[self-interest] Re: Self bytecodes

[Douglas Atique]

If it can be freely distributed, as Self 4.0, it would be a good idea to have
this available.
Douglas

David.Ungar at Eng.Sun.COM wrote:

> When I was working on the interpreter, I also added a POP bytecode.
> If I can release the lastest Self VM, folks out there could have it.
> Would there be any interest?
>
> - Dave
>
> At 4:38 PM -0400 5/31/99, Stefan Matthias Aust wrote:
> > >It all seems fine, but I don´t understand something seemingly
> >>straightforward: knowing that in a send the receiver and arguments are
> >>popped off stack and the result is pushed onto stack, how is the number
> >>of arguments of a send determined, so that my interpreter could know how
> >>many pops it should make?
> >
> >You can derive that from the selector symbol.  Unary selectors (that are
> >selectors composed from letters - especially the first character must be a
> >lowercase letter - without ':' in it) need no arguments at all.  Binary
> >selectors (that are all selectors which neither start with a letter or with
> >an '_') have exactly one argument.  For keyword selectors (which are
> >composed of sequences of letters (and digits) that end with a colon ':')
> >simply count the number of colons.
> >
> >A different problem is to know when to pop returned objects from the stack
> >which aren't used.  I think, you cannot detect that and simply adjust the
> >stack when you leave the method.  Here's an example:  3+4. nil
> >
> >This will generate something along:  push 3, push 4, send #+, push nil.
> >
> >The + method for integers will pop both 3 and 4 from the stack and push the
> >result, 7.  However, this object isn't needed and will use one stack slot
> >upton the method returns (with nil).
> >
> >There might be a way to notice that "7" isn't used anywhere in the method,
> >but that's probably to much work for an interpreter.  A compiler that will
> >create and analyse a complete parse tree for each method can do this.
> >
> >
> >bye
> >--
> >Stefan Matthias Aust // Truth Until Paradox!
> >
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>     David Ungar
>     Sun Microsystems Laboratories
>     (650) 336-2618
>
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