Dan Sugalski wrote:
> First, of course, runtime and compiletime are mixed on perl. String eval
> has to go walk back up the pads *at runtime* and resolve the variable names.
Sure, if you use eval, the symbol table for the current scope
needs to be available. There's no reason to have more than
one though -- all instances of an activation record share
the same symbol table.
For the common case when we aren't debugging and a sub doesn't
use string eval, it would be nice to use less memory and drop
the scope's symbol table.
> Second, Larry's decreed you'll be able to look up lexicals by name using
> the MY hash. And look up at outer levels. How do you plan to look up
> variables by name when you're peering outside your compilation unit? With a
> key that can be resolved only at runtime?
I've searched for the definition of %MY, but all I can find is
a reference to a pseudo class MY. I don't read those as being the
same thing. It seems like "pseudo class MY" is intended as a
compiler extension API. The %MY hash could sort of do that (if
we wrapped all the access with BEGIN blocks), but it doesn't
feel very consistent with lexical variables.
Is %MY (with attributes presumably) really going to be the API
to the symbol table? Why don't we just have *one* API to the
symbol table and use attributes to differentiate between dynamic
and lexical scoping?
> >That's a huge difference over emulating "my" with "temp" like
> >what was originally proposed!
>
> That, oddly enough, is doable with enough compiler work. A silly thing, but
> doable. It's irrelevant to the question as it had evolved, namely "what's
> the difference between a stash and a pad?" We could, after all, associate a
> new stash with each level of lexical scope if we were so inclined. Or make
> stashes and pads identical under the hood and just reference them differently.
These things behave totally different in a closure though.
A "temp" variable must have its' global binding restored when
returning to the caller. But that leaves closures referencing
the wrong variable.
Anyways, since you say "oddly enough" and "silly thing", I suspect
that you're aren't doing it this way. ;)
- Ken
