Path: utzoo!attcan!uunet!mcsun!unido!tub!net
From: net@tub.UUCP (Oliver Laumann)
Newsgroups: comp.lang.scheme
Subject: Scheme implementation strategies (was: Free Macintosh Scheme)
Message-ID: <1436@tub.UUCP>
Date: 15 Jul 90 13:04:46 GMT
References: <601@argosy.UUCP> <5598@hplabsz.HPL.HP.COM>
Reply-To: net@tub.UUCP (Oliver Laumann)
Organization: Technical University of Berlin, Germany
Lines: 34

I can't answer the original question, but I would like to bring up a
general observation about Scheme implementations:

In article <5598@hplabsz.HPL.HP.COM> mayer@hplabs.hp.com (Niels Mayer) writes:
>
> Is it [Free MacIntosh Scheme] byte compiled??
> 
> Does it require any assembly language coding??

I think the latter follows from the former (or rather from the opposite).

In a Scheme implementation (written in C or a similar language) that
does NOT compile the source code to some form of "virtual machine" code
and then run a virtual machine to execute it, it is impossible to
implement call/cc without assembly language coding.

As far as I know, Elk is the only Scheme implementation with this
property, i.e. it directly interprets the source code AND supports
call/cc (this is due to the fact that it was written to be used
as a general extension language); thus Elk needs assembly language
coding (a few lines actually).

So generally speaking a programming language L may or may not have the
property

   ``A Scheme interpreter written in L that does not follow
   the "virtual-machine approach" can support call/cc''.

Assembly and (obviously) Scheme have this property (I don't know any
other that falls in this category); C, C++, PASCAL, and Lisp do not
have it.  Is that saying something?  I don't know...

--
Oliver Laumann     net@TUB.BITNET     net@tub.cs.tu-berlin.de     net@tub.UUCP