On Thu, May 7, 2009 at 11:29 AM, Yoshiki Ohshima
<yoshiki@vpri.org> wrote:
At Thu, 7 May 2009 11:09:32 -0700,
Eliot Miranda wrote:
>
> > - remove stack access from the API, writing them as SmartSyntaxPlugins where arguments are passed in as
> parameters,
> > returning the result on success and 0 (not SmallInteger 0) on
> > failure
>
> In these days, nobody would care much about it, but this would
> make it harder to simulate a platform independent performance primitive in the image?
>
> I don't think it makes any difference. In the simulator the VM could e.g. use perform:withArguments: to invoke the
> primitive. The real VM needs to do something similar and have glue to the platform's native calling convention, which
> can be as simple as a 32-element switch statement:
> switch (numArgs) {
> case 0: result = primitiveFunctionPointer(stackTop()); break;
> case 1: result = primtiveFunctionPointer(stackValue(1),stackTop); break;
> ...
> or as sophisticated as machine code generated on the fly.
What I mean was to debug the Slang-ish code in the Smalltalk
Debugger. Putting "halt" in the primitive code in Slang and doing
#doPrimitive: lets you do it, but code written in
SmartSyntaxInterpreter syntax doesn't do what it says so Smalltalk
debugger cannot handle it. But again, this is a minor issue now.
Ah, OK, now I get it. I think we can fix this. If the type information is moved into pragmas then I think the debug issue can be made to go away. the simulator would have to read the pragma and type convert before it called perform: but I think this is straight-forward. The pragma could be e.g. performable by the VM to do the type conversion.
> > - provide isImmediateObject: and use it in place of isIntegerObject: when the objective is to select heap objects.
> Use
> > isCharacterObject: when the objective is to select a character. I
> > intend to add immediate characters within the next few months.
>
> Are you going to use UTF-32 or UTF-16 for it?
>
> Characters would be Unicode code points (WideString is UTF-32 right?). UTF-16 is a variable-length string encoding.
> Presumably there will be primitive converters to/from UTF-16 to WideString.
Yes, among these choices, my vote would be for UTF-32 (for 21-bit
space). But variable-length-ness doesn't really go away when even
when using UTF-32, as there are composition characters.
Alternatively, we could go for all UTF-8 in image representation for
Strings (as a data buffer) and when you need a Character, create an
instance, or return the one in a table, that is in UTF-32. And in the
image side, displayable "String" should (almost) always accompany the
attributes like Text.
I'm a bit out of my depth here. I would have thought that you would want the basic string types to be fixed width for fast accessing, simply because variable length doesn't scale to e.g. indexing 1 megabyte strings. But that for the platform interface one would want efficient conversion to/from fixed and variable length encodings. But that's just my gut. I expect I'll implement whatever y'all say makes sense.
-- Yoshiki