cope with Unicode
input. The idea of translating Unicode input to @{xxx} style input seems
feasible, though the error messages might be tricky. Still, if we're worrying
more about I7 than I6, I suspect we can live with it.

 > (b) It is time, in my view, to make Blorb more or less compulsory.

Yes. As Jason said, this used to be in Z-Spec 1.1. I think it should just
be a requirement.

David