At 12:35 PM 8/4/00 -0400, Chaim Frenkel wrote:
> >>>>> "DS" == Dan Sugalski <[EMAIL PROTECTED]> writes:
>
>DS> The language semantics of tie strongly impact the internals. tie() is
>DS> basically a declaration that the rules are completely different (and
>DS> unknown at compile time) for the tied variable. Shoots down
>optimization a
>DS> bunch, since access to a tied varible has to be treated as a function
>call
>DS> rather than as access to data with known behaviours.
>
>Why?
>
>The vtbl for a tied variable would do all the work. Either the pointer
>is to a springboard into perl code, or internal code, or the XS
>replacement code.
It's more than that. If the optimizer does code flow, it can know that
$foo's been assigned an integer, for example, and maybe even that that
variable's never been changed, so this:
$foo = 12;
$bar = something();
$bar = $foo;
could work out to:
$foo = $bar = 12;
something();
Where if you tie, we have *no* idea what you're doing. This:
tie $foo, SomeModule;
$foo = 12;
could well reboot some server in outer mongolia for all we know. Tied
variable access counts as a function call, which smacks optimization all by
itself.
Dan
--------------------------------------"it's like this"-------------------
Dan Sugalski even samurai
[EMAIL PROTECTED] have teddy bears and even
teddy bears get drunk
