Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!oliveb!pyramid!athertn!paul
From: paul@athertn.Atherton.COM (Paul Sander)
Newsgroups: comp.sys.apple
Subject: Re: P-Code System
Summary: Run-time support need not be large
Message-ID: <5023@athertn.Atherton.COM>
Date: 2 Jun 89 20:11:31 GMT
References: <8905311619.AA04801@crash.cts.com>
Organization: Atherton Technology, Sunnyvale, CA
Lines: 34

In article <8905311619.AA04801@crash.cts.com>, nelson@pro-europa.cts.com (Nelson Minar) writes:
> What are the performance characteristics of a P-System? Isn't the kernal
> rather large? What sort of ballpark execution speed are we talking? Maybe 50%
> of assembled code?

Runtime support need not be large.  No matter what we write, we'd need things
like multiple-precision arithmetic (on a 6502, even 16-bit adds are double
precision, but we all know that), string I/O, and so on.  None of these things
by themselves is large, and everything put together is only a couple of Kbytes.
For example, Fig-Forth runs in less that 8K, I think, and I've implemented a
Pascal subset that uses a P-code interpreter that runs around 4K (unoptimized).
I've made no attempt to measure performance, but for what I do with the stuff
the performance is reasonable (maybe even fast).

> Also, I know there are a couple of P-Systems already out there - Beagle Basic,
> various Pascals. Any sort of P-system source code one could use (legally) as a
> starting point?

Try checking Byte's back issues.  August 1978 (I believe) contained the first
of three articles that implemented a Pascal subset compiler in BASIC that
produced P-code.  Also included are Pascal source for a debugger, and some
other stuff like loophole optimization techniques.  Perhaps someone could
use that as a starting point (with the articles' author's permission, of
course).

> toth's point is well taken - a slow system is better than no system.

There are times when slow systems are worse than useless (i.e. manual systems
are faster and work better for the task at hand) but IMHO this is not one of
them.
-- 
Paul Sander        (408) 734-9822       | If a machine is powerful enough
paul@Atherton.COM                       | to have a DWIM button, why bother
{decwrl,sun,pyramid}!athertn!paul       | with the button?  -- Eric Black