At 01:20 PM 12/7/00 +0000, David Mitchell wrote:
>Dan Sugalski <[EMAIL PROTECTED]> wrote:
>
> > print $foo[0];
> > is
> > foo->get_string[UTF_8](ARRAY, 0);
> > while
> > print $foo
> > is
> > foo->get_string[UTF_8](SCALAR);
>
>Just to clarify:
>
>does the get_string method in an AV's vtable do an indexing lookup,
>grab the relevant SV pointer, then call that SV's get_string() method,
>and forward the return value? ie
>
>char * AV_get_string_utf8(AV *av, int index) {
> SV* sv = av->whatever[index];
> return sv->get_string[UTF_8](sv);
>}
>
>What advantage(s) does this buy?
It means that array and hash elements don't have to be scalars, and that
the scalar fetch/store opcodes don't need to check array and hash types.
One of the memory use wins that Chip talked about with Topaz was having
specialized array and hash types--string, integer, and float arrays were
the big ones. If you do this (and lots of folks do)
my @foo;
@foo = <SOME_HUGE_FILE>;
then having @foo be a specialized array that only holds strings (requiring
a declaration, of course) is a memory win. Those array elements don't have
to be pointers to scalars--they can be pointers to strings, tossing all the
unneeded scalar bits. And while scalars might be slightly slimmer in p6,
there's still non-string bits that we can toss, along with possibly a level
of indirection in there. (The array could hold all the string info and not
even have to hold pointers to each string's info)
>I can see some obvious disadvantages here - AV implementers have to
>include a whole bunch of boilerplate code for methods which are of
>no concern to them, and lots of parameters and return values have
>to be passed back and forth unnecessarily.
Which is one of the places that good inheritance can come in handy. I'm
also thinking it's a place (vtable coding in general) where the PIL would
be a big win. (Both in the table definitions and in the routines for the
tables)
Dan
--------------------------------------"it's like this"-------------------
Dan Sugalski even samurai
[EMAIL PROTECTED] have teddy bears and even
teddy bears get drunk
