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Re: [netlabs #801] [PATCH] PerlArray in scalar context

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Sean O'Rourke
August 25, 2002 09:57
Re: [netlabs #801] [PATCH] PerlArray in scalar context
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I ran across this in looking at tidying up old bugs.  It seems like things
are backwards below -- hyper-operation is a language-level shorthand for
iteration over a container, so there's no reason for the container's
vtable methods to be "hyper".  Actually, it seems like there are at least
a couple ways in which pushing this responsibility onto vtable methods may
not be the best way: if we "hype" non-vtable methods, we have to handle
explicit iteration in bytecode; and if we hyper-operate on tied variables,
they have to re-implement this looping behavior in their add, etc methods.

It looks like the standard perl5 behavior is implemented by the current
vtable methods (hyping done separately), but I wanted to make sure we were
on the same page before closing the bug.


On Wed, 14 Aug 2002, David M. Lloyd wrote:
> [what PerlArray vtable methods should do for "$x = @a + @b"]
> I thought about this more.  Here's a brain dump:
> Here's how I'd expect these expressions to be executed internally, in
> gross pseudocode, ignoring for the moment the multimethod vaporware:
> $r = $a + $b;             # $a->add($a, $b, $r)
> $r = @a + $b;             # $t = @a->get_pmc(@a); $t->add($t, $b, $r)
> $r = $a + @b;             # $t = @b->get_pmc(@b); $t->add($a, $t, $r)
> $r = @a + @b;             # $t = @a->get_pmc(@a); $u = @b->get_pmc(@b); $t->add($t, $u, $r);
> @r = $a ^+ $b;            # Something that makes one-elment arrays and
>                           # uses add method on array object?  Or perhaps
>                           # error
> @r = @a ^+ $b;            # Does this distribute? If so,
>                           # @a->add(@a, $b, @r) else see above
> @r = $a ^+ @b;            # See above
> @r = @a ^+ @b;            # @a->add(@a, @b, @r), easy

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