A first look - some comments

[Peter Hugosson-Miller]

Brian T Rice wrote:

> On Fri, 5 Sep 2003, Peter Hugosson-Miller wrote:
>
>> there is a method in life.slate that is
>> defined but never used, can you find it?
>
>
> Well, I wrote it, so I probably shouldn't just give away the answer (which
> I did just verify, to be sure). ;)

<Grin!> And while I'm on the subject, in order to make the program work 
correctly in Smalltalk, I had to change the #new method, so that cells 
and newCells were different objects, by setting newCells to be a copy of 
cells (which I guess,  in Slate, might be): "newG newCells: newG cells 
clone". Without this change I got a different behaviour from the normal 
Life Game, which never settled down into the familiar patterns of the 
original. Was this a bug in your code, or is there a subtle difference 
in the handling of arrays that I ought to know about?

>> I must not be understanding something about the multiple
>> dispatch, because I can't see anything in the above preventing message
>> cascades from being used, like in the Smalltalk version. I think I would
>> miss them too, as they are so useful in init methods.
>
>
> Well, the truth is that /all/ arguments in a message-send in Slate are the
> receivers. They're being asked to cooperate in a behavior, so to speak.
> The PMD paper (http://tunes.org/~eihrul/pmd.pdf) explains the basic
> metaphor anyway (although the lookup description is outdated). So,
> although we also do prefer cascades for clarity, it seemed at odds with
> the basic language metaphor to not treat the left-most argument specially.
> However, arguments to the left do receive greater precedence, so this
> reasoning isn't ironclad.

OK, I read the paper, and I think I get the basic idea. At each method 
invocation you start with a clean slate, put all the concerned variables 
on it, together with the selector, then work out exactly which method to 
call based on which most closely matches the types of the variables in 
the given positions. But you are still probably going to use a stack as 
that clean slate, and you have to push them in some order, which would 
most logically be the "receiver", followed by the "arguments", so you 
can take account of precedence. So if you wanted to have message 
cascading this could be organized by the compiler first pushing an extra 
copy of the "receiver", doing the PMD-related stuff, then popping and 
discarding the result. This would not affect the PMD mechanism, as that 
all happens at runtime.

> I should mention that ";" has been re-used as a binary operator, for
> concatenation and stream-writing, and works well that way, so it's not
> trivial to go back.

I would have no problem with using a different character as the cascade 
indicator, if it meant I could write more concise code. It's a different 
language after all, even if the syntax looks a bit like Smalltalk. I 
personally don't like the work-arounds you suggested, but it just might 
be that I have been cleaning up other peoples code for too long, and 
have the typical Smalltalk idioms "in my blood" :-). I guess one could 
get used to the Slate way too, given practise.

> Also, a lot of this systems-setup code with adding and setting slots and
> such is supposed to be done visually at some point (when I get the system
> support up to the needed levels). Unfortunately, getting to that level
> obviously takes a lot of time and work, but that's what is in mind.

For browsers and such, I guess one could take a look at Squeak for 
inspiration. I believe it to be the Smalltalk dialect that has been 
ported to the most platforms, and if Slate is to propagate it needs to 
be available for as many people as possible, as early as possible. Doing 
all the widgets in Slate would speed up this process, as you wouldn't 
have to write any platform-specific code once you had the basic 
bit-blast working. Native widgets would then emerge naturally from the 
community as the number of Slate enthusiasts reached the critical mass. 
At least, this is what seems to be happening in Squeak.

Sorry for this long and not very helpful post, but Slate interests me, 
and I hope that it has a future. I think it's time for to try and get 
Slate running so that I know a bit more what I'm talking about...

-- 
Best regards,

Peter Hugosson-Miller
"Quidquid Latine dictum sit, altum viditur."