On Fri, Aug 11, 2006 at 04:38:59PM -0400, Charles Reiss wrote:
> On 8/10/06, Chip Salzenberg <[EMAIL PROTECTED]> wrote:
> > /* XXX is it okay to combine flatten/slurpy into one flag? */
> >
> > The answer is "No": "flat" is an output flag, "slurpy_array" is an input
> > flag, and there's no guarantee that the input and output flags won't
> > conflict with each other. So I guess this means that something has to
> > change.
>
> I suppose trying to make '@' mean something different for signatures and
> for calls from C (as I have done) is a Bad Idea as long as the same code
> is used to parse the signatures in both cases. The easy solution is to
> choose a character other than '@' for one of the directions though I can't
> think of what might be most natural ('F' for flat?).
To provide a general ability to wrap any call from C, then you need to add
named parameter support too; flat arrays are _so_ Perl 5. Would '%' and 'N'
work for you? :-) (also see below)
> >MORE QUESTIONS
> > * The '@' character for native call signatures is new, and AFAICT is just
> > syntactic sugar, since the caller could do the array creation himself.
> > Could you explain what you would have to do if you didn't introduce this
> > feature? (I'm not necessarily against it, mind you, I just want to know
> > what the deal is.)
>
> It is just syntactic sugar. So, not using would be as you describe, having
> the (most likely PIR) caller construct the array manually. My use of this
> feature is only to allow naturally passing an arbitrary number of
> arguments to the subroutine that is first executed in a new thread, which
> I feel is quite convenient.
Well, as it happens, we've been wanting support for variadic PMC METHODs for
a Long Time. Since you're already introducing necessary infrastructure, are
you inclined to add some PMC METHOD syntactic sugar too, so that we can
conveniently define METHODs that accept arbitrary parameter lists? (This
is not a merge blocker, of course; just a wishlist item.)
> > * Another comment asks:
> >
> > # autogenerate for exotic types
> > # (XXX is this appropriate or do we want them to each
> > # be explicitly cleared to have the variant?)
> >
> > Well, that depends. Is there currently any way for a named METHOD to
> > specify whether it is :write, and if so, is this used? If so, then yes,
> > making an automatic ro variant is OK. If not, then I think we might
> > want such a thing...?
>
> The read-only variant generation currently does not handle NCI methods
> at all. There are number of implementation options; the best I can
> think of is to override findmethod (in the read-only type) to check
> for a property on the found method PMC that would indicates it writes
> (or vice-versa).
That's actually kind of neat; at least, it's clearly the least bad of all
the options I see.
The only minor downside IMO is that in order to get adequate speed we'll
need to dedicate an easy-to-see flag bit somewhere visible in the method PMC
to mean ":write", and there are only so many of those. But fast threading
is hardly a minor feature, so I don't mind that cost at all.
> A bigger issue for automatic read-only variant generation is that MMD
> methods currently don't do any read-onlyness detection. (Sorry!) (This is
> not quite as much as a problem as it may seem because things like String
> and Integer, being designed to allow subclassing, call vtable methods from
> their MMD methods to do any manipulation.)
Understood, agreed.
> As a stopgap solution, it would be easy to reverse the logic I have
> now and default to not generating a read-only version except when the
> .pmc file says it is okay instead of the other way around.
Well, this is still 0.4, not 1.0. If you can just tell us on the list what
we shouldn't do, so we can include it in the release notes, then I don't
mind having only partial protection. For obvious reasons, nobody's using
the thread support right now, so it won't break anything. ...Or will it?
--
Chip Salzenberg <[EMAIL PROTECTED]>
