[virtmach] Definition a virtual machine ?

[Francois-Rene Rideau]

>: Laurent Martelli

> How would you define a virtual machine ?
A virtual machine to me is just another name for a calculus;
i.e. some stuff with a semantics (preferably an operational semantics;
preferably one that can be effectively implemented).

> I'd say that any API can be considered a virtual machine.
Beware! An API usually refers to a library of interfaces,
which I would classify as a virtual machine *mixin*, not a full-fledged
virtual machine. Although I agree that a virtual machine may very well
be described in terms of an abstract grammar (whose nodes are roughly
categorized by an "API"), without any specification for the underlying
representation of syntax trees.

> Having byte-coded instructions is just an implementation issue of the VM
> after all.
Sure. See how David Halls used Scheme source SEXP as his portable and
flexible "virtual machine" for his Tube mobile code system (ahem; his
former home page where he published his PhD thesis is missing, and he
didn't answer to my message to his new address daveh@persimmon.co.uk).

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