Re: Thoughts and Opinions or something like that

[Jerzy Karczmarczuk <karczma@info.unicaen.fr>]

"chris.danx" wrote:
> 
> Hi, [posting to others //nsgroups Ada & misc// re-instated]

(As you wish, but it has NOTHING to do with Ada, etc... And, anyway,
I don't read those newsgroups, so if somebody is kind enough to comment,
it won't reach me)

I remarked, concerning the "problems" with VMs

> > Scheme VMs have GC and tail-call optimization. Java VM has threads.
> > Icon VM has coroutines (rather: co-expressions). No problems, and
> > I would add that it is MUCH easier to provide for a more complicated
> > semantics of a language using an interpreter than compiling to
> > a native code...

> Do you mean just rip out an interpreter and forget the VM idea 
> until later? That sounds like a good idea.

I think that there is a small misunderstanding here. An interpreter
IS a Virtual Machine. I just said that in general the idea of building
a language with interesting semantic layer is easier if one has some
higher-level executable code, not the assembly stuff, that's all. So,
if I wanted to construct a language, I would build an interpreter first.
A virtual machine, if you prefer. My own, not the Java stuff...

Alain Fisher proposes to look at the Smalltalk machine. Yes, it is
quite powerful, and nice. However, the object-orientation is build
at a low level, and if you don't need it, there will be a cost.

There is plenty of small VMachines around. From Forth/Postscript,
through the SECD models (including lazy or persistent), the CAMLish
kernel used e.g. to implement Moscow SML, logical machines such as
variants of WAM, etc. One can learn a lot from them, even if there
is not much sense in "ripping" them, and adapting to a novel
language. In particular one may learn how to implement tail-recursion
and something about GC.



> > > -    Lists                         []
> > > -    Arrays                        <>
> >
> > Don't neglect reasonable arrays, please, otherwise one day, sooner
> > or later you will regret it...
> 
> What do you mean by reasonable arrays?  What's unreasonable about them?
> 
> Chris

Not about THEM.
There are unreasonable arrays simulated by lists. Reasonable mean:
real arrays, secure (index checking), true random access, working well
with garbage collector (in some Lisps lists were dynamic, but arrays
static...), and fast iterators. 



Jerzy Karczmarczuk
Caen, France