RE: [Algorithms] Scripting

[Jason D. <jas...@bl...>]

  That'd be wonderful if my message hadn't been preceded with "for a console
project I worked on".  It was for the original PlayStation, and while doing
code overlays was something we initially looked into, it was a bugger to get
right.  With no operating system to help us, either all the code would have
to be compiled to start at the same address, we load and fix all jmp / jsr's
ourselves, or we used scripts.  We went with scripts.

  As I said, it's not for everyone.

Jason



-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of Phil
Teschner
Sent: Wednesday, March 28, 2001 2:37 PM
To: gda...@li...
Subject: RE: [Algorithms] Scripting


Just to throw some fuel into the fire:

Couldn't you just have loaded c/c++ code dynamically.  There's nothing
that says you can't load/unload code at run time.

Certainly in Windows you can do this through LoadLibrary/FreeLibrary and
GetProcAddress methods.

This requires a standard known interface between these libraries and
your code, but you have to have that with "real" scripting languages.

This also means you can compile these things while your game is running
and the link step should be fairly minimal (which means you can do
iterative programming without exiting/entering the game).

The drawback is that you don't get compiler warnings when you
incorrectly use the functions that you got via GetProcAddress.

The other drawback is that it is c/c++ and not something higher level.

Phil

-----Original Message-----
From: Jason Dorie [mailto:jas...@bl...]
Sent: Wednesday, March 28, 2001 2:19 PM
To: gda...@li...
Subject: RE: [Algorithms] Scripting


  For a console project I worked on a couple years ago we needed
loadable
code for AI (too many unique behaviors took up too much RAM).  We
implemented our own virtual machine, and used YACC and LEXX to create
the
language.

  The VM was pretty simple - it had 32 general use registers, a stack,
and
about 12 basic instructions (add, sub, cmp, jsr, jmp, jmp on
condition...)
and a bunch of game specific ones.  All the native code we wanted could
be
implemented as instructions in the virtual machine, and it was actually
pretty elegant.  It took two people about a week to get it running.  The
VM
itself was written as a class, so multiple VM's could be running at the
same
time, and debugging was pretty easy because you had full access to the
registers (class members), call stack (linked list), and could watch the
machine evaluate the code.  We could tell the machine to execute 100
instructions, execute until a JMP was called (new state), etc...  It was
pretty cool.

  I wouldn't recommend it for everyone, but it was worth trying, and the
result was fast.

Jason




-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of
bmarshall
Sent: Tuesday, March 27, 2001 1:51 AM
To: GDA...@li...
Subject: [Algorithms] Scripting


Anyone have any experiences with runtime scripting that they are happy
to
share. I'm looking at alternatives for scripting level setup, menus etc
for
a game. I 'm thinking about either something like Java or Perl. The main
emphasis being on good editing/debugging support over speed as critical
functions/queries will be in native code.

Any thoughts appreciated, but please guys I don't want to start a Java
vs.
Perl vs. whatever flamer war!

Thanks,
	-Brian.

Brian Marshall
Rare Limited,
Manor Park,
Twycross,
Warks,
England,
CV9 3QN
Phone: +44(0)1827 883400


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