Well, I had the right idea, but at a key moment I zigged when
I should have zagged. So let's try this again.
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On Wed, Nov 23, 2005 at 10:49:18PM +0100, Leopold Toetsch wrote:
> outer_sub - (the static sub PMC info) can't refer to :outer because the
> :outer can be a closure too. There are many incarnations of the :outer
> then. Therefore the implementation needs sub->ctx (currently and IMHO).
The docs accidentally conflate non-closure Subs and closure Subs. So
I'm going to write my way through this. I think the design as is can
work, with each Sub having a static outer_sub attribute, but only if
closures also have an attribute that points to the Sub that they were
created from.
(Perl 5 calls this closure-creation process "cloning". I'll adopt
that term for this doc, and maybe permanently.)
OK, here goes. Correct me where I go wrong:
* The initial static result of compilation is N Parrot_subroutines
(Subs).
* Each of these Subs may have a non-NULL outer_sub attribute, which
describes the textual relationship of the Subs in the original
source code. For example, given:
sub foo {
my sub bar {
my sub baz {
}
}
}
baz.outer_sub is bar, and bar.outer_sub is foo.
* This is a static description of a static situation (the source code
doesn't evolve at runtime). So it need never change.
* The result of newclosure is a new Sub, but I'm going to call it a
Closure for clarity in this message.
* Each Closure has an "outer_ctx" attribute, which points to the
call frame in which it was cloned. That call frame contains a
pointer to the Sub (or Closure) that cloned the leaf Closure.
* Therefore, we have outer_sub for the relationship of non-Closure
Subs, and caller_ctx for Closure (cloning) relationships.
* And thus there should be no need to modify a Sub after compilation,
nor a Closure after cloning.
Does this describe the current situation and its features?
--
Chip Salzenberg <[EMAIL PROTECTED]>
