Okay, I'm thinking the core will have four distinct perl variable types
internally:
* Scalar
* Hash
* Array
* List
Scalars, hashes, and arrays are pretty much what you'd expect. Lists,
though, are the interesting bit.
The big reason for them is efficiency--we're basically deferring
flattening. It means, for example, that if someone does this:
my @foo;
@foo = bar();
sub bar {
my @arr;
$arr[time]=14;
return(@arr, 12);
}
the return from the sub is actually two elements rather than a zillion, and
the final assignment of the return boils down to an array rehoming with a
push on the end. There are other useful cases, for example this:
($foo, $bar) = (@baz, @xyzzy);
wouldn't go flatten anything, just snag the first two elements of @baz, or
whatever's needed from @xyzzy if @baz isn't big enough. If an element of
the list isn't used then it's never evaluated.
Active data, for example function calls, would always be evaluated (though
if it returns a list that list would be substituted in rather than
flattened) since perl does guarantee that happens.
The part I'm waffling on (and should ultimately punt to Larry) is what to
do with lazy data, and what exactly counts as lazy data anyway. For
example, tied variables certainly aren't passive data, but should they be
evaluated if they aren't used? If you do this:
($foo, $bar) = (@baz, "12", 15, $some_tied_scalar);
should the FETCH method of $some_tied_scalar be called unconditionally,
even though we don't use it? (I'd argue yes, but prefer no... :)
Also one side-effect of this, if we allow it, is to have a list masqerade
(under the hood, at least) as another variable type. We could, say, see this:
@foo = (@bar, @baz);
but actually defer evaluating the list and doing the assignment until
either @foo, @bar, or @baz is accessed. (Potentially holding off even
further--things like scalar() on @foo, for example, wouldn't require
finishing the assignment, and neither would something simple like $foo[12])
Anyway, that's what I'm thinking about at the moment. Comments? (Keeping in
mind that we can't really decide things that are perl-visible without the
OK of Larry)
Dan
--------------------------------------"it's like this"-------------------
Dan Sugalski even samurai
[EMAIL PROTECTED] have teddy bears and even
teddy bears get drunk
